Is my Battery's BMS working properly

Batteries, Chargers, and Battery Management Systems.
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MartinBuckley   1 µW

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Joined: Jun 01 2018 5:21pm

Is my Battery's BMS working properly

Post by MartinBuckley » Jun 21 2018 12:20pm

Recently converted an old hybrid street bike to electric, adding a Bafang BBS02 mid engine and a 52V 17A triangle battery, from a reputable online vendor. Also purchased a Lekke 36T Chainring and larger geared cassette to ensure that the BBS02 can rev high to safely climb hills.

After the third ride/charge cycle the battery reached 58.8V, so performed a couple of charge cycles to 90%, using the same vendors smart charger.

From the fifth charge onward, have been charging to 100%, because when the charger suspends, the battery is only at 58.1-58.3V.

Per guidance from other threads, have been leaving charger on for extended periods of time, to allow balancing to progress.

~5 charge cycles were at least 8-36 hours duration, while using bike to commute to work every other day or so.

Concerning power consumption:
- Total miles biking is 230 miles.
- Bike and rider in the 320LB range.
- The commute is ~8 miles each way. The ride to work is gradually up hill, on dirt/stone dust, for 4 miles, 2 miles on paved bike trails, with the last 2 miles on road 200+ feet rise. Using throttle liberally during commute. The ride home is a delightful down hill rush.
- Have also biked a few 2+ hour cruises, at speed and with a fair amount of slightly steep hills, some significantly large than the commute hill. Location in central Ma., rural with lots of rolling hills, mostly biking on tarred roads.
- The battery has never been drained below 46V.
- The round trip commute usually consumes 6-7V, draining the battery to no less than 49.8V.

The duration of the latest charge cycle is approaching 60 hours. After initial charge, battery voltage was 58.1V. Since then, voltage has dropped to 57.9V.

Bike and charger are in the middle of concrete floor of standalone garage.

Though I am not that worried about torching the garage, I am concerned about the lack of progress balancing. How long should I leave charging and is current usage "light enough" to not interfere with the balancing process.

How much longer should I wait before deciding that the pack may have bad/marginal cells or the BMS isn't working properly?

Suggestions & recommendations greatly appreciated.

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