Battery experts, question for you guys

I am running a 12s4p 18650 pack. I am charging with a voltage protector and I don’t let it charge past 49.9 volts.

When I start charging the battery meter rises at a steady pace, maybe 1% every few minutes. But when the meter hits my max set voltage, and usually right around 90%, the chatging slows wayyyy down. Like 1% every 20-30 minutes.

Is this because I have the voltage protector set at 49.9v?

Should I just consider the board fully charged at 90% or should I just be waiting an extra 3-4 hours for that last 10%? I realize that’s a subjective question but I guess I wanna make sure it’s not forcing the batteries to charge beyond 90% if I shouldn’t be, if that makes sense.

use volts not % 12s battery full charge at 4.2v is 50.4volts at 4.1( studies saydouble life span) its 49.2

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I guess it hits constant voltage phase so current goes down… this is normal.

What ‘voltage protector’ do u use?


Okay so basically harge it to 49.2 and call it a day

I guess u dont use bms, right? In that case it would go and balance cells at that level.

But yeh i guess u saturate battery quickly and it moves in its last charging stage, thats why its so slow at end…

Do u see amps also? At which level u start?

IMG_20180618_114455 Costs 10usd and lets see amperage / wattage / time / charged capacity

I believe I’m charging at 3 amps. I use a d596 80A bestech BMS

My bms for another project doesn’t balance until the very end, so restricting the max voltage meant it wouldnt ever balance the cells, so i had get rid of the voltage limiter and charge to 100% Im not sure how other BMSs behave, maybe the point at which it balances it settable.


Interesting. How do I tell if my cells are getting balanced at the end or not?

i meaured p group in mine directly, and waited till i had different shrink, or just wrap with kapton (traps heat tho) meantime.

Says on there battery has to be fully charged to balance, is that yours?

Yes. So what I set my voltage protector at? The guy who built my battery said don’t go over 50v

I only have experience with one BMS, and it terminates the charge once balancing has complete. If you connect a multimeter inline in current mode you will see what the BMS is doing. I charge my cells with a simple cc/cv pcb. Its set to the maximum voltage of my pack. 4.2 x number of cells.

I wanted to charge to 90% only, but id have lost the BMS balance function. So scrapped that idea.

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I’m not sure why the person you bought it from told you this, but it is not correct (unless he meant to say 50.4V and not 50V). You need to charge all the way to 50.4V for the balancing to work on that BMS.