I just got a duct tape 36v 10ah battery from "mp3hk" on ebay - I knew it's not Ping but I only need to ride short distances so I thought I'd give it a gamble. However the battery is extremely unbalanced and not sure if this is normal for a new pack.
The battery arrived in one piece and performed well on a test ride, but the charger blew up only the second time I plugged it in.
I bought a SLA charger until I can get a new lithium charger. After charging a half time with the now blown up lithium charger, and a full charge with the SLA, I ran out of power after riding only 6km.
I took the pack apart and found several loose welds, which I carefully fixed using stainless steel flux and solder.
However, my range is still only 6km.
I measured the voltage of each cell group within the battery, and got a pretty big variation.
After a full charge, the highest cell in the group was 3.90v (which is probably the BMS cutoff), and the lowest cell was 3.1V! This explains my poor range. Once this lowest group discharges to 2.0v, the BMS cuts off all power.
I'm still waiting for my Lifepo4 charger to arrive and am still charging with the SLA charger.
I know the non-Ping sellers of duct tape batteries are a gamble, but it's not normal for a new pack to be this far out of balance, is it??
Will it be possible to bring the pack back into balance when my Lifepo4 charger arrives? The SLA pack is only charging at 43.2v. The new Lifepo4 charger should charge at 45v.