Re: [EVDL] Suitable Load?

[Lee Hart via EV]

Robert Bruninga via EV wrote:

spring-wound bathroom timer ... works fine for AC or DC ...15-20 amps.



Reminder:  But ONLY AT LOW VOLTAGE DC.  Use it once at any higher voltage
on DC, and when the contacts open, and arc will not only burn it up, but
probably catch it on fire.

Solution of course is to put a snubber resistor and capacitor across the
contacts.  But without that, it will not open a HVDC circuit,... just arc
and burn.


A good point! As a rule, an AC rated contact is good for about 1/4 the 
voltage on DC. Thus the 120vac/30vdc rating that's frequently seen. In 
the context mentioned in this thread (testing individual cells), the AC 
contact is fine because the DC voltage is well under 30v.


If you have to switch a *high* DC voltage, a snubber helps a lot, 
particularly with inductive loads. I described snubbers at 
http://www.sunrise-ev.com/LeesEVs.htm#snubbers. I also described some 
simple battery testers at http://www.sunrise-ev.com (about halfway down 
the page at "Lee's EVs". :-)


Or, use the AC-rated contact to switch a relay or contactor with 
contacts rated for the voltage and current you are actually switching.


--
Any intelligent fool can make things bigger, more complex, and more
violent. It takes a touch of genius, and a lot of courage, to move
in the opposite direction. -- Albert Einstein
--
Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com
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Re: [EVDL] Suitable Load?

[europeanfitn...@netzero.net via EV]

I'm Pascal LardyCould you help me  with the zener battery reg.  that are 
described inMinimalist Battery Regulators
by Lee Hart; modifications by Cor Van de Waterand I have a question  if you 
have time.I own an hybrid sailboat with 12 x 12 volt battery AGM bank.Superior 
Plates with an expected life span of 10 to 12 years in float service 
applications.
 Nominal Voltage20Hr CapacityCCA 
MCA
RC (min)
 Energy
(kWH)
 Terminal Posts DimensionsWeight 
Charging Current* 
Charging Voltage 
Float Voltage 
 12V155AH
790A 
1150A350 2.1SAE+3/8" STUD12.9"w x 6.9"d x 10"h/10.8th91lb 
10A-35A
14.4V-14.9V 
13.5V-13.8V 
* Warning: Do not use a wet battery constant current charger to recharge any 
VMAX battery.25A @ 1.75/Cell  350Min
 75A @ 1.75/Cell90Min Recommended Charging Options:Smart / Microprocessor 
controlled charger: Battery Charger Guide
Vehicle Alternator: 14V-15V.
RV Converter: 14V-15V.

Solar Panel: 225W-500W.
Wind Turbine: 225W-500W.

Charge Controller: 25A-UP
Operating Temperature Range:Discharge: -4~140F
Charge: 14~140F
Storage: -4~140F
Temperature Compensation:Cycle use: -30mV/C 

Standby use: -20mV/C 

I like to install zener regulator to make sure that each battery from that bank 
get the right voltage.Minimum voltage need to be 12.18max voltage need to be no 
more than 14.6 I like the Cor Van de Water design better because the life of a 
LED is much longer than a regular bulb, can you tell me  if what Zener diode I 
need?  2 of 6.8 V?see Parts List: (per battery) 2 - heavy duty copper 5/16" 
ring terminals, for 6 gauge wire (Waytek 36472)
2 - 6" lengths of #18 or so insulated wire
2 - 6.8v 5W zener diode, type 1N5342B1
1- 4 ohm, 2 Watt resistor; a 1- 56 ohm, and 1/8 watt resistor; and an one red 
LED.
Heat shrink tubing to fit the barrels of the terminals
Thermally conductive epoxy filler (available from electronics vendors) and also 
I need that the mini voltage too don't go bellow 12.18/v .Buy the ay I was 
trying to buy the kits but the link don't work and it's for flooded battery. 
Thanks Pascal


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 Additionally, homeowners who refinance from 30 year fixed mortgages to 15 year 

Re: [EVDL] Suitable Load?

[Lee Hart via EV]

Paul Dove via EV wrote:

Halogen bulbs are made in general for 6V, 12V, 24V... Using too low
a voltage will produce little current and too high a voltage will
produce high current and overheating of the filament


Actually, light bulbs don't behave like resistors. Ohm's law doesn't 
apply. :-)


A light bulb's apparent resistance changes drastically with temperature. 
The cold resistance (measured with an ohmmeter) is easily 1:10th that of 
its hot resistance (current divided by voltage at full rated voltage). 
Depending on the type of light, an 8-1 change in voltage only causes 
about a 2:1 change in current.


This means that light bulbs can be used as crude constant-current loads. 
The current only changes slightly despite large changes in voltage. This 
characteristic is ideal for testing batteries, where you'd like the 
current to stay the same despite changes in cell or battery voltage.

--
Any intelligent fool can make things bigger, more complex, and more
violent. It takes a touch of genius, and a lot of courage, to move
in the opposite direction. -- Albert Einstein
--
Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com
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Re: [EVDL] Suitable Load?

[Cor van de Water via EV]

Exactly, start by simply disconnecting one wire of the charger from the
pack and inserting a standard 60W 120V light bulb (must be an
incandescent bulb!)
and see if the charger will output its max voltage for long enough to
get the pack balanced. Typically a charger has a time cut-off, you may
need to switch your charger to an "equalization" type setting to allow
it to provide the max charge voltage for long enough while the bulb is
limiting the current and the regulators keep everything from reaching
max cutoff voltage, so that all low cells get charged with 1/2 Amp and
all high cells have the reg bypassing the current until *all* cells
start to bypass and that should be the moment that the BMS tells the
charger to quit.
It may be that you need to reset the charger several times to get it to
charge long enough at a low current to get everything balanced again,
and it may even be that the charger refuses to deliver max voltage and
turns off immediately. In that case, you need to make or borrow a high
voltage power supply (does not need to be a charger, just a fixed
voltage that is higher than the max pack voltage by several tens, up to
120V.
For example if your pack is 120V nominal and you have a power supply
that can generate 150V then this works well.
If you have no solution then I can help, I have dozens of 48v 1.5A power
supplies that look like a large laptop power supply. Put several of them
in series to multiply the output voltage and you can build your own
power supply for balancing a pack at any voltage. Is your pack 300V then
simply use 7 power supplies in series to get 336V from them and wire the
bulb in series to send about 1/2 Amp to your pack. Watch the BMS
regulate (bypass) the full cells and after a weekend of balancing, your
pack should have all the reg lights on that it has balanced it
completely.

But start with the simple solution to check if you can use the existing
charger and a light bulb.
Success!

Cor van de Water 
Chief Scientist 
Proxim Wireless 
  
office +1 408 383 7626Skype: cor_van_de_water 
XoIP   +31 87 784 1130private: cvandewater.info 

http://www.proxim.com

This email message (including any attachments) contains confidential and
proprietary information of Proxim Wireless Corporation.  If you received
this message in error, please delete it and notify the sender.  Any
unauthorized use, disclosure, distribution, or copying of any part of
this message is prohibited.


-Original Message-
From: EV [mailto:ev-boun...@lists.evdl.org] On Behalf Of Willie2 via EV
Sent: Thursday, November 05, 2015 7:01 AM
To: Robert Bruninga; Electric Vehicle Discussion List
Subject: Re: [EVDL] Suitable Load?

On 11/05/2015 07:44 AM, Robert Bruninga via EV wrote:
> I think this thread is about individual cell modules, so low voltage. 
> But I had to remind everyone not to take that above sentence out of 
> context. Bob
I think the thread is about balancing a pack.  Though he did not inform 
us of the number of cells, I would guess 40-45.

I suggested that the easiest way to balance is to contrive to charge at 
a current around the capacity of the miniBMS modules to bypass. Then, 
charge for long enough, perhaps days, to allow all modules to begin 
bypassing.
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Re: [EVDL] Suitable Load?

[Mike Beem via EV]

Thank you all for the suggestions and guidance, based on your experience.
Tom W got it, I had 8 out of 40 cells ahead of the pack yesterday when I
last worked on it, (between going back up to the house and checking the
replies), and I can do what he did, using the same set up.
And, as always, I appreciate Lee Hart's EE input--I did not know that about
lamps (light bulbs), but as with everything else he has shared with me
through the years, it makes sense.
It is because of the great EV pioneers and developers on this list being
willing to share their knowledge with every questioner willing to listen
and learn who make it possible for people like me to drive EV's year after
year. I came here in 1999 seeking help with my 1st EV project, and it has
made my driving life SO much more fun for all the years after-
Still got the EV grin!!
Michael B

On Thu, Nov 5, 2015 at 7:04 AM, tomw via EV  wrote:

> What portion of cells in the pack are at significantly higer SoC?  I assume
> it is a small portion, or you would be individually charging the smaller
> portion of cells which are at lower SoC.  I've done both. For higher SoC
> cells I connect a 3 Ohm 10W resistor between the terminals with spring
> clips
> so it shunts more current once the red LED lights on the minibms.  This
> usually keeps it from going over 3.55V while the other cells are charging,
> but if you have severe imbalance it may not keep it below that voltage long
> enough for the others to charge up.  In that case I stop charging the pack
> and continue bleeding the high cell for "a while" which is a guess at how
> many Ah I need to remove from it.  I put the resistor inside a piece of pvc
> pipe so it is suspended inside by the wires, not touching the pipe since it
> gets fairly hot.  Pipe ends are left mostly open for some ventilation.  The
> timer would be a good safety device, but its setting is still just a guess
> for how long you need to discharge.  Might be too long or too short.  I
> like
> to just monitor cell V with a DVM.  I have discharge curves I took years
> ago
> using a celllog8, so I have some idea of how much charge I need to remove
> to
> bring that cell into balance - but only roughly since the cells vary in V
> versus SoC. I hang a kitchen timer/alarm around my neck to remind me to
> check every x minutes, depending on how severe the imbalance is.
>
> I've also done the converse, charging individual cells with a DC voltage
> supply.  After charging the higher SoC cells fully (to 3.5V for me), I set
> the supply to 3.5V and let it charge each low one, one at a time.  Don't
> have to watch it like you do bleeding with a resistor since it won't charge
> above 3.5V, but it lowers current as it approaches that value so can take
> several hours to charge a cell if it is at significantly different SoC than
> the others.  I've only had significant imbalance like this when changing
> from no bms to the minibms years ago, or when replacing a cell.  Since I
> don't have to watch charging with the DC supply, I found it easier to just
> leave the 3 Ohm resistor on the high cell long enough to bring it below the
> other cells in SoC, then charged the pack, then individually charged that
> cell.
>
> --
> View this message in context:
> http://electric-vehicle-discussion-list.413529.n4.nabble.com/Suitable-Load-tp4678485p4678511.html
> Sent from the Electric Vehicle Discussion List mailing list archive at
> Nabble.com.
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Re: [EVDL] Suitable Load?

[Robert Bruninga via EV]

And if hasn't been said, light bulbs are the best load because they have a
negative resistance component and will provide a more constant load as the
voltage drops.

Bob


-Original Message-
From: EV [mailto:ev-boun...@lists.evdl.org] On Behalf Of Mike Beem via EV
Sent: Thursday, November 05, 2015 2:03 PM
To: tomw; Electric Vehicle Discussion List
Subject: Re: [EVDL] Suitable Load?

Thank you all for the suggestions and guidance, based on your experience.
Tom W got it, I had 8 out of 40 cells ahead of the pack yesterday when I
last worked on it, (between going back up to the house and checking the
replies), and I can do what he did, using the same set up.
And, as always, I appreciate Lee Hart's EE input--I did not know that
about lamps (light bulbs), but as with everything else he has shared with
me through the years, it makes sense.
It is because of the great EV pioneers and developers on this list being
willing to share their knowledge with every questioner willing to listen
and learn who make it possible for people like me to drive EV's year after
year. I came here in 1999 seeking help with my 1st EV project, and it has
made my driving life SO much more fun for all the years after- Still got
the EV grin!!
Michael B

On Thu, Nov 5, 2015 at 7:04 AM, tomw via EV <ev@lists.evdl.org> wrote:

> What portion of cells in the pack are at significantly higer SoC?  I
> assume it is a small portion, or you would be individually charging
> the smaller portion of cells which are at lower SoC.  I've done both.
> For higher SoC cells I connect a 3 Ohm 10W resistor between the
> terminals with spring clips so it shunts more current once the red LED
> lights on the minibms.  This usually keeps it from going over 3.55V
> while the other cells are charging, but if you have severe imbalance
> it may not keep it below that voltage long enough for the others to
> charge up.  In that case I stop charging the pack and continue
> bleeding the high cell for "a while" which is a guess at how many Ah I
> need to remove from it.  I put the resistor inside a piece of pvc pipe
> so it is suspended inside by the wires, not touching the pipe since it
> gets fairly hot.  Pipe ends are left mostly open for some ventilation.
> The timer would be a good safety device, but its setting is still just
> a guess for how long you need to discharge.  Might be too long or too
> short.  I like to just monitor cell V with a DVM.  I have discharge
> curves I took years ago using a celllog8, so I have some idea of how
> much charge I need to remove to bring that cell into balance - but
> only roughly since the cells vary in V versus SoC. I hang a kitchen
> timer/alarm around my neck to remind me to check every x minutes,
> depending on how severe the imbalance is.
>
> I've also done the converse, charging individual cells with a DC
> voltage supply.  After charging the higher SoC cells fully (to 3.5V
> for me), I set the supply to 3.5V and let it charge each low one, one
> at a time.  Don't have to watch it like you do bleeding with a
> resistor since it won't charge above 3.5V, but it lowers current as it
> approaches that value so can take several hours to charge a cell if it
> is at significantly different SoC than the others.  I've only had
> significant imbalance like this when changing from no bms to the
> minibms years ago, or when replacing a cell.  Since I don't have to
> watch charging with the DC supply, I found it easier to just leave the
> 3 Ohm resistor on the high cell long enough to bring it below the
> other cells in SoC, then charged the pack, then individually charged
that cell.
>
> --
> View this message in context:
> http://electric-vehicle-discussion-list.413529.n4.nabble.com/Suitable-
> Load-tp4678485p4678511.html Sent from the Electric Vehicle Discussion
> List mailing list archive at Nabble.com.
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> racing at NEDRA (
> http://groups.yahoo.com/group/NEDRA)
>
>
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Re: [EVDL] Suitable Load?

[paul dove via EV]

Yes, Ohms law applies in light bulbs.
Instead of a linear graph you get a curve because of the changing resistance.As 
the voltage increases the current increase becomes smaller and smaller.Since it 
is not linear the change in current slows down as the voltage increases.Still, 
at low voltage you have low current and at high voltage you have high current 
as I said.




  From: Lee Hart <leeah...@earthlink.net>
 To: Paul Dove <dov...@bellsouth.net>; Electric Vehicle Discussion List 
<ev@lists.evdl.org> 
 Sent: Thursday, November 5, 2015 11:01 AM
 Subject: Re: [EVDL] Suitable Load?
   
Paul Dove via EV wrote:
> Halogen bulbs are made in general for 6V, 12V, 24V... Using too low
> a voltage will produce little current and too high a voltage will
> produce high current and overheating of the filament

Actually, light bulbs don't behave like resistors. Ohm's law doesn't 
apply. :-)

A light bulb's apparent resistance changes drastically with temperature. 
The cold resistance (measured with an ohmmeter) is easily 1:10th that of 
its hot resistance (current divided by voltage at full rated voltage). 
Depending on the type of light, an 8-1 change in voltage only causes 
about a 2:1 change in current.

This means that light bulbs can be used as crude constant-current loads. 
The current only changes slightly despite large changes in voltage. This 
characteristic is ideal for testing batteries, where you'd like the 
current to stay the same despite changes in cell or battery voltage.
-- 
Any intelligent fool can make things bigger, more complex, and more
violent. It takes a touch of genius, and a lot of courage, to move
in the opposite direction. -- Albert Einstein
--
Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com


   
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Re: [EVDL] Suitable Load?

[Peri Hartman via EV]

I thought the resistance was dependent on temperature, not voltage.   
Sure, a higher voltage means it will heat up quicker and increase in 
resistance quicker.  But initially, at least, for a given voltage, the 
resistance would be low.  Thus, resistance would not proportional to 
voltage.  Did I miss something?


Peri

-- Original Message --
From: "paul dove via EV" <ev@lists.evdl.org>
To: "Lee Hart" <leeah...@earthlink.net>; "Electric Vehicle Discussion 
List" <ev@lists.evdl.org>

Sent: 05-Nov-15 12:53:10 PM
Subject: Re: [EVDL] Suitable Load?


Yes, Ohms law applies in light bulbs.
Instead of a linear graph you get a curve because of the changing 
resistance.As the voltage increases the current increase becomes 
smaller and smaller.Since it is not linear the change in current slows 
down as the voltage increases.Still, at low voltage you have low 
current and at high voltage you have high current as I said.





  From: Lee Hart <leeah...@earthlink.net>
 To: Paul Dove <dov...@bellsouth.net>; Electric Vehicle Discussion List 
<ev@lists.evdl.org>

 Sent: Thursday, November 5, 2015 11:01 AM
 Subject: Re: [EVDL] Suitable Load?

Paul Dove via EV wrote:

 Halogen bulbs are made in general for 6V, 12V, 24V... Using too low
 a voltage will produce little current and too high a voltage will
 produce high current and overheating of the filament


Actually, light bulbs don't behave like resistors. Ohm's law doesn't
apply. :-)

A light bulb's apparent resistance changes drastically with 
temperature.
The cold resistance (measured with an ohmmeter) is easily 1:10th that 
of

its hot resistance (current divided by voltage at full rated voltage).
Depending on the type of light, an 8-1 change in voltage only causes
about a 2:1 change in current.

This means that light bulbs can be used as crude constant-current 
loads.
The current only changes slightly despite large changes in voltage. 
This

characteristic is ideal for testing batteries, where you'd like the
current to stay the same despite changes in cell or battery voltage.
--
Any intelligent fool can make things bigger, more complex, and more
violent. It takes a touch of genius, and a lot of courage, to move
in the opposite direction. -- Albert Einstein
--
Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com



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Re: [EVDL] Suitable Load?

[Lawrence Harris via EV]

Yes but temperature is affected by current which is affected by voltage so in 
some sense instantaneous resistance is a function of voltage.
The instantaneous resistance will be a factor of of the base material, amount 
the resistance changes due to temperature and the current temperature.  The 
current temperature is dependant on the voltage applied and for how long and 
how well the material can radiate heat and how well the environment can conduct 
heat away.

Hence I = V/R is not a very good approximation in this environment.  While it 
may still hold for any given instantaneous moment in time it’s mostly useless 
as predictor when all of I, V and R vary with changes in all three values over 
time.  You are better off to test the circuit and measure what it does.

Lawrence

> On Nov 5, 2015, at 1:12 PM, Peri Hartman via EV <ev@lists.evdl.org> wrote:
> 
> I thought the resistance was dependent on temperature, not voltage.   Sure, a 
> higher voltage means it will heat up quicker and increase in resistance 
> quicker.  But initially, at least, for a given voltage, the resistance would 
> be low.  Thus, resistance would not proportional to voltage.  Did I miss 
> something?
> 
> Peri
> 
> -- Original Message --
> From: "paul dove via EV" <ev@lists.evdl.org>
> To: "Lee Hart" <leeah...@earthlink.net>; "Electric Vehicle Discussion List" 
> <ev@lists.evdl.org>
> Sent: 05-Nov-15 12:53:10 PM
> Subject: Re: [EVDL] Suitable Load?
> 
>> Yes, Ohms law applies in light bulbs.
>> Instead of a linear graph you get a curve because of the changing 
>> resistance.As the voltage increases the current increase becomes smaller and 
>> smaller.Since it is not linear the change in current slows down as the 
>> voltage increases.Still, at low voltage you have low current and at high 
>> voltage you have high current as I said.
>> 
>> 
>> 
>> 
>>  From: Lee Hart <leeah...@earthlink.net>
>> To: Paul Dove <dov...@bellsouth.net>; Electric Vehicle Discussion List 
>> <ev@lists.evdl.org>
>> Sent: Thursday, November 5, 2015 11:01 AM
>> Subject: Re: [EVDL] Suitable Load?
>> 
>> Paul Dove via EV wrote:
>>> Halogen bulbs are made in general for 6V, 12V, 24V... Using too low
>>> a voltage will produce little current and too high a voltage will
>>> produce high current and overheating of the filament
>> 
>> Actually, light bulbs don't behave like resistors. Ohm's law doesn't
>> apply. :-)
>> 
>> A light bulb's apparent resistance changes drastically with temperature.
>> The cold resistance (measured with an ohmmeter) is easily 1:10th that of
>> its hot resistance (current divided by voltage at full rated voltage).
>> Depending on the type of light, an 8-1 change in voltage only causes
>> about a 2:1 change in current.
>> 
>> This means that light bulbs can be used as crude constant-current loads.
>> The current only changes slightly despite large changes in voltage. This
>> characteristic is ideal for testing batteries, where you'd like the
>> current to stay the same despite changes in cell or battery voltage.
>> --
>> Any intelligent fool can make things bigger, more complex, and more
>> violent. It takes a touch of genius, and a lot of courage, to move
>> in the opposite direction. -- Albert Einstein
>> --
>> Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com
>> 
>> 
>> 
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Re: [EVDL] Suitable Load?

[Willie2 via EV]

On 11/05/2015 07:44 AM, Robert Bruninga via EV wrote:
I think this thread is about individual cell modules, so low voltage. 
But I had to remind everyone not to take that above sentence out of 
context. Bob
I think the thread is about balancing a pack.  Though he did not inform 
us of the number of cells, I would guess 40-45.


I suggested that the easiest way to balance is to contrive to charge at 
a current around the capacity of the miniBMS modules to bypass. Then, 
charge for long enough, perhaps days, to allow all modules to begin 
bypassing.

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Re: [EVDL] Suitable Load?

[tomw via EV]

What portion of cells in the pack are at significantly higer SoC?  I assume
it is a small portion, or you would be individually charging the smaller
portion of cells which are at lower SoC.  I've done both. For higher SoC
cells I connect a 3 Ohm 10W resistor between the terminals with spring clips
so it shunts more current once the red LED lights on the minibms.  This
usually keeps it from going over 3.55V while the other cells are charging,
but if you have severe imbalance it may not keep it below that voltage long
enough for the others to charge up.  In that case I stop charging the pack
and continue bleeding the high cell for "a while" which is a guess at how
many Ah I need to remove from it.  I put the resistor inside a piece of pvc
pipe so it is suspended inside by the wires, not touching the pipe since it
gets fairly hot.  Pipe ends are left mostly open for some ventilation.  The
timer would be a good safety device, but its setting is still just a guess
for how long you need to discharge.  Might be too long or too short.  I like
to just monitor cell V with a DVM.  I have discharge curves I took years ago
using a celllog8, so I have some idea of how much charge I need to remove to
bring that cell into balance - but only roughly since the cells vary in V
versus SoC. I hang a kitchen timer/alarm around my neck to remind me to
check every x minutes, depending on how severe the imbalance is.

I've also done the converse, charging individual cells with a DC voltage
supply.  After charging the higher SoC cells fully (to 3.5V for me), I set
the supply to 3.5V and let it charge each low one, one at a time.  Don't
have to watch it like you do bleeding with a resistor since it won't charge
above 3.5V, but it lowers current as it approaches that value so can take
several hours to charge a cell if it is at significantly different SoC than
the others.  I've only had significant imbalance like this when changing
from no bms to the minibms years ago, or when replacing a cell.  Since I
don't have to watch charging with the DC supply, I found it easier to just
leave the 3 Ohm resistor on the high cell long enough to bring it below the
other cells in SoC, then charged the pack, then individually charged that
cell. 

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Re: [EVDL] Suitable Load?

[Robert Bruninga via EV]

> spring-wound bathroom timer ... works fine for AC or DC ...15-20 amps.

Reminder:  But ONLY AT LOW VOLTAGE DC.  Use it once at any higher voltage
on DC, and when the contacts open, and arc will not only burn it up, but
probably catch it on fire.

Solution of course is to put a snubber resistor and capacitor across the
contacts.  But without that, it will not open a HVDC circuit,... just arc
and burn.

I think this thread is about individual cell modules, so low voltage.  But
I had to remind everyone not to take that above sentence out of context.
Bob

On Wed, Nov 4, 2015 at 9:19 PM, Lee Hart via EV  wrote:

> Mike Beem via EV wrote:
>
>> I have been trying to re-balance my 4 year old 100Ah CALB pack with
>> mini-BMS... I don't have any other suitable DC lamps or other safe
>> (to me) items which I can guarantee won't damage a cell by my
>> inattention... What suggestions do people have for me?
>>
>
> A couple things come to mind:
>
> First, you can get a spring-wound bathroom fan timer (Intermatic is one
> brand). They are sold at Home Depot, Menards, etc. for $15 or so. It
> installs in a normal electrical box like a light switch. It uses no power,
> and so works fine for AC or DC to switch loads up to 15-20 amps.
>
> Use it to switch your lamp or other resistive load across a cell or
> battery. The knob usually goes from 0-60 minutes (though 0-4 hour and 0-12
> hour versions are also available). It will automatically shut off the load
> even if you forget! There are versions that have a "continuous on" position
> at the end, and versions that don't -- for this application you want the
> kind that don't. And it doesn't need AC power, and there are no batteries
> to go dead.
>
> Another option is to put a string of ordinary silicon diodes in series
> with your lamp or resistive load. Each diode drops about 0.6v-0.8v at its
> rated current, and essentially stop conducting below 0.5v. So a string of
> (say) 6 diodes automatically removes the load when the cell goes below 6 x
> 0.5v = 3.0 volts.
>
> --
> Any intelligent fool can make things bigger, more complex, and more
> violent. It takes a touch of genius, and a lot of courage, to move
> in the opposite direction. -- Albert Einstein
> --
> Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com
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[EVDL] Suitable Load?

[Mike Beem via EV]

I have been trying to re-balance my 4 year old 100Ah CALB pack with
mini-BMS, identifying the highest SOC cells by watching for the red LED's
to light up on the mini-BMS boards on the individual cells. I have been
using a 12 volt, 50 watt "A" lamp, leaving it on the cells one at time for
60-90 minutes  each, then bringing the full pack up again until I start
seeing red LED's.
I don't have any other suitable DC lamps or other safe (to me) items which
I can guarantee won't damage a cell by my inattention (I set an alarm for
myself every time I connect this load to a cell).
What suggestions do people have for me? How would a 120 volt 500 watt
halogen affect one of these individual nominal 3 volt cell (resting is
actually ~ 3.3v)?
 It was my intention 4 years ago when I re-converted the EV Escort to
lithium to see if I could drive an EV for 10 years on a $10,000 layout, not
counting brakes and other expendables. So far, I have seen no loss of
range, and have no indications of degradation.
I set myself up for the current balancing problem by charging individual
cells while the PFC30 was back in Washington for a minor repair, so now I
have high SOC cells turning off the charger before the pack is fully
charged.

Thank you!
Michael B
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Re: [EVDL] Suitable Load?

[Lee Hart via EV]

Mike Beem via EV wrote:

I have been trying to re-balance my 4 year old 100Ah CALB pack with
mini-BMS... I don't have any other suitable DC lamps or other safe
(to me) items which I can guarantee won't damage a cell by my
inattention... What suggestions do people have for me?


A couple things come to mind:

First, you can get a spring-wound bathroom fan timer (Intermatic is one 
brand). They are sold at Home Depot, Menards, etc. for $15 or so. It 
installs in a normal electrical box like a light switch. It uses no 
power, and so works fine for AC or DC to switch loads up to 15-20 amps.


Use it to switch your lamp or other resistive load across a cell or 
battery. The knob usually goes from 0-60 minutes (though 0-4 hour and 
0-12 hour versions are also available). It will automatically shut off 
the load even if you forget! There are versions that have a "continuous 
on" position at the end, and versions that don't -- for this application 
you want the kind that don't. And it doesn't need AC power, and there 
are no batteries to go dead.


Another option is to put a string of ordinary silicon diodes in series 
with your lamp or resistive load. Each diode drops about 0.6v-0.8v at 
its rated current, and essentially stop conducting below 0.5v. So a 
string of (say) 6 diodes automatically removes the load when the cell 
goes below 6 x 0.5v = 3.0 volts.


--
Any intelligent fool can make things bigger, more complex, and more
violent. It takes a touch of genius, and a lot of courage, to move
in the opposite direction. -- Albert Einstein
--
Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com
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Re: [EVDL] Suitable Load?

[Willie2 via EV]

On 11/04/2015 06:39 PM, Mike Beem via EV wrote:

I have been trying to re-balance my 4 year old 100Ah CALB pack with
mini-BMS, identifying the highest SOC cells by watching for the red LED's

I've had pretty good luck limiting charge current to close to the 
miniBMS by-pass capabilities.  You can run charging current through an 
incandescent bulb (thanks, Lee)  and/or find a charging set up that will 
charge at only an amp or two.

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Re: [EVDL] Suitable Load?

[Mike Nickerson via EV]

My solution to this problem was to buy an RC model charger that supported 
LiFePO4 batteries.  If really out of balance, I would charge one cell at a 
time.  If closer, I would charge up to 5 cells in a string.  The charger would 
taper before the MiniBMS alerted.  It also has low enough current that the 
MiniBMS bypass resistors could keep up.  A weekend moving the charger down the 
string did the trick.  It also shows how many Ah it puts in each cell.

This worked well.  It also checked for things like being hooked up backwards.

I think mine went by SkyCharger.  It was about $50 on Amazon.  It also supports 
NiCd and lead-acid.

Mike


On November 4, 2015 5:39:33 PM MST, Mike Beem via EV  wrote:
>I have been trying to re-balance my 4 year old 100Ah CALB pack with
>mini-BMS, identifying the highest SOC cells by watching for the red
>LED's
>to light up on the mini-BMS boards on the individual cells. I have been
>using a 12 volt, 50 watt "A" lamp, leaving it on the cells one at time
>for
>60-90 minutes  each, then bringing the full pack up again until I start
>seeing red LED's.
>I don't have any other suitable DC lamps or other safe (to me) items
>which
>I can guarantee won't damage a cell by my inattention (I set an alarm
>for
>myself every time I connect this load to a cell).
>What suggestions do people have for me? How would a 120 volt 500 watt
>halogen affect one of these individual nominal 3 volt cell (resting is
>actually ~ 3.3v)?
> It was my intention 4 years ago when I re-converted the EV Escort to
>lithium to see if I could drive an EV for 10 years on a $10,000 layout,
>not
>counting brakes and other expendables. So far, I have seen no loss of
>range, and have no indications of degradation.
>I set myself up for the current balancing problem by charging
>individual
>cells while the PFC30 was back in Washington for a minor repair, so now
>I
>have high SOC cells turning off the charger before the pack is fully
>charged.
>
>Thank you!
>Michael B
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Re: [EVDL] Suitable Load?

[Paul Dove via EV]

Halogen bulbs are made in general for 6V, 12V, 24V. To run the lamps on 120v AC 
a transformer is needed. A rectification is not needed because the bulbs work 
with AC and DC. The halogen lamp is an advanced form of incandescent lamp.

Using too low a voltage will produce little current and too high a voltage will 
produce high current and overheating of the filament 


Sent from my iPad

> On Nov 4, 2015, at 6:39 PM, Mike Beem via EV  wrote:
> 
> I have been trying to re-balance my 4 year old 100Ah CALB pack with
> mini-BMS, identifying the highest SOC cells by watching for the red LED's
> to light up on the mini-BMS boards on the individual cells. I have been
> using a 12 volt, 50 watt "A" lamp, leaving it on the cells one at time for
> 60-90 minutes  each, then bringing the full pack up again until I start
> seeing red LED's.
> I don't have any other suitable DC lamps or other safe (to me) items which
> I can guarantee won't damage a cell by my inattention (I set an alarm for
> myself every time I connect this load to a cell).
> What suggestions do people have for me? How would a 120 volt 500 watt
> halogen affect one of these individual nominal 3 volt cell (resting is
> actually ~ 3.3v)?
> It was my intention 4 years ago when I re-converted the EV Escort to
> lithium to see if I could drive an EV for 10 years on a $10,000 layout, not
> counting brakes and other expendables. So far, I have seen no loss of
> range, and have no indications of degradation.
> I set myself up for the current balancing problem by charging individual
> cells while the PFC30 was back in Washington for a minor repair, so now I
> have high SOC cells turning off the charger before the pack is fully
> charged.
> 
> Thank you!
> Michael B
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Re: [EVDL] Suitable Load?

[Alan Arrison via EV]

I can pretty much guarantee you there is degradation in 4 years.
A friend of mine just parted out his conversion and I bought his CALB 
100Ah cells.

They are 3 years old with only 8000 miles on them.
He did not use a BMS, but they were top balanced when new.
Charge cutoff voltage was kept conservatively low.
I charged each cell individually and then discharged at a constant 30A 
to 3.00V.

The amp hours and watt hours were totaled and recorded.

Ah varied from 88 to 96 and Wh varied from 310 to 280.
Internal resistance varied widely as well and there were 3 duds that 
were way out of spec.

As Mike said, an RC charger can charge/discharge cells and track Ah.
Discharge rates are usually max of 100W or about 30A for a 3.2V cell 
which is fine for a 100Ah cell.

Check Thundersky.com

Al


On 11/4/2015 7:39 PM, Mike Beem via EV wrote:

I have been trying to re-balance my 4 year old 100Ah CALB pack with
mini-BMS, identifying the highest SOC cells by watching for the red LED's
to light up on the mini-BMS boards on the individual cells. I have been
using a 12 volt, 50 watt "A" lamp, leaving it on the cells one at time for
60-90 minutes  each, then bringing the full pack up again until I start
seeing red LED's.
I don't have any other suitable DC lamps or other safe (to me) items which
I can guarantee won't damage a cell by my inattention (I set an alarm for
myself every time I connect this load to a cell).
What suggestions do people have for me? How would a 120 volt 500 watt
halogen affect one of these individual nominal 3 volt cell (resting is
actually ~ 3.3v)?
  It was my intention 4 years ago when I re-converted the EV Escort to
lithium to see if I could drive an EV for 10 years on a $10,000 layout, not
counting brakes and other expendables. So far, I have seen no loss of
range, and have no indications of degradation.
I set myself up for the current balancing problem by charging individual
cells while the PFC30 was back in Washington for a minor repair, so now I
have high SOC cells turning off the charger before the pack is fully
charged.

Thank you!
Michael B
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