Hi. I built a 32Ahr USB power bank using 8p5s li-ion cells. I have a active balancer i can switch on/off and also a BMS (BM3451 TNDC T20B). All cells were carefully matched and pretty well balanced. I have an issue where a over charge event occurs but once the charger is removed, the bms doesnt fully switch back on, i have roughly 0.6v@1A and some resistance that isnt 0 ohms.. now i had the same issue with another bms but i could unplug that, this one is soldered in and besides removing the lid to reset is a pain.. before fitting this bms i tested it on 1p5s battery pack to find its upper/lower limit and it worked just fine but i was charging/discharging it with 1A. In the usb power bank, once its charged and triggered, the usb outputs detect an issue preventing me discharging the pack. Is this because of the overcharge hysteresis? Is there a better ic with a narrower upper switching?
Picture of usb power bank (with old BMS) and the replacemfnt BMS, both cheap ebay jobs