Battery draining quickly

Hi I have a 12s4p 21700 P42A pack. I rode ~50 km range the last Friday. My battery draind down to 36.7 volts (3.06v/cell) acording to Focbox UI. Today when I ride the board I got shitty range

My BMS is due to be replaced as son i recive My new one eventually. It is wired to Charge only. I don’t know a lot about batteries and wonder what can be at wrong.

Before I started my ride today I charged it full 50.0v acording to Focbox UI app.

My charger is a YzPower 12s(50.4v) 6A charger.
Never had this problem before. I have like 20-30 charges only on this battery never had the battery below 40v before the last ride.

Any ideas?

Edit I have checked before that my battery is att 50.4 volt with a multimeter. And my charger charges att 50.4v.

Let it charge more? I noticed mine drops like 1v after charging, then it does one more small round of charging and it stays at 50.4v after that, then it is really charged.
Also make sure all cells are balanced

My charger was plugged in 1.5 hours after it was fully charged.

So open Upp THE battery and take individual voltage checks? Or just the p groups.?

Are those the cells I welded the p groups?

Can you measure each p group voltage and check?
No need to measure each cell, because it will show the parralel group voltage together

Yes it is. I will. As soon as I get home.

I rode another 2.5km and the voltage is at 44.6v. (14wh/km)

The voltage drops slower know? Is it a indikation that it’s a p-group that is spooky?

if one p group is lower than the others, that means something is wrong about it, if the pack if low cycles it can be replaced

Kepp the battery plugged in to the charger for longer, considering bms is only probably 50ma balance, and you have a 16ah battery it takes some time to balance out hopefully

The first p-group is dead shows no voltage.

All other shows simular voltage. 4.06-4.07 total voltage 44.8 volts. So I just need to replace it right?.

Or can I run it at 11S but I’ll need a 11s BMS and a 11s charger right?

Just remove it from the pack, and use the battery as 11s if you must, you should still be able to charge it with a 12s charger safely as bms will cutoff at 4.2v anyways.

How many cycles does the battery have?

I guess 20 charges max 500km. Never riden below 40 total volt. Except the latest time.

I guess a new p group shuld fix the problem and stay in balance with the rest of the pack.
Weird that only one group died though, a few days ago i eptied my 12s4p 40t pack to 2.6v per cell and it charged right back up…

Yeah until I get the new cells can I use the board as is? Or should I remove the dead p group right away. I don’t have a 11s charger can I use my 12s to charge my to be 11s battery.?

Well it would be better if you didnt, because then there would be an even more difference between the new and old p groups

1 Like