charging batteries

Other Hardware Motors, Mechanics, Power and CNC
1

dear anyone,

Am I right if i state this:

If I make a brand new battery pack with 3 cells in series (3S)
I am able to charge them at a voltage of 12.6 volts with a board such as this one:

but the board deactivates the battery charging as soon as one of the cells reached 4.2 volts.
and also deactivates the batteries when one is under 2.3 volts.
but it doesn't charge all of the to 4.2V only 1 so one can be at 3.8V when the other is at 4.2V
(This shouldn't be a problem if you bought them new but after charging the all a few times differences may occur.)

so far so good right?

okay here it comes:
If I disconnect all the cells from their sockets when the difference gets to big and than charge them all with a 1S charger such as this one:
http://www.ebay.com/itm/USB-5V-1A-1S-3-7V-Li-ion-Lithium-18650-Battery-Charging-Module-Charger-Board-/172451426542?var=&hash=item2826e7f0ee:m:mPRLwz0nWfXKyYNqIyta1-A
all at the same time they should all reach 4.2 volts because they are charged separately.

If I put the cells back into the 3S formation the should be "reset" so to say.
now they all discharge and reach 2.3 volts at approximately the same time and when charged 4.2V at approximately the same time.

Right? I'm not so sure but almost sure just asking someone with more experience than me to help me...

yours faithfully,
-Maarten

2

but the board deactivates the battery charging as soon as one of the cells reached 4.2 volts.
and also deactivates the batteries when one is under 2.3 volts.

I can't see where the ebay description says this, but it sounds reasonable from what it does say on the page.

This seems an unusual system. Mostly you would use a "balancing" BMS which would shunt current around the high cell until all cells come up to the desired voltage.

Charging in parallel or separately then assembling a series battery from those cells is one way to get around the balancing problem. It can be a hassle but I have built a relay module in the past which does this, so I could run at 48V and charge at 12V.

3

okay thanks,

I just wanted to know if it was safe to charge them separately and then put them back to the BMS

just because i know the BMS charges until one cell reached 4.2V and stops giving power if one cell reaches 2.3V.
if the difference gets to big like 1V difference between 2 cells you lose a lot of power.
if I than charged them all the way up again and put back together it should work as you say.

Thanks!

  • Maarten