battery charge

[robdon]

thanks for you help Dave, as soon as I get a full day without grand kids etc.
I will give it a go , and come back, with results.
thanks again
ROB

 

[robdon]

I am at this moment charging individual cells with the 5v mobile charger,
the one I have charges at 1 amp, I have another that charges at 2 amp,
would that be better or stay at 1 amp for safety.
taking a long time over an hour for one cell, from 3.8v to 4.0v
how long does it normally take say to charge .3 of a volt.
ROB

 

[Alan Quay]

From 3.8 to 4v is around 20%. Assuming you have a 10ah cell, then you need to get 2ah into it, which will take 2 hours at 1 amp, or 1 hour at 2 amps (give or take)

Thats why I suggested bringing the two high cells down, rather than the 8 remaining cells up.

 

[Deleted member 4366]

Charging at 2 amps will be OK. The 38v cells are probably about 1/3 the way down, so would need about 5aH to charge: 2 1/2 hrs at 2 amps.

Don't forget that it'll accelerate as it approaches 4.2v.

 

[robdon]

ok I will try 2amps, at the moment going fine, should get finished by morning.
when I get them to 4.1v each, do I charge the battery
ROB

 

[robdon]

After a ,day and a half, this is as far as I have got, measuring from the red wire, on the BMS ribbon cable
1. 4.1 volt.
2. 4.0 volt
3. 4.0 volt
4. 4.03 volt
5. 4.18 volt
6. 4.16 volt
7. 4.0 volt
8. 4.0 volt
9. 4.0 volt
10. 4.0 volt.
I can get them all to 4.1 volt but when I take the usb 5.0 volt charger off they drop back to 4.0 v or 3.99 v, have tried a few times they drop back,
will I try the 36 volt charger now, last night the battery volts measured at base battery was 40.5 volts.
ROB

 

[Deleted member 4366]

You should use it now, then see what you get after the next charge. The 4.18v cell will trip the BMS as soon as you start to charge, so no point in putting on the charger. After a couple of charge/discharge cycles, the bleed resistors should do the rest.

 

[robdon]

sorry I have done this before you replied, jumping the gun.
put it on charge run for about 15 mins, then stopped turned to green .
Checked battery volts 40.8 volts.
ROB

 

[Deleted member 4366]

If you want to go higher, you'd have to drain those two high cells down.

 

[robdon]

do I do that through the BMS ribbon cable with a bulb, and if so what size bulb, or any thing else required.
thanks for all your help
ROB