Calculating Charge Amps

Evening all.

Can someone please point me in the right direction to calculate max charge amps for a quick pack i put together.

I have 4 18650 cells, connected in paralel, then those connected x3 to make my 3S "12v" battery pack.

I have added the wiring for Balance charging also. This all works fine. What im needing to work out, is what charge rate to use.

I have a PowerPal Etronix charger that maxes out at 6A on Balance Lithium mode.

The cells are recycled :

Sony
US18650GR
2100mAh (Stated).

Cheers!

Kev

You must look at the stats of the cells and go with the lowest in the pack(s).
The cells datasheet will state what the max charge current is. You don't want to go over the lowest cell times the number of cells in parallel

However, since most of us are using reclaimed cells, it's a lot lower than the C rating. Most of us use 500mA as the max.

So our base charging current of about 500mA per cell, in an 80p pack, that'd be 40A max.

Now, for every string in parallel you have, you can effectively add that to the base. Like with Pete, he can handle 1000A charging current or more if his chargers could output that high of current. I think he has 5 strings in parallel if I remember correctly. On a live stream awhile back, I think he broke the 1000A barrier for a brief time.

So like Korishan says, you have 4p cells, so it's 500mA/cell max x4 ie = 2A for your pack, if your cells are OK. If weaker or <2V/cell then use less.

Thanks all

2A was about where I was at anyway.

Sorry to ask again, but if i have 12 cells in my pack, which i do, doesnt that mean i can put 500ma x 12 or is it 500 ma x 3 (as the cells are in parallel groups of 4, and there are 3 of them ?)

500ma x 12 = 6 amp?

Cheers

Being 4p I would charge at 4 A, 1A per cell, no matter if you charge the 4p alone or the whole pack, 4A is your current, charging the whole pack you will charge at +-12V*4A= 48W, charging separately will be +-4V*4A=12W.

So don't put more than one Amp per cell in paralel, series only multiply the voltage not the amperage.

Anyway check datasheet of the cells to get the maximum charging current. There are few variants ofUS18650GR, evenwith larger capacity recommends 1Acharging current and 500 mAh discharging.

Regards

The FAQ discusses parallel vs series and the difference between 3s4p vs 4p3s plus loads of other simple questions answered