Battery BMS failed for second time

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Thomsontouring   1 mW

1 mW
Posts: 10
Joined: Jun 19 2018 3:40pm

Battery BMS failed for second time

Post by Thomsontouring » Sep 21 2018 8:15am

I'm posting this to find out if anybody has had a similar experience, or any advice. I'm not in any way trying to disparage the reputable vendor (em3ev) who provided my kit and I'm sure will stand by their product and get my bike running again. This is the fairly generic kit I bought - my fourth build from this vendor.
- BBS02 motor set up for 18 Amps
- 41s4P Super Shark battery, 52v nominal, 35E cells
- SmartBMS with bluetooth
- DC P14 color display
- 2A plastic charger from Em3ev

I built this onto a 24" Schwinn Sidewinder from Walmart for a 12 year old kid. The only unusual thing I noticed was that the 2A charger got considerably hotter than the 5A chargers I have used before. The bike ran for a week, perhaps 3 charge cycles and 35 miles, when it suddenly quit. At the time the display was showing a nearly full 57.7 volts. On opening the battery I found all the cell groups balanced and the whole pack still at full voltage, but nothing coming through the BMS although there was no visible damage. Attempts to reboot the BMS failed, and in a couple of weeks I got a replacement BMS from the vendor and installed it.

The bike ran fine for another four days, and again lost power (no green lights on the battery). When connected to the charger, the top of the battery got hot so it was inspected again. This is what the BMS board looks like. Any clues? I really don't feel like swapping in a different battery if something else in the system is blowing these. Up to now I've had 100% reliability with these kits and have logged nearly 1000 miles on my first build.

The bike still works when powered with four 12v - 7Ah lead acid batteries I happened to have.
BMS1.jpg (118.91 KiB) Viewed 357 times

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