Re: [EVDL] Q about using an electronic load.

2014-11-08 Thread Zeke Yewdall via EV



 Well, there are grid-tie inverters down as small as 200W or so readily
 available, often down to 12v input.


 Yes, though the two I have (Trace Microsine and Enphase) won't work with a
 battery or DC supply as their input.

 As Lee said, just about all grid-tied microinverters are designed for a
current limited source, so there's a good chance that they'd have some
issues with a battery when they did the short circuit portion of their IV
curve sweep.  Some of the larger grid-tied inverters do have the ability to
change the parameters to handle non-current limited sources like wind
turbines or such, but I'm not aware of ability to change the software on
the microinverters.

Z
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Re: [EVDL] Q about using an electronic load.

2014-11-07 Thread Lee Hart via EV
Roger has some excellent advice here. It reflects a lot of what I do 
myself. :-)


Roger Stockton via EV wrote:

Thought I'd mention that while a programmable load is an *excellent*
way to discharge when testing batteries, it can be pricey...


Indeed. Programmable loads get very expensive if you are dealing with 
high power (high voltages and/or high currents). They are also effective 
room heaters. Good in Minnesota winters; but bad in Arizona in the 
summer when you're already paying to air condition.



If you already have a data logger or other means of
measuring/controlling a load and charger, then perhaps consider using
a passive load in parallel with a smaller electronic load, so that
you can save money on the electronic load purchase.

A simple QBasic program on an old laptop controlled the relay for
the load and another for the charger via the parallel port.


This is the approach I use. I have a couple of $50 DAQ118 analog/digital 
I/O modules that plug into my PC. They have several 12-bit analog inputs 
(to read voltages, currents, and temperatures), outputs (to throttle the 
charger, and digital output channels (operate relays to select various 
loads).


They are run by a PC with software written in QuickBASIC. I have an old 
PC that is too slow for anything modern; but has a parallel port and is 
rock-solid-reliable and can run tests for days.


These modules were bought in 2002. I'm not sure if they are available 
today, but there are lots of equivalents.


I also have a Keithley 576 Measurement and Control system. This is a 
stand-alone data acquisition controller. Rather tedious to set up, but 
lots of channels, high precision, and very versatile.


I use these with a commercial battery charger for charging, and a custom 
made load box that basically consists of a bunch of big power resistors, 
in a box, with a fan, and relays to select the load resistance in a 
stepwise 1-2-4-8 sequence.



I started out with a battery cycler setup consisting of a bank of 12VDC
Edison-base (household screw-type) light bulbs


Light bulbs are a good *and* cheap load resistor. :-) As Roger says, 
they have the useful feature of drawing a roughly constant current 
despite changes in voltage. This is a simple way to get an approximately 
constant load current despite the sagging voltage as the battery discharges.


I've used car headlights (about 4 amps each) and taillights (about 1 amp 
each) as load resistors for 12v battery testing.



A simple QBasic program on an old laptop controlled the relay for
the load and another for the charger via the parallel port.
An E-meter with the RS232 comms option provided voltage, current,
etc. measurements to the QBasic program.


This describes the most common load tester I use. I have a few E-Meters 
/ Link 10 / ProLink meters (all the same meter, but sold respectively by 
Cruising Equipment / Heart Interface / and now Xantrex). These measure 
volts/amps/watts/amphours/watthours/time/temperature and send the data 
to a PC via an RS-232 serial port. I have a QuickBASIC program that 
logs, plots, and prints the data.


The controller is an old Manzanita Micro Rudman Regulator. It has an 
output that switches a relay to select between charge and discharge, and 
trimpots to select the max and min voltage at which to switch between 
charge and discharge. This setup has been documented in the EVDL archives.


I also built my own stand-alone battery tester/cycler, which includes 
the charger, constant-current load, and metering for volts, amps, 
amphours, temperature, etc. It is documented at


http://www3.telus.net/nook/balancerland/cycler/index.htm

This stuff is not exactly hard to build yourself, either from scratch 
or cobbled together using whatever you have on hand. But it does take a 
fair amount of time and effort to sort it all out and figure out how to 
use it.

--
A designer knows he has achieved perfection not when there is
nothing left to add, but when there is nothing left to take away.
-- Antoine de Saint Exupery
--
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Re: [EVDL] Q about using an electronic load.

2014-11-07 Thread Michael Ross via EV
Thank you , Lee.

Some concerns about cost may drop away because I am not aiming at
automotive EVs - for now , maybe never.

Because I need to go for some grant funding, I have to be aimed at
manufacturers - job creation is what everything is about these days (I
don't disagree).  The automotive manufacturers will likely build their own
labs.  But, the LEV (and smaller) market is in need of some help.

I think electronic loads are a good idea, but I will have to roll my own
stuff for a while; that will be a good learning experience I am sure.

Just guessing, I suspect I can do a lot with 50A of current and load.
 6000W is pushing 10 HP.  Electronic loads that size would be costly.

I need to sort this out better though.  I am trying to put together a
survey to collect information about testing people need but can't do,
testing they would far out if the cost was right, and so on.  I need a
range of packs sizes in this space.  I know there is still some lead acid
being used, so I probably need to consider that, but the arc of the future
is probably Lithium batteries.

I am already set up to use National Instruments DAQ and Keithley DMM
instruments.  I already program extensively in LabVIEW, so we will stick
with that (also the university has a site license for it).  We get an
academic discount on hardware and NI has an extensive array of choices.

I am still interested in seeing DIY setups - that is always very
instructive.




On Fri, Nov 7, 2014 at 12:30 PM, Lee Hart via EV ev@lists.evdl.org wrote:

 Roger has some excellent advice here. It reflects a lot of what I do
 myself. :-)

 Roger Stockton via EV wrote:

 Thought I'd mention that while a programmable load is an *excellent*
 way to discharge when testing batteries, it can be pricey...


 Indeed. Programmable loads get very expensive if you are dealing with high
 power (high voltages and/or high currents). They are also effective room
 heaters. Good in Minnesota winters; but bad in Arizona in the summer when
 you're already paying to air condition.

  If you already have a data logger or other means of
 measuring/controlling a load and charger, then perhaps consider using
 a passive load in parallel with a smaller electronic load, so that
 you can save money on the electronic load purchase.

 A simple QBasic program on an old laptop controlled the relay for
 the load and another for the charger via the parallel port.


 This is the approach I use. I have a couple of $50 DAQ118 analog/digital
 I/O modules that plug into my PC. They have several 12-bit analog inputs
 (to read voltages, currents, and temperatures), outputs (to throttle the
 charger, and digital output channels (operate relays to select various
 loads).

 They are run by a PC with software written in QuickBASIC. I have an old PC
 that is too slow for anything modern; but has a parallel port and is
 rock-solid-reliable and can run tests for days.

 These modules were bought in 2002. I'm not sure if they are available
 today, but there are lots of equivalents.

 I also have a Keithley 576 Measurement and Control system. This is a
 stand-alone data acquisition controller. Rather tedious to set up, but lots
 of channels, high precision, and very versatile.

 I use these with a commercial battery charger for charging, and a custom
 made load box that basically consists of a bunch of big power resistors, in
 a box, with a fan, and relays to select the load resistance in a stepwise
 1-2-4-8 sequence.

  I started out with a battery cycler setup consisting of a bank of 12VDC
 Edison-base (household screw-type) light bulbs


 Light bulbs are a good *and* cheap load resistor. :-) As Roger says, they
 have the useful feature of drawing a roughly constant current despite
 changes in voltage. This is a simple way to get an approximately constant
 load current despite the sagging voltage as the battery discharges.

 I've used car headlights (about 4 amps each) and taillights (about 1 amp
 each) as load resistors for 12v battery testing.

  A simple QBasic program on an old laptop controlled the relay for
 the load and another for the charger via the parallel port.
 An E-meter with the RS232 comms option provided voltage, current,
 etc. measurements to the QBasic program.


 This describes the most common load tester I use. I have a few E-Meters /
 Link 10 / ProLink meters (all the same meter, but sold respectively by
 Cruising Equipment / Heart Interface / and now Xantrex). These measure
 volts/amps/watts/amphours/watthours/time/temperature and send the data to
 a PC via an RS-232 serial port. I have a QuickBASIC program that logs,
 plots, and prints the data.

 The controller is an old Manzanita Micro Rudman Regulator. It has an
 output that switches a relay to select between charge and discharge, and
 trimpots to select the max and min voltage at which to switch between
 charge and discharge. This setup has been documented in the EVDL archives.

 I also built my own stand-alone battery 

Re: [EVDL] Q about using an electronic load.

2014-11-07 Thread Peter Gabrielsson via EV
One relatively cheap way of doing high power cycle testing is to cycle
power between a large battery bank and the test battery using a
bidirectional DCDC converter.

The DCDC is simple since it's just a switching pole with an inductor and
some controls. A DC motor controller with regen capability can be used as
the DCDC converter, the controls should have a constant torque (current)
mode for it to be useful.

On Fri, Nov 7, 2014 at 9:54 AM, Michael Ross via EV ev@lists.evdl.org
wrote:

 Thank you , Lee.

 Some concerns about cost may drop away because I am not aiming at
 automotive EVs - for now , maybe never.

 Because I need to go for some grant funding, I have to be aimed at
 manufacturers - job creation is what everything is about these days (I
 don't disagree).  The automotive manufacturers will likely build their own
 labs.  But, the LEV (and smaller) market is in need of some help.

 I think electronic loads are a good idea, but I will have to roll my own
 stuff for a while; that will be a good learning experience I am sure.

 Just guessing, I suspect I can do a lot with 50A of current and load.
  6000W is pushing 10 HP.  Electronic loads that size would be costly.

 I need to sort this out better though.  I am trying to put together a
 survey to collect information about testing people need but can't do,
 testing they would far out if the cost was right, and so on.  I need a
 range of packs sizes in this space.  I know there is still some lead acid
 being used, so I probably need to consider that, but the arc of the future
 is probably Lithium batteries.

 I am already set up to use National Instruments DAQ and Keithley DMM
 instruments.  I already program extensively in LabVIEW, so we will stick
 with that (also the university has a site license for it).  We get an
 academic discount on hardware and NI has an extensive array of choices.

 I am still interested in seeing DIY setups - that is always very
 instructive.




 On Fri, Nov 7, 2014 at 12:30 PM, Lee Hart via EV ev@lists.evdl.org
 wrote:

  Roger has some excellent advice here. It reflects a lot of what I do
  myself. :-)
 
  Roger Stockton via EV wrote:
 
  Thought I'd mention that while a programmable load is an *excellent*
  way to discharge when testing batteries, it can be pricey...
 
 
  Indeed. Programmable loads get very expensive if you are dealing with
 high
  power (high voltages and/or high currents). They are also effective room
  heaters. Good in Minnesota winters; but bad in Arizona in the summer when
  you're already paying to air condition.
 
   If you already have a data logger or other means of
  measuring/controlling a load and charger, then perhaps consider using
  a passive load in parallel with a smaller electronic load, so that
  you can save money on the electronic load purchase.
 
  A simple QBasic program on an old laptop controlled the relay for
  the load and another for the charger via the parallel port.
 
 
  This is the approach I use. I have a couple of $50 DAQ118 analog/digital
  I/O modules that plug into my PC. They have several 12-bit analog inputs
  (to read voltages, currents, and temperatures), outputs (to throttle the
  charger, and digital output channels (operate relays to select various
  loads).
 
  They are run by a PC with software written in QuickBASIC. I have an old
 PC
  that is too slow for anything modern; but has a parallel port and is
  rock-solid-reliable and can run tests for days.
 
  These modules were bought in 2002. I'm not sure if they are available
  today, but there are lots of equivalents.
 
  I also have a Keithley 576 Measurement and Control system. This is a
  stand-alone data acquisition controller. Rather tedious to set up, but
 lots
  of channels, high precision, and very versatile.
 
  I use these with a commercial battery charger for charging, and a custom
  made load box that basically consists of a bunch of big power resistors,
 in
  a box, with a fan, and relays to select the load resistance in a stepwise
  1-2-4-8 sequence.
 
   I started out with a battery cycler setup consisting of a bank of 12VDC
  Edison-base (household screw-type) light bulbs
 
 
  Light bulbs are a good *and* cheap load resistor. :-) As Roger says, they
  have the useful feature of drawing a roughly constant current despite
  changes in voltage. This is a simple way to get an approximately constant
  load current despite the sagging voltage as the battery discharges.
 
  I've used car headlights (about 4 amps each) and taillights (about 1 amp
  each) as load resistors for 12v battery testing.
 
   A simple QBasic program on an old laptop controlled the relay for
  the load and another for the charger via the parallel port.
  An E-meter with the RS232 comms option provided voltage, current,
  etc. measurements to the QBasic program.
 
 
  This describes the most common load tester I use. I have a few E-Meters /
  Link 10 / ProLink meters (all the same meter, but sold respectively by
  Cruising 

Re: [EVDL] Q about using an electronic load.

2014-11-07 Thread Lee Hart via EV

Peter Gabrielsson via EV wrote:

One relatively cheap way of doing high power cycle testing is to cycle
power between a large battery bank and the test battery using a
bidirectional DCDC converter.

The DCDC is simple since it's just a switching pole with an inductor and
some controls. A DC motor controller with regen capability can be used as
the DCDC converter, the controls should have a constant torque (current)
mode for it to be useful.


I've tried this. A motor controller has a significant amount of input 
ripple current, and a *huge* amount of output ripple current. You have 
to add inductors on the input and output to approximate DC. Since motor 
controllers handle high currents and switch at relatively low 
frequencies, these inductors are *big*.


What I used instead were Vicor modules. They switch at high frequencies, 
so the input and output filters are far smaller. Their internal filters 
are already adequate for battery testing. The output voltage and current 
can be adjusted with their TRIM pin. The output voltage can be higher or 
lower than the input voltage; important if you're ping-ponging power 
between two same-voltage batteries. For example, a VI-202 has a nominal 
12vdc input (10-20v), nominal 15v output (adjustable 7.5-16.5v), and 6.7 
amp max current. When I got mine, the VI-202 was $158 direct from Vicor.


Vicors are built to operate in parallel, so you can use as many as 
needed for high power. PS: I just checked eBay and see that someone has 
VI-202 modules for $99 each or 15 for $479 if anyone is interested. I 
have no connection with the seller.


The DC/DC doesn't have to be bidirectional; it's much easier to simply 
include a reversing relay that swaps input and output.

--
A designer knows he has achieved perfection not when there is
nothing left to add, but when there is nothing left to take away.
-- Antoine de Saint Exupery
--
Lee Hart's EV projects are at http://www.sunrise-ev.com/LeesEVs.htm
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Re: [EVDL] Q about using an electronic load.

2014-11-07 Thread Roger Stockton via EV
Michael Ross wrote:

 I think I need to be a notch or two above garage testing.  To provide
 results worth referencing.  I do have to be frugal and not spend where
 good things can be fabricated.  We want to be cost effective for clients
 that aren't at the million$ a year in sales level.

Thanks for clarifying that this is NOT a personal project, but a commercial one.

I think you will find that if you are doing testing for hire, that there is 
significant value in the credibility that comes with using professional grade 
commercial equipment versus explaining to the client that the coat hanger in 
that garbage can full of water really is a sensible piece of equipment for the 
test they are paying you to execute ;^

The cost effectiveness for smaller clients comes from *you* bearing the 
multi-$1000 investment in a proper active load and data acquisition and control 
equipment and possibly power supplies (for charging), and then recovering the 
cost over multiple clients and over time so that they have access to this level 
of test capability, when needed, for a much smaller up-front or per-instance 
expenditure.

If you are able to consider sufficiently large electronic loads, then ones that 
can push the energy back into the grid rather than dissipating it as heat 
become an option.  This capability doesn’t really become available until you 
are looking at loads of at least 6kW, and you should check with your local 
utility to see what sort of barriers will face you in trying to connect such a 
load before buying.

 I have a pretty comprehensive data acquisition system, National
 Instruments cRIO controller, 32, 5V biderectional DIO channels, 8 channels
 of high speed 5V bidirectional DIO, 16 channels of 24V DO, 8 channels of
 analog  input.  I have a couple 6 1/2 digit DMMs and 3  20 channel cards
 to use in them (slow but accurate).  All that can be programmed with some
 sophistication using LabVIEW.

Great!  For battery testing you generally don't need particularly fast scan 
speeds.  I'm not sure just what your 6.5-digit DMMs are, but they sound similar 
to the Agilent units I use for battery testing.  It is particularly nice that 
they can directly measure pack and cell voltages as well as shunts and 
thermocouples for monitoring temperature.  As long as the number of channels 
you are scanning isn't too great, it is possible to get at least a few readings 
per second in the uncommon event that your test requires it.  More typically, 
recording data at 1-10 second intervals is plenty fast for battery cycle 
testing.

 I won't need PLCs.

Also great, though I referred to use of a *PC*, same as you will use to run 
your LabVIEW application to control things ;^

 For cell testing I have an EMS 7.5V 300A 1700W supply.  I have not really
 used it, so I don't know exactly how to control it automatically.  It
 could do cell modules, but not packs.
 
 Then I have a couple of transformers in Lestronic II PbSO4 chargers 24V
 25Amp, and 36V 30A.  And I have a 480V:120V 7.5KVA transformer that ought
 to be useful somehow.

The power supply sounds like it could be useful, especially if equipped with 
IEEE-488 and if a LabVIEW driver is available for it.  The transformers sound 
less promising, at least for this purpose.

Really, it comes down to the sort of clientele you will serve and what sort of 
testing they require.  They may want you to test specific cells/modules, either 
recharging them using a provided charger or using your programmable supply to 
implement some specified charge regimen.
 
You may need to consider investing in water baths to maintain consistent 
temperatures throughout the test pack, and/or an environmental chamber to allow 
testing at elevated or reduced temperatures.  If you are going to test Li 
chemistries, especially at high rates and/or elevated temperatures, investigate 
the safety requirements for appropriate fire suppression and ventilation, etc.  
If you will be testing flooded lead acid, investigate the spill containment and 
personal safety requirements (eye wash, emergency shower, etc.), as well as 
hydrogen sensing equipment and ventilation requirements.

A properly equipped (inert gas purge, explosion proof locking door, suitable 
pressure relief fearture, possibly reinforced to handle the weight of larger 
(especially lead-acid) packs, etc.) environmental chamber runs about $60K, so 
once again part of the value provided for smaller clients is the ability for 
them to avoid the need to make this sort of investment in test equipment.

 I think I also want some reference standards.  But, I
 might make them, or settle for the calibrated DMMs.

The route you choose may depend on what you already do for other equipment in 
your lab, however, the approach we've taken is to maintain the calibration on 
the DMM/data acquisition units and rely on them to control the loads and power 
supplies so that the loads and power supplies themselves don't need to be kept 
calibrated.


Re: [EVDL] Q about using an electronic load.

2014-11-07 Thread John Lussmyer via EV
On Fri Nov 07 16:07:19 PST 2014 ev@lists.evdl.org said:
If you are able to consider sufficiently large electronic loads, then ones 
that can push the energy back into the grid rather than dissipating it as heat 
become an option.  This capability doesn?t really become available until you 
are looking at loads of at least 6kW, and you should check with your local 
utility to see what sort of barriers will face you in trying to connect such a 
load before buying.

Well, there are grid-tie inverters down as small as 200W or so readily 
available, often down to 12v input.


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Re: [EVDL] Q about using an electronic load.

2014-11-07 Thread Roger Stockton via EV
John Lussmyer wrote:

 If you are able to consider sufficiently large electronic loads, then
 ones that can push the energy back into the grid rather than dissipating
 it as heat become an option.  This capability doesn?t really become
 available until you are looking at loads of at least 6kW, and you should
 check with your local utility to see what sort of barriers will face you
 in trying to connect such a load before buying.
 
 Well, there are grid-tie inverters down as small as 200W or so readily
 available, often down to 12v input.

And these can certainly be a viable option, IF the batteries you are testing 
are compatible with the (typically) narrow input range of such inverters.  If 
you need to be able to test battery packs of arbitrary voltage and perhaps 
discharge to unusual (at least for typical lead-acid packs) end-of-discharge 
voltages, then off-the-shelf inverters may not be viable.

Cheers,

Roger.
 
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Re: [EVDL] Q about using an electronic load.

2014-11-07 Thread Michael Ross via EV
Hi Roger,

Just to clarify...this is not a personal project (though I do take it
personally), but it is also not commercial - in the profit taking sense.

The NC Clean Energy Technology Center is a not for profit (in fact the lab
barely survives on fee for service work, grants, and some small state
funding).  We are a non-academic Center that is part of the land grant
North Carolina State University, in Raleigh NC.  We don't do research, but
we find ways to provide hands on experience for interested engineering
students.

Presently, I am trying to learn what non-automotive EV manufacturers lack
in the way of testing, and other supplier management activities.  The ideas
range from regular - testing of cells packs, etc.; to unusual; for example,
we have a lot of Mandarin speaking students, who might be useful
communicating with Chinese manufacturers about technical issues.  We might
do postmortems and forensic evaluations of failed units.  We might test and
report on BMS and charger function.  And of course evaluate batteries and
packs.  I wonder if I should be looking at lead acid batteries also.  There
is a presumption that lithium and the next big thing will supplant lead
acid, but it might take a while. We need to serve that sector, too, if it
makes sense.

I am setting up a survey to collect bounds of the testing, and ideas of
other activities where we might be useful.  I will make it available to the
EVDL list and hope some for you will contribute to it.

Your messages have been very helpful, I am grateful.

Best regards,

Mike Ross

On Fri, Nov 7, 2014 at 7:07 PM, Roger Stockton via EV ev@lists.evdl.org
wrote:

 Michael Ross wrote:

  I think I need to be a notch or two above garage testing.  To provide
  results worth referencing.  I do have to be frugal and not spend where
  good things can be fabricated.  We want to be cost effective for clients
  that aren't at the million$ a year in sales level.

 Thanks for clarifying that this is NOT a personal project, but a
 commercial one.

 I think you will find that if you are doing testing for hire, that there
 is significant value in the credibility that comes with using professional
 grade commercial equipment versus explaining to the client that the coat
 hanger in that garbage can full of water really is a sensible piece of
 equipment for the test they are paying you to execute ;^

 The cost effectiveness for smaller clients comes from *you* bearing the
 multi-$1000 investment in a proper active load and data acquisition and
 control equipment and possibly power supplies (for charging), and then
 recovering the cost over multiple clients and over time so that they have
 access to this level of test capability, when needed, for a much smaller
 up-front or per-instance expenditure.

 If you are able to consider sufficiently large electronic loads, then ones
 that can push the energy back into the grid rather than dissipating it as
 heat become an option.  This capability doesn’t really become available
 until you are looking at loads of at least 6kW, and you should check with
 your local utility to see what sort of barriers will face you in trying to
 connect such a load before buying.

  I have a pretty comprehensive data acquisition system, National
  Instruments cRIO controller, 32, 5V biderectional DIO channels, 8
 channels
  of high speed 5V bidirectional DIO, 16 channels of 24V DO, 8 channels of
  analog  input.  I have a couple 6 1/2 digit DMMs and 3  20 channel cards
  to use in them (slow but accurate).  All that can be programmed with some
  sophistication using LabVIEW.

 Great!  For battery testing you generally don't need particularly fast
 scan speeds.  I'm not sure just what your 6.5-digit DMMs are, but they
 sound similar to the Agilent units I use for battery testing.  It is
 particularly nice that they can directly measure pack and cell voltages as
 well as shunts and thermocouples for monitoring temperature.  As long as
 the number of channels you are scanning isn't too great, it is possible to
 get at least a few readings per second in the uncommon event that your test
 requires it.  More typically, recording data at 1-10 second intervals is
 plenty fast for battery cycle testing.

  I won't need PLCs.

 Also great, though I referred to use of a *PC*, same as you will use to
 run your LabVIEW application to control things ;^

  For cell testing I have an EMS 7.5V 300A 1700W supply.  I have not really
  used it, so I don't know exactly how to control it automatically.  It
  could do cell modules, but not packs.
 
  Then I have a couple of transformers in Lestronic II PbSO4 chargers 24V
  25Amp, and 36V 30A.  And I have a 480V:120V 7.5KVA transformer that ought
  to be useful somehow.

 The power supply sounds like it could be useful, especially if equipped
 with IEEE-488 and if a LabVIEW driver is available for it.  The
 transformers sound less promising, at least for this purpose.

 Really, it comes down to the sort of clientele you 

Re: [EVDL] Q about using an electronic load.

2014-11-06 Thread Roger Stockton via EV
Michael Ross wrote:

 If I have a programmable electronic load, rather than purely resistive
 loads, is this an unrealistic way to discharge batteries?
 
 I gather they use power MOSFETS and switch them to product the desired
 output current from the batteries.  I think this implies some transients
 at some frequency.

A programmable load is fine for discharging batteries.

I believe the power devices are operated in linear mode, not PWMed, and have 
not observed any transients on the load current on any of the electronic loads 
I've used.

Cheers,

Roger.

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Re: [EVDL] Q about using an electronic load.

2014-11-06 Thread Cor van de Water via EV
Correct - a *supply* can use switching to minimize losses,
a *load* simply burns the power away in linear mode (current control).

Cor van de Water
Chief Scientist
Proxim Wireless Corporation http://www.proxim.com
Email: cwa...@proxim.com Private: http://www.cvandewater.info
Skype: cor_van_de_water Tel: +1 408 383 7626


-Original Message-
From: EV [mailto:ev-boun...@lists.evdl.org] On Behalf Of Roger Stockton
via EV
Sent: Thursday, November 06, 2014 1:12 PM
To: Electric Vehicle Discussion List
Subject: Re: [EVDL] Q about using an electronic load.

Michael Ross wrote:

 If I have a programmable electronic load, rather than purely resistive
 loads, is this an unrealistic way to discharge batteries?
 
 I gather they use power MOSFETS and switch them to product the desired
 output current from the batteries.  I think this implies some
transients
 at some frequency.

A programmable load is fine for discharging batteries.

I believe the power devices are operated in linear mode, not PWMed, and
have not observed any transients on the load current on any of the
electronic loads I've used.

Cheers,

Roger.

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Re: [EVDL] Q about using an electronic load.

2014-11-06 Thread Michael Ross via EV
I have heard of putting a roll of fencing in a tank to steam off heat.  Is
this useful with a programmable load?  Or is this just a crude way to
discharge.

Someone mentioned needing a heat dispensing means would be needed with a
programmable load.

Any recommendation of actual units to look at?

On Thu, Nov 6, 2014 at 4:55 PM, Cor van de Water via EV ev@lists.evdl.org
wrote:

 Correct - a *supply* can use switching to minimize losses,
 a *load* simply burns the power away in linear mode (current control).

 Cor van de Water
 Chief Scientist
 Proxim Wireless Corporation http://www.proxim.com
 Email: cwa...@proxim.com Private: http://www.cvandewater.info
 Skype: cor_van_de_water Tel: +1 408 383 7626


 -Original Message-
 From: EV [mailto:ev-boun...@lists.evdl.org] On Behalf Of Roger Stockton
 via EV
 Sent: Thursday, November 06, 2014 1:12 PM
 To: Electric Vehicle Discussion List
 Subject: Re: [EVDL] Q about using an electronic load.

 Michael Ross wrote:

  If I have a programmable electronic load, rather than purely resistive
  loads, is this an unrealistic way to discharge batteries?
 
  I gather they use power MOSFETS and switch them to product the desired
  output current from the batteries.  I think this implies some
 transients
  at some frequency.

 A programmable load is fine for discharging batteries.

 I believe the power devices are operated in linear mode, not PWMed, and
 have not observed any transients on the load current on any of the
 electronic loads I've used.

 Cheers,

 Roger.

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-- 
Put this question to yourself: should I use everyone else to attain
happiness, or should I help others gain happiness?
*Dalai Lama *

Tell me what it is you plan to do
With your one wild and precious life?
Mary Oliver, The summer day.

To invent, you need a good imagination and a pile of junk.
Thomas A. Edison
http://www.brainyquote.com/quotes/quotes/t/thomasaed125362.html

A public-opinion poll is no substitute for thought.
*Warren Buffet*

Michael E. Ross
(919) 550-2430 Land
(919) 576-0824 https://www.google.com/voice/b/0?pli=1#phones Google Phone
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(919) 513-0418 Desk

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Re: [EVDL] Q about using an electronic load.

2014-11-06 Thread Cor van de Water via EV
No, a programmable load will typically have built-in load, but there may
be units that only are a controller

and expect a bank of resistors or the like externally.

For doing it on the cheap, you can take a length of wire that can
dissipate the heat, either by spreading it out

(I once did several cycles of testing on a 12V 110Ah battery using about
200 ft of copper wire strung around

my garage on two parallel strings, so I got about 80A of discharge
current).

You can also build a dissipative load relatively easy with power MOSFETs
on a heatsink, a shunt resistor

to measure the current, an opamp to compare the desired current to the
set value and drive the MOSFETs

and a small 12V power supply to power the thing.

Add a second opamp to measure voltage and stop the discharge at a set
voltage and you are pretty far

along in having your own programmable load. Add a meter or two and some
indicators and you are in business.

 

Cor van de Water
Chief Scientist
Proxim Wireless Corporation http://www.proxim.com
http://www.proxim.com 
Email: cwa...@proxim.com Private: http://www.cvandewater.info
http://www.cvandewater.infom 
Skype: cor_van_de_water Tel: +1 408 383 7626



From: Michael Ross [mailto:michael.e.r...@gmail.com] 
Sent: Thursday, November 06, 2014 2:25 PM
To: Cor van de Water; Electric Vehicle Discussion List
Subject: Re: [EVDL] Q about using an electronic load.

 

I have heard of putting a roll of fencing in a tank to steam off heat.
Is this useful with a programmable load?  Or is this just a crude way to
discharge.  

 

Someone mentioned needing a heat dispensing means would be needed with a
programmable load.  

 

Any recommendation of actual units to look at?

 

On Thu, Nov 6, 2014 at 4:55 PM, Cor van de Water via EV
ev@lists.evdl.org wrote:

Correct - a *supply* can use switching to minimize losses,
a *load* simply burns the power away in linear mode (current control).

Cor van de Water
Chief Scientist
Proxim Wireless Corporation http://www.proxim.com
Email: cwa...@proxim.com Private: http://www.cvandewater.info
Skype: cor_van_de_water Tel: +1 408 383 7626
tel:%2B1%20408%20383%207626 



-Original Message-
From: EV [mailto:ev-boun...@lists.evdl.org] On Behalf Of Roger Stockton
via EV
Sent: Thursday, November 06, 2014 1:12 PM
To: Electric Vehicle Discussion List
Subject: Re: [EVDL] Q about using an electronic load.

Michael Ross wrote:

 If I have a programmable electronic load, rather than purely resistive
 loads, is this an unrealistic way to discharge batteries?

 I gather they use power MOSFETS and switch them to product the desired
 output current from the batteries.  I think this implies some
transients
 at some frequency.

A programmable load is fine for discharging batteries.

I believe the power devices are operated in linear mode, not PWMed, and
have not observed any transients on the load current on any of the
electronic loads I've used.

Cheers,

Roger.

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-- 

Put this question to yourself: should I use everyone else to attain
happiness, or should I help others gain happiness?  

Dalai Lama 

 

Tell me what it is you plan to do

With your one wild and precious life?

Mary Oliver, The summer day.

 

To invent, you need a good imagination and a pile of junk.

Thomas A. Edison
http://www.brainyquote.com/quotes/quotes/t/thomasaed125362.html 

 

A public-opinion poll is no substitute for thought.

Warren Buffet

 

Michael E. Ross

(919) 550-2430 Land

(919) 576-0824 https://www.google.com/voice/b/0?pli=1#phones  Google
Phone

(919) 631-1451 Cell
(919) 513-0418 Desk

michael.e.r...@gmail.com

mailto:michael.e.r...@gmail.com 



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Re: [EVDL] Q about using an electronic load.

2014-11-06 Thread Lee Hart via EV

Roger Stockton via EV wrote:

A programmable load is fine for discharging batteries.

I believe the power devices are operated in linear mode, not PWMed, and have 
not observed any transients on the load current on any of the electronic loads 
I've used.


I agree. The programmable loads I've seen and used are all linear. Using 
PWM (without a massive filter to make it look like DC) would give you 
bad data, and invalidate the results.


By nature, the load is going to convert electricity into heat. If you're 
handling big power, a *lot* of heat. This creates an incentive for 
regenerative loads (using the power to run a motor, or push it back into 
the AC line, etc.) Some of the really big programmable loads do this. AC 
Propulsion has one rated at 100kw that does this.


A battery charger can be a particularly handy load. I've ping-ponged 
the power between two batteries to test them both, discharging #1 to 
charge #2, and then when #1 is dead, flip it around and use #2 to charge 
#1 etc. This way, most of the energy is recycled, and you only need a 
small extra charger to make up the losses. I used Vicor modules for 
this, whose input and output are essentially DC.


--
A designer knows he has achieved perfection not when there is
nothing left to add, but when there is nothing left to take away.
-- Antoine de Saint Exupery
--
Lee Hart's EV projects are at http://www.sunrise-ev.com/LeesEVs.htm
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Re: [EVDL] Q about using an electronic load.

2014-11-06 Thread Lee Hart via EV

Michael Ross via EV wrote:

I have heard of putting a roll of fencing in a tank to steam off heat.  Is
this useful with a programmable load?  Or is this just a crude way to
discharge.


This is just a quick-n-dirty way to make a big, high-power, cheap resistor.

 Any recommendation of actual units to look at?

What power level (volts and amps) are you looking at?

--
A designer knows he has achieved perfection not when there is
nothing left to add, but when there is nothing left to take away.
-- Antoine de Saint Exupery
--
Lee Hart's EV projects are at http://www.sunrise-ev.com/LeesEVs.htm
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Re: [EVDL] Q about using an electronic load.

2014-11-06 Thread Michael Ross via EV
Thank you Cor.  I am cash strapped so this sort of DIY advice is very
helpful.

Mike

On Thu, Nov 6, 2014 at 5:33 PM, Cor van de Water via EV ev@lists.evdl.org
wrote:

 No, a programmable load will typically have built-in load, but there may
 be units that only are a controller

 and expect a bank of resistors or the like externally.

 For doing it on the cheap, you can take a length of wire that can
 dissipate the heat, either by spreading it out

 (I once did several cycles of testing on a 12V 110Ah battery using about
 200 ft of copper wire strung around

 my garage on two parallel strings, so I got about 80A of discharge
 current).

 You can also build a dissipative load relatively easy with power MOSFETs
 on a heatsink, a shunt resistor

 to measure the current, an opamp to compare the desired current to the
 set value and drive the MOSFETs

 and a small 12V power supply to power the thing.

 Add a second opamp to measure voltage and stop the discharge at a set
 voltage and you are pretty far

 along in having your own programmable load. Add a meter or two and some
 indicators and you are in business.



 Cor van de Water
 Chief Scientist
 Proxim Wireless Corporation http://www.proxim.com
 http://www.proxim.com
 Email: cwa...@proxim.com Private: http://www.cvandewater.info
 http://www.cvandewater.infom
 Skype: cor_van_de_water Tel: +1 408 383 7626

 

 From: Michael Ross [mailto:michael.e.r...@gmail.com]
 Sent: Thursday, November 06, 2014 2:25 PM
 To: Cor van de Water; Electric Vehicle Discussion List
 Subject: Re: [EVDL] Q about using an electronic load.



 I have heard of putting a roll of fencing in a tank to steam off heat.
 Is this useful with a programmable load?  Or is this just a crude way to
 discharge.



 Someone mentioned needing a heat dispensing means would be needed with a
 programmable load.



 Any recommendation of actual units to look at?



 On Thu, Nov 6, 2014 at 4:55 PM, Cor van de Water via EV
 ev@lists.evdl.org wrote:

 Correct - a *supply* can use switching to minimize losses,
 a *load* simply burns the power away in linear mode (current control).

 Cor van de Water
 Chief Scientist
 Proxim Wireless Corporation http://www.proxim.com
 Email: cwa...@proxim.com Private: http://www.cvandewater.info
 Skype: cor_van_de_water Tel: +1 408 383 7626
 tel:%2B1%20408%20383%207626



 -Original Message-
 From: EV [mailto:ev-boun...@lists.evdl.org] On Behalf Of Roger Stockton
 via EV
 Sent: Thursday, November 06, 2014 1:12 PM
 To: Electric Vehicle Discussion List
 Subject: Re: [EVDL] Q about using an electronic load.

 Michael Ross wrote:

  If I have a programmable electronic load, rather than purely resistive
  loads, is this an unrealistic way to discharge batteries?
 
  I gather they use power MOSFETS and switch them to product the desired
  output current from the batteries.  I think this implies some
 transients
  at some frequency.

 A programmable load is fine for discharging batteries.

 I believe the power devices are operated in linear mode, not PWMed, and
 have not observed any transients on the load current on any of the
 electronic loads I've used.

 Cheers,

 Roger.

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 --

 Put this question to yourself: should I use everyone else to attain
 happiness, or should I help others gain happiness?

 Dalai Lama



 Tell me what it is you plan to do

 With your one wild and precious life?

 Mary Oliver, The summer day.



 To invent, you need a good imagination and a pile of junk.

 Thomas A. Edison
 http://www.brainyquote.com/quotes/quotes/t/thomasaed125362.html



 A public-opinion poll is no substitute for thought.

 Warren Buffet



 Michael E. Ross

 (919) 550-2430 Land

 (919) 576-0824 https://www.google.com/voice/b/0?pli=1#phones  Google
 Phone

 (919) 631-1451 Cell
 (919) 513-0418 Desk

 michael.e.r...@gmail.com

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-- 
Put this question to yourself: should I use everyone else to attain
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*Dalai Lama *

Tell me what it is you plan to do
With your one wild

Re: [EVDL] Q about using an electronic load.

2014-11-06 Thread Paul Dove via EV
I have always used a load bank. It works great

Sent from my iPhone

 On Nov 6, 2014, at 2:18 PM, Michael Ross via EV ev@lists.evdl.org wrote:
 
 I am investigating how to test cells and packs - I will need to charge and
 discharge.
 
 If I have a programmable electronic load, rather than purely resistive
 loads, is this an unrealistic way to discharge batteries?
 
 I gather they use power MOSFETS and switch them to product the desired
 output current from the batteries.  I think this implies some transients at
 some frequency.
 
 Does it matter?
 
 Can I mitigate the effect with lots of capacitors?
 
 Or whatever else I have not thought of...
 
 (Please bear with me going forward, I have a lot of questions in the same
 vein.)
 
 
 Thanks,
 
 -- 
 *Michael Ross*
 
 *Testing Laboratory Manager*
 *NC Clean Energy Technology Center*
 *Testing Laboratory*
 *NC State University*
 919.513.0418 (office)
 919.576.0824 (alternate)
 919.631.1451 (cell)
 michael_r...@ncsu.edu
 
 www.nccleantech.ncsu.edu
 Formerly the NC Solar Center
 
 *JOIN THE CONVERSATION ONLINE*
 Facebook http://facebook.com/NCSolarCenter / Twitter
 https://twitter.com/search?q=nccleantech / LinkedIn
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Re: [EVDL] Q about using an electronic load.

2014-11-06 Thread Paul Dove via EV
I have an HP 6050a 1800 watt electronic load

Sent from my iPhone

 On Nov 6, 2014, at 4:25 PM, Michael Ross via EV ev@lists.evdl.org wrote:
 
 I have heard of putting a roll of fencing in a tank to steam off heat.  Is
 this useful with a programmable load?  Or is this just a crude way to
 discharge.
 
 Someone mentioned needing a heat dispensing means would be needed with a
 programmable load.
 
 Any recommendation of actual units to look at?
 
 On Thu, Nov 6, 2014 at 4:55 PM, Cor van de Water via EV ev@lists.evdl.org
 wrote:
 
 Correct - a *supply* can use switching to minimize losses,
 a *load* simply burns the power away in linear mode (current control).
 
 Cor van de Water
 Chief Scientist
 Proxim Wireless Corporation http://www.proxim.com
 Email: cwa...@proxim.com Private: http://www.cvandewater.info
 Skype: cor_van_de_water Tel: +1 408 383 7626
 
 
 -Original Message-
 From: EV [mailto:ev-boun...@lists.evdl.org] On Behalf Of Roger Stockton
 via EV
 Sent: Thursday, November 06, 2014 1:12 PM
 To: Electric Vehicle Discussion List
 Subject: Re: [EVDL] Q about using an electronic load.
 
 Michael Ross wrote:
 
 If I have a programmable electronic load, rather than purely resistive
 loads, is this an unrealistic way to discharge batteries?
 
 I gather they use power MOSFETS and switch them to product the desired
 output current from the batteries.  I think this implies some
 transients
 at some frequency.
 
 A programmable load is fine for discharging batteries.
 
 I believe the power devices are operated in linear mode, not PWMed, and
 have not observed any transients on the load current on any of the
 electronic loads I've used.
 
 Cheers,
 
 Roger.
 
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 -- 
 Put this question to yourself: should I use everyone else to attain
 happiness, or should I help others gain happiness?
 *Dalai Lama *
 
 Tell me what it is you plan to do
 With your one wild and precious life?
 Mary Oliver, The summer day.
 
 To invent, you need a good imagination and a pile of junk.
 Thomas A. Edison
 http://www.brainyquote.com/quotes/quotes/t/thomasaed125362.html
 
 A public-opinion poll is no substitute for thought.
 *Warren Buffet*
 
 Michael E. Ross
 (919) 550-2430 Land
 (919) 576-0824 https://www.google.com/voice/b/0?pli=1#phones Google Phone
 (919) 631-1451 Cell
 (919) 513-0418 Desk
 
 michael.e.r...@gmail.com
 michael.e.r...@gmail.com
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Re: [EVDL] Q about using an electronic load.

2014-11-06 Thread EVDL Administrator via EV
My dummy load is the resistive heat strips from a couple of derelict heat 
pumps.  Since I use them at 144v rather than 240v, I split each in the 
middle.  With all 4 (mismatched) half-elements in parallel, it uses about 
100 amps at 144 volts, exactly what I was looking for.  It also heats up the 
garage rather nicely when I'm tinkering on a cool day.

To sub for the heat pumps' air plenums, I put the elements in an old metal 
mailbox that had lost its door.  I cut a hole in the back and added a fan 
from a scrapped range hood (runs on 117vac).  I switch it to the test 
battery with an extra contactor I had lying about.  I meant to add a 12v 
power puck to pull in the contactor when I switched on the fan, but never 
did, so I have to power the contactor with a 12v battery.  Fortunately I 
have a few taking up space in the garage.

I admit, it looks pretty laughable, but it's all free / recycled materials, 
and it works.  The only problem is that the fan is gunky from years of 
cooking grease, so it takes a couple of minutes to really get going when I 
power it up.

To vary the current, I suppose you could add a PWM DC controller to 
something like this.  You might have to add some series inductance unless 
you were sure that you'd never need to hit controller's current limit (that 
is, the load was such that it would never exceed the controller's current 
capacity).

David Roden - Akron, Ohio, USA
EVDL Administrator

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Re: [EVDL] Q about using an electronic load.

2014-11-06 Thread Roger Stockton via EV
Michael Ross wrote:

 I have heard of putting a roll of fencing in a tank to steam off heat.  Is
 this useful with a programmable load?  Or is this just a crude way to
 discharge.

Probably not, unless the electronic load you choose is designed to be used with 
an external load bank, or you plan to control the electronic load from a remote 
source rather than simply setting it to regulate the desired load current on 
its own.

An external load bank (coat hanger or other wire in a bucket of water or 
fan-cooled power resistors, etc.) can be useful if you want to increase the 
power capability of your electronic load (or conversely, to be able to use a 
smaller - and cheaper - electronic load than you could otherwise).

For instance, when testing a 12V battery you will typically discharge to about 
10V minimum; if your desired discharge rate is 75A, then your minimum load is 
about 750W.  If you want to be sure that you can pull the full 75A from a 
freshly charged battery, it needs to be able to handle the maximum load of 
about 15V x 75A = 1125W.  If you use a resistive load to handle most of the 
minimum load requirement, then your electronic load only needs to be sized to 
handle the difference (in this case 1125-750 = 375W) instead of the full amount.

 Someone mentioned needing a heat dispensing means would be needed with a
 programmable load.

Not unless you pick up a water-cooled load.  The air-cooled loads have built in 
fans and will cool themselves.  If you are discharging a large capacity battery 
in a small room, you may need to open a window or otherwise allow for some 
ventilation as the room will warm up.

 Any recommendation of actual units to look at?

I've mostly used DLP- and RBL-series units from TDI (Transistor Devices).  They 
are often available used, and are generally basic rugged units.  You don't need 
particularly fancy features for battery discharging as most often you will use 
the load in constant current or possibly constant power.  In constant current 
mode, the TDI loads can have the load current controlled remotely by a 0-5V 
signal, so you can use an external means to monitor the total load current 
drawn by the electronic load and a resistive load and then control the 
electronic load to regulate the total current at the desired level.  They also 
can be enabled/disabled remotely with a simple relay or opto so that your data 
logger can turn the load off when the battery voltage reaches the desired 
end-of-discharge voltage.  Some models support IEEE-488 (GPIB) communication, 
in which case you can achieve all of this controllability through software 
control, provided you spring for a GPIB interface for your PC.

I've also used loads from NH Research (NHR, this is what I have at home) and 
Chroma.

This site provides an idea of what sort of devices are available on the used 
market:

http://www.alltest.net/s.nl/sc.2/category.16/.f

Cheers,

Roger.

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Re: [EVDL] Q about using an electronic load.

2014-11-06 Thread Michael Ross via EV
Excellent, Roger, Thank you.

On Thu, Nov 6, 2014 at 7:08 PM, Roger Stockton via EV ev@lists.evdl.org
wrote:

 Michael Ross wrote:

  I have heard of putting a roll of fencing in a tank to steam off heat.
 Is
  this useful with a programmable load?  Or is this just a crude way to
  discharge.

 Probably not, unless the electronic load you choose is designed to be used
 with an external load bank, or you plan to control the electronic load from
 a remote source rather than simply setting it to regulate the desired load
 current on its own.

 An external load bank (coat hanger or other wire in a bucket of water or
 fan-cooled power resistors, etc.) can be useful if you want to increase the
 power capability of your electronic load (or conversely, to be able to use
 a smaller - and cheaper - electronic load than you could otherwise).

 For instance, when testing a 12V battery you will typically discharge to
 about 10V minimum; if your desired discharge rate is 75A, then your minimum
 load is about 750W.  If you want to be sure that you can pull the full 75A
 from a freshly charged battery, it needs to be able to handle the maximum
 load of about 15V x 75A = 1125W.  If you use a resistive load to handle
 most of the minimum load requirement, then your electronic load only needs
 to be sized to handle the difference (in this case 1125-750 = 375W) instead
 of the full amount.

  Someone mentioned needing a heat dispensing means would be needed with a
  programmable load.

 Not unless you pick up a water-cooled load.  The air-cooled loads have
 built in fans and will cool themselves.  If you are discharging a large
 capacity battery in a small room, you may need to open a window or
 otherwise allow for some ventilation as the room will warm up.

  Any recommendation of actual units to look at?

 I've mostly used DLP- and RBL-series units from TDI (Transistor Devices).
 They are often available used, and are generally basic rugged units.  You
 don't need particularly fancy features for battery discharging as most
 often you will use the load in constant current or possibly constant
 power.  In constant current mode, the TDI loads can have the load current
 controlled remotely by a 0-5V signal, so you can use an external means to
 monitor the total load current drawn by the electronic load and a resistive
 load and then control the electronic load to regulate the total current at
 the desired level.  They also can be enabled/disabled remotely with a
 simple relay or opto so that your data logger can turn the load off when
 the battery voltage reaches the desired end-of-discharge voltage.  Some
 models support IEEE-488 (GPIB) communication, in which case you can achieve
 all of this controllability through software control, provided you spring
 for a GPIB interface for your PC.

 I've also used loads from NH Research (NHR, this is what I have at home)
 and Chroma.

 This site provides an idea of what sort of devices are available on the
 used market:

 http://www.alltest.net/s.nl/sc.2/category.16/.f

 Cheers,

 Roger.

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-- 
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happiness, or should I help others gain happiness?
*Dalai Lama *

Tell me what it is you plan to do
With your one wild and precious life?
Mary Oliver, The summer day.

To invent, you need a good imagination and a pile of junk.
Thomas A. Edison
http://www.brainyquote.com/quotes/quotes/t/thomasaed125362.html

A public-opinion poll is no substitute for thought.
*Warren Buffet*

Michael E. Ross
(919) 550-2430 Land
(919) 576-0824 https://www.google.com/voice/b/0?pli=1#phones Google Phone
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Re: [EVDL] Q about using an electronic load.

2014-11-06 Thread Roger Stockton via EV
Michael Ross wrote:

 I am investigating how to test cells and packs - I will need to charge and
 discharge.
 
 If I have a programmable electronic load, rather than purely resistive
 loads, is this an unrealistic way to discharge batteries?

Thought I'd mention that while a programmable load is an *excellent* way to 
discharge when testing batteries, it can be pricey (typically about $2/W on the 
used market).  If you have a load bank, or need one for other reasons, then by 
all means use it.  If you are considering buying one just for this purpose, 
then carefully consider what other equipment you have or will need to acquire 
to go with it.

If you get a load large enough to handle your needs on its own (i.e. it can 
handle the desired discharge current even with a fully-charge battery), and you 
get one equipped with a communications interface (GPIB/IEEE-488 or RS232, 
typically), then you may be able to use its own voltage and current measurement 
capabilities to avoid the need to purchase a standalone data logger or USB 
DAC/digital I/O device to take measurements and control things.

If you already have a data logger or other means of measuring/controlling a 
load and charger, then perhaps consider using a passive load in parallel with a 
smaller electronic load, so that you can save money on the electronic load 
purchase.

Or, you may be able to go in entirely the opposite direction and use a 
completely passive load bank.  I started out with a battery cycler setup 
consisting of a bank of 12VDC Edison-base (household screw-type) light bulbs 
switched by a continuous duty Ford starter solenoid-type RV battery switch.  A 
simple QBasic program on an old laptop controlled the relay for the load and 
another for the charger via the parallel port.  An E-meter with the RS232 comms 
option provided voltage, current, etc. measurements to the QBasic program.

Incandescent bulbs have the nice property that the current they draw varies 
less with voltage than would a purely resistive load, so you can get a 
reasonably constant discharge current simply.  Unless your battery voltage is 
significantly below the rated voltage of the bulbs, they also provide a nice 
visual indication that they are on and hot. ;^

Cheers,

Roger.

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Re: [EVDL] Q about using an electronic load.

2014-11-06 Thread Michael Ross via EV
Hi Roger,

Thanks for the thoughtful reply.

I think I need to be a notch or two above garage testing.  To provide
results worth referencing.  I do have to be frugal and not spend where good
things can be fabricated.  We want to be cost effective for clients that
aren't at the million$ a year in sales level.  Large OEMs can care for
themselves.

Since we are a functioning test lab, I have an assortment of quality
measuring instruments - just not specific to battery testing.  We test
solar thermal collectors.  Lots of radiation, temperature, and flow
capability.

I have a pretty comprehensive data acquisition system, National Instruments
cRIO controller, 32, 5V biderectional DIO channels, 8 channels of high
speed 5V bidirectional DIO, 16 channels of 24V DO, 8 channels of analog
 input.  I have a couple 6 1/2 digit DMMs and 3  20 channel cards to use in
them (slow but accurate).  All that can be programmed with some
sophistication using LabVIEW.  I won't need PLCs.

With some relays and contactors, I can probably move on to the power
supplies and possibly load banks for a place to spend money.

For cell testing I have an EMS 7.5V 300A 1700W supply.  I have not really
used it, so I don't know exactly how to control it automatically.  It could
do cell modules, but not packs.

Then I have a couple of transformers in Lestronic II PbSO4 chargers 24V
25Amp, and 36V 30A.  And I have a 480V:120V 7.5KVA transformer that ought
to be useful somehow.

It is a start.

If I can get any funding at all, I think knowing the power and load needed
for the most probable testing, and getting good equipment to provide those
would be smart.  I think I also want some reference standards.  But, I
might make them, or settle for the calibrated DMMs.

Mike

On Thu, Nov 6, 2014 at 7:48 PM, Roger Stockton via EV ev@lists.evdl.org
wrote:

 Michael Ross wrote:

  I am investigating how to test cells and packs - I will need to charge
 and
  discharge.
 
  If I have a programmable electronic load, rather than purely resistive
  loads, is this an unrealistic way to discharge batteries?

 Thought I'd mention that while a programmable load is an *excellent* way
 to discharge when testing batteries, it can be pricey (typically about $2/W
 on the used market).  If you have a load bank, or need one for other
 reasons, then by all means use it.  If you are considering buying one just
 for this purpose, then carefully consider what other equipment you have or
 will need to acquire to go with it.

 If you get a load large enough to handle your needs on its own (i.e. it
 can handle the desired discharge current even with a fully-charge battery),
 and you get one equipped with a communications interface (GPIB/IEEE-488 or
 RS232, typically), then you may be able to use its own voltage and current
 measurement capabilities to avoid the need to purchase a standalone data
 logger or USB DAC/digital I/O device to take measurements and control
 things.

 If you already have a data logger or other means of measuring/controlling
 a load and charger, then perhaps consider using a passive load in parallel
 with a smaller electronic load, so that you can save money on the
 electronic load purchase.

 Or, you may be able to go in entirely the opposite direction and use a
 completely passive load bank.  I started out with a battery cycler setup
 consisting of a bank of 12VDC Edison-base (household screw-type) light
 bulbs switched by a continuous duty Ford starter solenoid-type RV battery
 switch.  A simple QBasic program on an old laptop controlled the relay for
 the load and another for the charger via the parallel port.  An E-meter
 with the RS232 comms option provided voltage, current, etc. measurements to
 the QBasic program.

 Incandescent bulbs have the nice property that the current they draw
 varies less with voltage than would a purely resistive load, so you can get
 a reasonably constant discharge current simply.  Unless your battery
 voltage is significantly below the rated voltage of the bulbs, they also
 provide a nice visual indication that they are on and hot. ;^

 Cheers,

 Roger.

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 http://groups.yahoo.com/group/NEDRA)




-- 
Put this question to yourself: should I use everyone else to attain
happiness, or should I help others gain happiness?
*Dalai Lama *

Tell me what it is you plan to do
With your one wild and precious life?
Mary Oliver, The summer day.

To invent, you need a good imagination and a pile of junk.
Thomas A. Edison
http://www.brainyquote.com/quotes/quotes/t/thomasaed125362.html

A public-opinion poll is no substitute for thought.
*Warren Buffet*

Michael E. Ross
(919) 550-2430 Land
(919) 576-0824 https://www.google.com/voice/b/0?pli=1#phones Google Phone
(919) 631-1451 Cell
(919) 513-0418 Desk

michael.e.r...@gmail.com