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[S10-EV] Signal Voltage to BPCM
Group - I forwarded the same retired GM engineer that worked on this
program your question. Here's his response: So here is the deal. The BPM (Battery Pack Module) commanded the TPIM
(Traction Power Inverter Module) with the amount of power the system could
use. I don't think it did any limiting as long as it believed the SOC
(State of Charge) was above a certain amount. More importantly, it
commanded the amount of regen that would be allowed based on SOC. If too
full, it would say no regen would be allowed to keep from cooking the
batteries and causing a "thermal event" It would seem to me that if someone really wanted to make one of these work
with different batteries, one would have to "fake out" the messages between
the TPIM and BPM. That would pretty much do it. I think it was all 8192
UART although the messages between the TPIM and BPM might have been Class
II. I can't remember. All other messages besides SOC might be able to be passed straight through.
And if you told it that it was 99% all of the time, it would effectively
disable regen. This would take a significant amount of work, but possible.
And with lithium, you wouldn't really miss the regen. From: bjnkm <[email removed]> To: Alan Martin <[email removed]>, [email removed] Date: Tue, 22 May 2018 10:35:23 -0400 Subject: Re: [S10-EV] S10-EV Digest, Vol 152, Issue 3 I'm building my lithium packs to 13 volt 60 AH. I have to limit charge
voltage to each of the 4 parallel packs that make up a module to 3.6v. I
looked into removing the BPCM but I would like to keep everything it
controls intact. -------- Original message -------- From: Alan Martin via S10-EV <[email removed]> Date: 5/21/18 9:49 AM (GMT-05:00) To: [email removed] Subject: Re: [S10-EV] S10-EV Digest, Vol 152, Issue 3 I would expect DTC131 to set in the PCM if the BCA measured voltage and
the BPCM voltage over UART do not agree in the situation you're describing. If you were to try rewiring the BPCM to measure all 27 modules between
J1-1 and J1-32 then you would expect to see BPCM DTC219 when the total pack
voltage does not agree with the max module voltage * 26. I'm planning to remove the BPCM from my truck as I convert to a modern
lithium pack. I think its easier to provide the few signals that the PCM
requires to be happy than it is to provide the many fake signals that the
BPCM requires to think that I still have a lead pack. -Al On Friday, May 18, 2018, 1:46:09 AM EDT, [email removed] <
[email removed]> wrote:: 1. Signal voltage to BPCM ([email removed]) Question for the group. If I were to add a 27th battery to my pack, there is obviously no signal
wire to the computer. Total pack voltage would rise by 12 volts to 324
volts, but the total sensor wire voltage would still be 312 volts. Would this
be a conflict to the BPCM? Without getting into a long detailed reason for this question right now,
I'm converting to LiFePo4 cells, and if there was no conflict it would be
much easier with the pre-assembled modules I have purchased. Thanks, Kevin McMullin
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program your question. Here's his response: So here is the deal. The BPM (Battery Pack Module) commanded the TPIM
(Traction Power Inverter Module) with the amount of power the system could
use. I don't think it did any limiting as long as it believed the SOC
(State of Charge) was above a certain amount. More importantly, it
commanded the amount of regen that would be allowed based on SOC. If too
full, it would say no regen would be allowed to keep from cooking the
batteries and causing a "thermal event" It would seem to me that if someone really wanted to make one of these work
with different batteries, one would have to "fake out" the messages between
the TPIM and BPM. That would pretty much do it. I think it was all 8192
UART although the messages between the TPIM and BPM might have been Class
II. I can't remember. All other messages besides SOC might be able to be passed straight through.
And if you told it that it was 99% all of the time, it would effectively
disable regen. This would take a significant amount of work, but possible.
And with lithium, you wouldn't really miss the regen. From: bjnkm <[email removed]> To: Alan Martin <[email removed]>, [email removed] Date: Tue, 22 May 2018 10:35:23 -0400 Subject: Re: [S10-EV] S10-EV Digest, Vol 152, Issue 3 I'm building my lithium packs to 13 volt 60 AH. I have to limit charge
voltage to each of the 4 parallel packs that make up a module to 3.6v. I
looked into removing the BPCM but I would like to keep everything it
controls intact. -------- Original message -------- From: Alan Martin via S10-EV <[email removed]> Date: 5/21/18 9:49 AM (GMT-05:00) To: [email removed] Subject: Re: [S10-EV] S10-EV Digest, Vol 152, Issue 3 I would expect DTC131 to set in the PCM if the BCA measured voltage and
the BPCM voltage over UART do not agree in the situation you're describing. If you were to try rewiring the BPCM to measure all 27 modules between
J1-1 and J1-32 then you would expect to see BPCM DTC219 when the total pack
voltage does not agree with the max module voltage * 26. I'm planning to remove the BPCM from my truck as I convert to a modern
lithium pack. I think its easier to provide the few signals that the PCM
requires to be happy than it is to provide the many fake signals that the
BPCM requires to think that I still have a lead pack. -Al On Friday, May 18, 2018, 1:46:09 AM EDT, [email removed] <
[email removed]> wrote:: 1. Signal voltage to BPCM ([email removed]) Question for the group. If I were to add a 27th battery to my pack, there is obviously no signal
wire to the computer. Total pack voltage would rise by 12 volts to 324
volts, but the total sensor wire voltage would still be 312 volts. Would this
be a conflict to the BPCM? Without getting into a long detailed reason for this question right now,
I'm converting to LiFePo4 cells, and if there was no conflict it would be
much easier with the pre-assembled modules I have purchased. Thanks, Kevin McMullin
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