[EVDL] Speaking of BMS. I have a question about the Chevy BMS for Bolt/Volt

[Peter VanDerWal via EV]

Does anyone know if anyone has repurposed batteries from a Chevy Volt/Bolt and 
used the original BMS on the battery pack?

I'm thinking about buying a pack from a wrecked Chevy and using it for my house 
battery. I figure it would be cheaper if I could use the original BMS instead 
of having to buy/build a new one.

Thanks, Pete.
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Re: [EVDL] Communicating over "mains" (Was: Minibms?)

[Lee Hart via EV]

Peri Hartman via EV wrote:

- Is it a safety system, there to prevent damage and fires?
(battery SAFETY system)

Doesn't matter. It can still be handled by a poll from a master.


For this to work, both the master and all the slaves have to be working. 
No failures. In a bus system (USB, CANbus, etc.) any failed device takes 
out the entire system.



In regard to your three example flavors, it seems that for a robust BMS
each individual cell monitor must do all three.


Yes. Most likely, there will be separate circuits for each, so one 
failure doesn't take them all out.



I'm out of my domain here, but can't balancing be handled by checking
cell voltage?


Measuring cell voltage only tells you that there might be a problem. It 
doesn't correct the problem, or even tell you what to do about it.


The fashionable way to balance is by switching a resistor (or some 
equivalent) across the cells if they get high while charging. There are 
issues with this, but it's generally the cheap way to do it. This is the 
"balancing" part of the three. Common failures here are a) the load 
didn't switch on when it should have, b) it didn't turn off when it 
should have, c) the charger didn't cut back, so it overwhelms the 
resistor and the cell overcharges anyway, d) the cells are too far out 
of balance for a small resistor to correct, e) insuring that the 
resistors aren't overheating due to excessive on-time.



What needs to be done for safety?


The safety circuits need to detect these failures, stop the charger (and 
driving, if regen could occur), and alter the driver that there's a 
problem that must be fixed.


Besides these, it needs to watch for other failure modes. Things like 
excessively high or low cell temperatures, excessively high or low 
voltages, loose terminals (such as by high terminal temperatures), and 
ground faults.


The safety circuits also need to be fail-safe. If something goes wrong 
with them, they *shut down* the vehicle rather than let you keep driving 
it unprotected.


Lee Hart

--
If happiness is on your mind, here's a daily list to find:
- something to do
- something to look forward to
- someone to love
- someone to take good care of
- and misbehave, just a little
--
Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com
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Re: [EVDL] Communicating over "mains" (Was: Minibms?)

[Lawrence Winiarski via EV]

Well, perhaps I'm wrong.   I suppose no one can see the future.   

But riddle me this :-).   Suppose you run a single wire out to 150 different 
batteries andyou have a good system.   Suppose ONE of those 300 different 
connections goes bad...
Wouldn't it be nice to be able to .even if everything was turned off, to 
have an alternatemethod of communicationthat didn't cost anything extra 
except a little software to twiddlethe balancing shunt...that could be used in 
a quiescent system to troubleshoot those 300 different connections?so you 
at least knew where to start taking stuff apart?

Perhaps I'm grasping at straws here, but I even see this stupid idea as useful.

 
 > From: Lee Hart 
> 
> All these problems are solvable if you throw enough engineering and 
> money at them. But it's not goiong to lead to a cheap simple system.
> 
> That's why everyone avoids using the propulsion wiring itself to carry 
> data. It's far cheaper and more reliable to run separate wires for data.

I agree there doesn't seem to be much practical advantage to re-using the 
traction power lines.

As a minimum, you'd need a filter at the controller. Caps are cheap, but a 500A 
choke is going to cost more than the #18 (or smaller) wire you'd have to run if 
you use dedicated wire. A huge ferrite bead might be enough for VHF and up.

That's why the whole "wideband over power line" never got out of the starting 
chute. You'd need a high-frequency bridge over every transformer in the system. 
I can see ten of them out my window — in a rural, low-density area!

I did play with the X-11 home power control protocol some decades ago, and 
built a Heathkit powerline-carrier intercom as a kid. But the grid wideband 
response is tremendously difficult to characterize, which I'd expect the 
traction bus to be, too. 

I've seen TDR graphs of different power line situations at different 
frequencies — it is totally unpredictable what characteristic impedance you can 
count on! The best scheme would probably be diversity spread spectrum, which 
ain't cheap.

 We need an energy policy that encourages consumption. -- George W. Bush 
 
 Jan Steinman, EcoReality Co-op  

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Re: [EVDL] Communicating over "mains" (Was: Minibms?)

[Jan Steinman via EV]

> From: Lee Hart 
> 
> All these problems are solvable if you throw enough engineering and 
> money at them. But it's not goiong to lead to a cheap simple system.
> 
> That's why everyone avoids using the propulsion wiring itself to carry 
> data. It's far cheaper and more reliable to run separate wires for data.

I agree there doesn't seem to be much practical advantage to re-using the 
traction power lines.

As a minimum, you'd need a filter at the controller. Caps are cheap, but a 500A 
choke is going to cost more than the #18 (or smaller) wire you'd have to run if 
you use dedicated wire. A huge ferrite bead might be enough for VHF and up.

That's why the whole "wideband over power line" never got out of the starting 
chute. You'd need a high-frequency bridge over every transformer in the system. 
I can see ten of them out my window — in a rural, low-density area!

I did play with the X-11 home power control protocol some decades ago, and 
built a Heathkit powerline-carrier intercom as a kid. But the grid wideband 
response is tremendously difficult to characterize, which I'd expect the 
traction bus to be, too. 

I've seen TDR graphs of different power line situations at different 
frequencies — it is totally unpredictable what characteristic impedance you can 
count on! The best scheme would probably be diversity spread spectrum, which 
ain't cheap.

 We need an energy policy that encourages consumption. -- George W. Bush 
 
 Jan Steinman, EcoReality Co-op  

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Re: [EVDL] Communicating over "mains" (Was: Minibms?)

[Lee Hart via EV]

Bill Dube via EV wrote:

The key is that the cell electronics are the simple part. They don't
have to be very sensitive or selective at all. They are just listening
to a a 100 kW radio station that is transmitting FM on its PWM carrier.
It is actually difficult _not_ to listen.


That's true. The problem is that this requires that the charger and 
controller be designed together with the BMS. That works for a big auto 
company. It does not work for small manufacturers or hobby EVs.



The transmission band can be in the high MHz, or low GHz band.


If it's in the low MHz range (AM radio), then switching transient from 
the sharp-edged charger and controller interfere. Try operating an AM 
radio in an EV with its antenna near the propulsion wiring.


If it's in the high MHz range (FM radio), then ringing and reflections 
within the wiring will create ghosts and echoes. These force the data 
rate way down into the range where controller and charger harmonics 
cause trouble. Look at what happens to a TTL signal at the end of a 3 
ft. piece of wire.


If it's in GHz range (cellphone frequencies), EV noise won't bother it. 
But then transmission line effects will create peaks and nulls every few 
inches.


All these problems are solvable if you throw enough engineering and 
money at them. But it's not goiong to lead to a cheap simple system.


That's why everyone avoids using the propulsion wiring itself to carry 
data. It's far cheaper and more reliable to run separate wires for data.


Lee Hart
--
If happiness is on your mind, here's a daily list to find:
- something to do
- something to look forward to
- someone to love
- someone to take good care of
- and misbehave, just a little
--
Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com
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Re: [EVDL] EV Digest, Vol 90, Issue 36

[Offgrid Systems via EV]

It's about source and receiver and signal strength. Ham guys don't' have 
their radios in the bowels of the machine, they have their antenna (and 
a power amp) outside the noise envelope. We are talking in dB of signal 
to noise ratios, you just don't have the luxury of having your power amp 
(much at all) and antenna outside the package. There is an acceptable 
error rate, and no usable signal. If you do the measurements and tests, 
I think you will agree.



t

On 4/28/2020 10:30 PM, Lawrence Winiarski wrote:
Isn't "Wide Band Noise" what RF guys overcome every day?   The reason 
you tune a radio is to ignore the 50 million other
channels and the sun/jupiter/everyelectronicdevice known to man and 
concentrate on your own..


I can use my cell phone in my EV just fine.   If noise was really 
insurmountable, then I wouldn't be able to do that.


Seems to me that with enough selectivity over enough time, you can 
ignore every bit of noise known to man.


As I said the Ham guys can pick out signal in signal to noise ratios 
of -120db.  That's 12 orders of magnitude and they can detect
a walkie/talkie on the other side of the globe.   It's amazing. Sure 
it's only a few bits/min, but the point is that it IS doable.


It requires a different mindset than just straight digital 
manipulation.   You accept error rates and deal with them using math.




On Tuesday, April 28, 2020, 9:58:47 PM PDT, Offgrid Systems via EV 
 wrote:



Yeah I'm gonna agree with Lee here. I've been thinking about this for
years also, going as far as testing some ac powerline comm chips adapted
to DC power busses. I found it's impossible with all the noise coming
from the drive on an EV.  But Lee, you don't even need a spectrum
analyser, just fire up your EV drive train, looking at any of the phases
with a oscilloscope. It's wide band noise, and the motor control is
modulating to operate the motor, but with sinewave drives, or even the
old PWM drives, there is noise during the entire cycle, and the only way
you get a quiet time is if you actually shut off and short the motor for
a brief period. But if you do that there will be high peak currents that
will not be good for the efficiency of the drive. If reliability is the
key, you will not want to use the DC busses, unless it's a low noise
application, and you can control and build all of the power devices,
like maybe a powerwall with a pure sinewave inverter, and you make the
charger (solar charge controller) and the inverter. But for motor
control, it's a difficult problem to solve.

Tim Economu

On 4/28/2020 6:48 PM, ev-requ...@lists.evdl.org 
<mailto:ev-requ...@lists.evdl.org> wrote:

> It sounds easy; but put a spectrum analyzer on your battery leads to see
> what's*really*  there. I think you'd be shocked at the noise level.
>
>> There are a few clever tricks you can employ. During charging, you can
>> have the charger pause for a regular "moment of silence" in which the
>> BMS can communicate quickly and in the clear without having to "shout"
>> over the charger PWM. Perhaps the same thing could occur to a lesser
>> extent with the inverter.
> Same as above. Are you going to design a special charger that must be
> used with your BMS?
>
> There are lots of solutions that work*some*  of the time. There are a
> few that work*most*  of the time. But it gets damnably difficult to find
> schemes that work*all*  of the time.
>
> The problem is that a BMS is a safety system that you want to work*all*
> of the time.
>
> Lee Hart

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--
With hope,

Tim Economu
Offgrid Systems LLC
7664 Hellman Road
Clinton, Wa 98236
offg...@whidbey.com
360-630-1962

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Re: [EVDL] .ie Tips for driving an electric car> (?laughable or sad?)

[Peter VanDerWal via EV]

I especially liked the part about not turning it on until you're ready to go or 
you'll drain the battery.  

I know if I turn my car on and have the radio blasting and the AC on, after an 
hour or so it will reduce my range by 1.5%.

I wonder what language it was originally written in?  Some of the translations 
to English were humorous and confusing.  

April 28, 2020 9:42 PM, "Peri Hartman via EV"  wrote:

> I think they should write instructions on how to make toast, too. Why 
> stop when you're so talented ?
> Peri
> 
> -- Original Message --
> From: "evln via EV" 
> To: ev@lists.evdl.org
> Cc: "evln" 
> Sent: 28-Apr-20 9:37:13 PM
> Subject: [EVDL] .ie Tips for driving an electric car> (?laughable or 
> sad?)
> 
>> (ireland media outlet)
>> https://intallaght.ie/tips-for-driving-an-electric-car-step-by-step
>> Tips for driving an electric car, step by step
>> 2020-04-29 ... make sure the car is not plugged in. If so, take a look at
>> charge level (Normally, you have some kind of LED ‘sneak’ so you can see it
>> from the outside ... Do not leave the door open longer than important. – Do
>> not press the start button until you are really going to start driving to
>> avoid draining the battery prematurely. – Turn off consumables (interior
>> lights, exterior lights, radio, air conditioning) ... (?idiotic?)
>> https://i2.wp.com/intallaght.ie/wp-content/uploads/2020/04/Tips-for-driving-an-electric-car-step-by-
>> tep.jpg
>> 
>> +
>> https://intallaght.ie/the-electric-bicycle-convertible-into-a-cargo-bike-that-can-carry-180-kilos-of
>> weight
>> The electric bicycle convertible into a cargo bike that can carry 180 Kilos
>> of weight
>> 2020-04-29 ... Bicycles are one-person vehicles, designed to transport a
>> single person. Some models offer a small basket to carry the backpack or a
>> small bag, and little else ...
>> https://i1.wp.com/intallaght.ie/wp-content/uploads/2020/04/The-electric-bicycle-convertible-into-a-c
>> rgo-bike-that-can.jpg
>> 
>> For EVLN EV-newswire posts view:
>> http://www.evdl.org/archive
>> https://mail-archive.com/ev@lists.evdl.org/maillist.html
>> 
>> {brucedp.neocities.org}
>> 
>> --
>> Sent from: http://electric-vehicle-discussion-list.413529.n4.nabble.com
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> 
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Re: [EVDL] Designing a lithium pack using reclaimed A123 cells.

[paul dove via EV]

http://liionbms.com/pdf/a123/charging.pdf

Sent from my iPhone

> On Apr 28, 2020, at 11:32 PM, Lawrence Rhodes via EV  
> wrote:
> 
> ANR26650M1A FS31-1A8 FH1010823-R-2
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Re: [EVDL] Communicating over "mains" (Was: Minibms?)

[Bill Dube via EV]

The key is that the cell electronics are the simple part. They don't 
have to be very sensitive or selective at all. They are just listening 
to a a 100 kW radio station that is transmitting FM on its PWM carrier. 
It is actually difficult _not_ to listen.


    The more sensitive receiver is the single central "brain" that is 
listening to the messages that the cell electronics are transmitting. 
This central brain is the most difficult part, but there is only one of 
them, so the cost of the system can be low overall.


    Again, you can _briefly_ pause the drive to listen, perhaps for a 
several milliseconds out of every second, and it would be imperceptible 
to the customer. I doubt that the motor would even notice. You might 
even listen between "on" pulses of the ~20 kHz PWM base frequency. The 
transmission band can be in the high MHz, or low GHz band.


    While charging, which is much more critical for safety, you can 
turn the charger off for much longer periods to get much more detailed 
information from the cell, if you like.


    When you are driving, you only need to hear from a cell when it is 
too hot, too cold, or low voltage. You also need some sort of cell roll 
call occasionally, but you can do that at a slow pace.


Bill D.



On 4/29/2020 5:30 PM, Lawrence Winiarski via EV wrote:

Isn't  "Wide Band Noise" what RF guys overcome every day?   The reason you tune 
a radio is to ignore the 50 million otherchannels and the 
sun/jupiter/everyelectronicdevice known to man and concentrate on your own..
I can use my cell phone in my EV just fine.   If noise was really 
insurmountable, then I wouldn't be able to do that.

Seems to me that with enough selectivity over enough time, you can ignore every 
bit of noise known to man.
As I said the Ham guys can pick out signal in signal to noise ratios of -120db. 
 That's 12 orders of magnitude and they can detecta walkie/talkie on the 
other side of the globe.   It's amazing.   Sure it's only a few bits/min, but 
the point is that it IS doable.

It requires a different mindset than just straight digital manipulation.   You 
accept error rates and deal with them using math.



On Tuesday, April 28, 2020, 9:58:47 PM PDT, Offgrid Systems via EV 
 wrote:
  
  Yeah I'm gonna agree with Lee here. I've been thinking about this for

years also, going as far as testing some ac powerline comm chips adapted
to DC power busses. I found it's impossible with all the noise coming
from the drive on an EV.  But Lee, you don't even need a spectrum
analyser, just fire up your EV drive train, looking at any of the phases
with a oscilloscope. It's wide band noise, and the motor control is
modulating to operate the motor, but with sinewave drives, or even the
old PWM drives, there is noise during the entire cycle, and the only way
you get a quiet time is if you actually shut off and short the motor for
a brief period. But if you do that there will be high peak currents that
will not be good for the efficiency of the drive. If reliability is the
key, you will not want to use the DC busses, unless it's a low noise
application, and you can control and build all of the power devices,
like maybe a powerwall with a pure sinewave inverter, and you make the
charger (solar charge controller) and the inverter. But for motor
control, it's a difficult problem to solve.

Tim Economu

On 4/28/2020 6:48 PM, ev-requ...@lists.evdl.org wrote:

It sounds easy; but put a spectrum analyzer on your battery leads to see
what's*really*  there. I think you'd be shocked at the noise level.


There are a few clever tricks you can employ. During charging, you can
have the charger pause for a regular "moment of silence" in which the
BMS can communicate quickly and in the clear without having to "shout"
over the charger PWM. Perhaps the same thing could occur to a lesser
extent with the inverter.

Same as above. Are you going to design a special charger that must be
used with your BMS?

There are lots of solutions that work*some*  of the time. There are a
few that work*most*  of the time. But it gets damnably difficult to find
schemes that work*all*  of the time.

The problem is that a BMS is a safety system that you want to work*all*
of the time.

Lee Hart



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