Hybrid Battery Issue

Since you will likely have to replace modules on an ongoing basis, you may want to buy 1 small charger that is capable of charging/topping off a single module.

That way you can get the module close to the same voltage as the rest before sticking it in the pack.
Within 0.1v would be a good target.

The voltage won't matter quite as much if you are fully charging/discharging/balnacing the entire pack after before actually using it in the car.
But the closer you can get it, the better.

 

I cut a connector off a headlight and wired the high and low beams together. Throw in a switch and some meter leads and voila!

I do 3 cycles of reconditioning and then load test all modules. That way they've had a chance to improve if they're going to. I use a stopwatch to make sure they're under load for the same time. Then you'll be able to see how much they drop and compare values.

 

Do you watch the data live in your car after doing this?

Seems like it is easy enough to see who the laggards are over time. Also you could use an app to download/graph the data and just periodically look at that to preemptively see which one will be failing next.

 

That's fine.
My only comment would be SAFETY FIRST.
The Hybrid Battery is high voltage. Potentially deadly.

You may have 20 years experience keeping standard ICE vehicles going...but this is new uncharted territory.
Be careful.

 

You have done enough to confirm that module 5 is bad, but just a couple of comments on your methodology, which goes toward answering your "how to pick modules to purchase" question.

• Wire the high and low beams together in parallel to increase the current load.
• Let the discharge go for at least 120 secs.
• On your data sheet add a third column which is the delta of start and end voltage. (The end voltage is the voltage at the 120 sec mark before disconnecting from the battery.) So starting voltage (8.35 V) – ending voltage (8.22 V) = delta (0.13 V). This will make it easier to match with your replacement candidates, as you will do a similar charge/discharge/charge conditioning on your candidate modules before doing the load test. The module to choose in one that matches your existing modules.

Overall good work so far, you're well on your way to having a repaired battery.