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Quad 18650 power supply

Added by pescadito about 1 month ago

Hi, your charger is realy nice,
but what about balancing the charge...?
do you forget it?
or if no, why you do not control it?

may be something like this
- http://www.ebay.com/itm/5-6-or-7-cells-20A-w-balancing-Li-ion-Lithium-18650-Battery-In-Out-Protection-/111091669495?_ul=AR
could help, but it add some extra cost

Regards, Pescadito


Replies (2)

RE: Quad 18650 power supply - Added by martynj about 1 month ago

@pescadito,

Charge balancing is incorporated, very economically. Since there is no schematic in the article, this can be worked out from reading the text - each cell when charging has its own 1Ω resistor in series and this combination is paralleled up four times to be the load presented to the USB charger module.
Now imagine if cell A somehow has more charge in than the others - this means potential A is slightly higher. This drives current out of A into the others, safely limited by the 1Ω resistor. Eventually cell A will lose this excess charge to the other cells with a slight fall in potential (and some slight rises in the potential of the others).

If another cell is now carrying an excess charge, the same balancing process (actually in parallel) occurs. These circulating currents stop when the all the cell potentials are equal - since we can assume the cell temperatures are approximately the same, this maps to approximately equal charge in each cell.
It is not a super efficient mechanism, but it works and costs only the additional series resistors.
For discharge through the load, the cells are put in series without the series resistors so no charge is wasted there.

RE: Quad 18650 power supply - Added by pescadito about 1 month ago

Hey MartynJ

Thanks for your great explanation, sorry, I'm have not a good basic electronic background.
I read it carefully and I do my schematic about it, but I'm not sure if I do it well.

Please, could you update it in the correctly way.

Regards, Pescadito.

PD
Attached file made with http://live.gnome.org/Dia

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