repair / testing a failed mobility scooter battery pack

[carpetpaul]

Hi guys, I wonder if you can help. My friend has asked me to have a look at his mums mobility scooter battery pack. obviously she'll have to buy a new one if we can't repair it, but they want silly money for a new one, so I thought it would be worth having a look, I was hoping to find one or two dad cells, but it wasn't the case. It's mad with Panasonic NCR cells, and so far, they're testing matching voltages and good capacity. she's reporting that, during use, the battery gauge on the dashboard depletes rapidly, and she's worried out becoming stranded.
Being a complete dumb-ass, I did't ask for the charger, so I wouldn't know if that was the issue, and it's completely disassembled now. I guess this is the unanswerable question, but I don't have much of a choice now, other than complete the capacity testing, then reassemble it again and test the charger.
I've made packs for my Ebike before now, so I guess I could buy a cheap Chinese BMS, and have an attempt at replacing the electronics in the pack. how would I know how many Amps of max output I would need for it ?

 

[italianuser]

Yes, I'd say you need the charger to do a good test. You say the cells seem good, are you also able to check the IR value of the cells? I'd also do a full CDC charge-discharge-charge cycle on some cells to see how they react. I mean, if it's not the cells then next in line is the BMS.

About the Amps I don't know anything about mobility scooters, I suppose it should be written somewhere on the pack or on the manual; maybe there's a make-model on the BMS? Last attempt I'd check out the producers website searching for replacement batteries, you should find the specs there. Or maybe give him a ring (and don't tell him you're taking the battery to pieces!).

 

[carpetpaul]

thanks for your reply. I've been using Litocala Lil500 tester/chargers, so I've done the charge/discharge test, and they all match bar for a couple of outliers with only around 10% capacity difference. I don't have a proper resistance tester, but the charger itself gives a rough indication, and there are no unusual differences.
For the spec of the BMS, I can't find anything online regarding any replacement parts, or the spec of this board, but when I made batteries for my electric bicycle, a rough guess produced results that worked fine, I imagine that it's cheap to but the parts, although, I have to admit, the output cables to the power connected are far chunkier than what was used on my electric bike, however this is at a lower voltage, so perhaps that's part of the reason