Battery Percentage Dropping at Random

[ctuan13]

I just experienced something like this for the first time. I’m on vacation with only level 1 charging. The truck had been charging on level 1 for about 44 hours straight from 54% ish to 93%. I unplugged and went to the grocery store. Ride there was fine. On the 3 - 4 mile ride back the battery percentage started dropping rapidly from 91% to 82% in the span of just a couple miles. It seemed to stabilize at 82% so far. I parked and shut off the truck for now while I unload groceries. Hopefully this was just a BMS calculation error and not some indication of a bad battery module or something. No errors were thrown and no overheating or anything.

First thing I'd try is a 12V reset. Disconnect the negative battery terminal and leave it disconnected for 10 minutes. Reconnect. Unless it's a more serious problem, that should fix any issues!

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[ctuan13]

2025 Update
I haven't had any major issues with the battery pack since and battery SOH (State of Health) is still sitting at 100%! I'm back at my friends' place in Washington and made it here much faster with much more DC charging and less AC charging.

 

[MountainAlive]

Update on my battery percentage drop. I found a local level 2 charger and used that to charge up to about 95% and everything was fine. There seems to be some kind of software bug when level 1 charging above 90% in my case. The BMS wasn’t able to figure out just what state of charge the battery held until it drove for a while. I drove back from vacation today (~150 miles) and everything was fine.

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