Alta battery pack rebalance capability

[Mark911]

Hello, this question is directed to the few individuals who have actually repaired a code 35/36 module/pack. How successful were you in getting the onboard BMS to re-balance the bad P-group(s) after the repair was made? My experience has been that without "bench balancing" to within a few hundredths of a volt prior to pack re-assembly the on-board system simply (even with the help of multitool) didn't have the power to re-balance a broken wirebond repair on its own.

 

[Rashid510]

Whats the repair? If its not a wirebond, its not going to work.

The BCU can balance within +/- 2mV. I usually go bit high on the module being re-installed as the voltage sag brings it within range.

 

[Mark911]

The cause if the imbalance is not of issue, my question is regarding experience with getting the module to re-balanced itself after repair simply using the BMS. For example, after a code 35/36 repair where one or more p-groups deviated by the rest by a tenth or so volt. My experience is that the stock BMS simply doesn't have the ability to bring these low p-groups back in line with the others making "Bench Balancing" of those p-groups necessary before reassembly of the pack. I'm not talking about what the system was designed to do, but what it can actually do. That's why I'm asking for input from those few individuals that have been personally involved with this type of situation.

 

[Rashid510]

Well, sans my input it seems (@snydes and @OneLapper can also probably provide data inputs), So far manually balancing an already "leaky" cell does not work as effective due to the cell already having some charge/discharge cycles. The BMS can only do so much on the balancing circuit side especially in the tenths of volts. Usually I try to find modules that can sustain the voltage difference. But once again my situation is probably different, hence you should get more data from others.

 

[snydes]

If I recall correctly I was only seeing something like 1.5 millivolt improvements after each balancing cycle on a copper fused reattached cell. Definitely want to bench balance a close as possible IMO.

 

[privateer703]

@snydes just installed a new module for me and it had a few p-groups that were slightly higher. I've only gone through a few balancing cycles but I will keep you updated. I will get a battery graph snapshot up here later today or tomorrow and then periodically update.

 

[Dirt-E]

I was going to ask in a separate post about bench balancing. Are there any threads about this so I'm not asking a bunch of the same things again?

I have a new 0 module that's way out from my original cells and need to bring them up to see if I can finally clear the 36 code and get it working again. I've got an idea how I can accomplish it, but why reinvent the wheel and risk getting it wrong?

 

[snydes]

I was going to ask in a separate post about bench balancing. Are there any threads about this so I'm not asking a bunch of the same things again?

I have a new 0 module that's way out from my original cells and need to bring them up to see if I can finally clear the 36 code and get it working again. I've got an idea how I can accomplish it, but why reinvent the wheel and risk getting it wrong?

You will need a DC power supply capable of charging a single module, such as a HP 6634A, and then charge that module separately.

 

[Dirt-E]

I ended up charging individual parallel banks until they were topped up enough to be close to the original cells.