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Fully charged shark pak 48v cuts out after a few minutes, I've read other threads.

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    Fully charged shark pak 48v cuts out after a few minutes, I've read other threads.

    Battery shuts off after successively shorter time

    I have 2 ebikes with identical setups. Bafang BBS02 motors, standard LCD display from Luna Cycles, a battery cradle mounted on each bike. I only have one 48v-13s-4p shark battery pack which I switch between the bikes. Combined I have 2,000 miles on the battery, 1200 on one bike, 800 on the other. The 1200 mile bike was assembled 2 years ago, the 800 mile bike one year ago. I go 10 to 20 miles between charges so between 100 and 200 partial discharge-recharge cycles. My range is about 45 miles to shut off discharge.

    Last week I was riding the 800 when the power shut off after 5 minutes of use with an 80% charged battery. Turning it back on worked for about a minute, then shut off again. Two or three more off-on cycles, each shorter than the last, then it wouldn't come back on at all for several minutes. Reading from ebike forums I decided the display was the likely culprit so I put the battery in the 1200 bike but it misbehaved in exactly the same way. Thinking I might have a bad cell group I checked the partially discharged battery voltage at the bms 13s connector. There was either a 3.69 or 3.70 reading between each post with 48.1 volts overall read at the battery case contacts. I charged the battery up and got a reading of 4.19 or 4.20 between the posts and 54.6 overall. The bike ran a little longer with a full charge but misbehaved the same way after about 10 minutes. So I ordered a new bms and soldered it in. Hit the power button and the LCD lit up just as it should. Went for a ride, but within 10 minutes, same misbehavior.

    Since it works when cold and gets progressively and quickly worse with use I'm thinking heat from resistance at a bad connection or cell is causing it. If I could set the opened battery on my bench and put a simulated load on it I might be able to find something. Can anyone suggest a way to put a simulated load on a 48v battery? Or suggest an avenue of investigation I haven't mentioned?

    I haven't considered any component other than the battery since that's the only common component and for two bikes to fail in exactly the same way, on the same day, after one and two years respectively of perfect service is statistically highly improbable unless it is the common component.
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