A customer brought in a Chi Gladiator 60v 60Ah battery pack for repair. The pack was at 15% SOC, the display would not light, and the pack would not take a charge, so I suspected that something was wrong with the BMS. OK, so how do we get into this thing? Turns out that there are many, many layers of shrink wrap, plastic wrap, fiberglass sheet, fiberglass tape, fish paper and loads of black silicone adhesive to get through just to get the lid off. I'm actually happy to see that Chi is moving toward a sealed canister (which I hope has a watertight removable lid) for the next gen of their packs as this thing is so difficult to service.
The Chi battery pack is very well constructed from the available materials, but I think there is definitely work to be done on the case to make it more serviceable. Inside, we find a CLRD 30A BMS, which I was a bit surprised to discover. However, upon closer examination, I learned that the battery is running in bypassed mode, with the full pack current going directly to the output terminals. I'm not sure how I feel about this yet, as this pack could probably put out several hundred amps from the Molicel P42A's in 16S 14P configuration.
Upon peeling away all of the fish paper so we could check the voltage level in each group, I detected that the bottom half of the battery was very wet. You can see the dark colored green fish paper where the pack is soaked.
I was finally able to gain access to all of the balance leads and with a bit of creative spreadsheet work, I determined which cell group was low. This step was necessary because the BMS wouldn't respond to BTLE communications so I had no idea if we had a low cell group and if so, which one it was. Turns out that there were two groups that were low and these also happened to be the groups that were the most wet. So, I dried out the back good with a fan for several hours, brought up the low groups, reset the BMS and the pack came back to life! I was then able to connect to the BTLE app and check on the balance status of the pack, which at this point looks OK. We still have some stress testing to do on this pack to determine if the repair is robust, but it's looking promising. Resealing this pack is going to be another question entirely, and then there is also the issue of keeping it absolutely dry in the future, something that is pretty challenging with an off-road vehicle battery.
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