"BATTERY WON'T CHARGE" STORY
Yesterday, I commuted on the Level.2 despite it being a bit cold, hovering right around 30 °F. (-1 °C) When I got home, my battery was at 19%. I decided to plug it in. It wouldn't charge using the jack on the outside of the bike. I could've sworn I've charged it in colder temperatures than this before, so I was puzzled. I had been riding around in salt spray, so I wondered if something got shorted out or corroded. I checked and all the connections were clean and dry.
I thought maybe a connection between the battery and the outside of the bike was going bad, so I removed the battery and tried charging it directly. No dice, the light on the OEM charger wouldn't go from green to red.
I got out my multimeter and tried to check the pack voltage. Couldn't do it, the contacts are too far recessed (for safety against accidental short circuits when it's out of the bike) and I don't have needle-sharp probe tips.
Next, I plugged the charger directly into the battery pack. Same thing. I wondered if the factory charger was OK. It should be, as it has never been dropped or anything. I checked its output with my multimeter, and its output was pulsing. It's either messed up, or its a smarter charger than I thought, looking for the right voltage before allowing a charge load. I got my other charger, the adjustable output one I got from AliExpress. That one has a display, and I could see the voltage was down near zero and no current.
The BMS in the battery pack seemed to have shut down the battery output, either for high internal temperature, due to the cells discharging on the mostly uphill ride home or due to cold. (cold is more likely, I think)
I took some pictures in case I had to write to Aventon for warranty service, but I decided to bring the pack inside the house and let it warm up or cool down, then try again later. A few hours later, I plugged it in to the adjustable output charger and it charged fine. I let it go overnight at its ~52 V 0.5 A setting. In the morning, it was still charging. I loaded it into the bike and powered it on; right at 81%; perfect!
The moral of the story is that the BMS (battery management system) on a good battery pack and some charger electronics are smarter than I thought. The BMS will not only shut the pack down if it overheats, but also will let it discharge in the cold, but not charge in the cold, keeping the cells in their specified temperature range. The OEM charger from Aventon is a good one, with a 3 A output and looking for a battery load before activating the charging sequence.
Nice job on the pack BMS, Aventon, and nice job on the UL 2271 battery pack safety certification, SGS.
I'll have to check tonight if the stock charger works properly again, now that the battery is warmer in the garage. (my attached garage is about 20° warmer in the winter than outside)
