Charging battery in parallel

Hi guys, I'm prettey new to the forum and to the recycling battery world. Watching video around Youtube I see lot of people consider safe charging battery in parallel without any "protection". Than I read some article that said to absolute avoid to charge battery in parallel.

Can someone explain me this? Is it safe or not? What should I consider?

Charging battery in parallel is no problem as such as long as its done in a safe way. Make sure you are within limits such as

* Voltage
* Temperature
* Max current per cell (This depends on the IR so dont htink its even among the cells...)
* And more factors for sure.

After you have tested the cells you have a certain set of cells that should be close enough to work in parallel.

If you look at industrial systems or prebuilt you will see that everyone of them have cells in parallel to boost the total capacity. Its nothing weird!
For instance valence 12V pack can be 4s100p from the start

What you SHOULD NOT do is to mix unknown cells and start abusing them! That will lead to issues. Thats generally why many people state you should not do it.

Thats my 5 cents doing parallel charging on Lithium for more than 10 years

What should you consider ~


When charging in parallel as daromer said cells of approximately the same voltage range can be put into a parallel charging system.
i.e. say .05v to .09v. I personally would not have a deviation of more than .04 volts at that low voltage and then charge to 1V at 50mA for a day or so. Then slowly increase voltage and amperage till it is acceptable to go into a single cell charger.
As the voltage increases the deviation between voltages should be much lower 2.8v to 3V as now there is some amperage and voltage potential between the cells and will cause cells to try to equalize at a rapid pace which can cause a problem. I have built a 20 cell charging board with each of the individual cell holders fused with a thin fuse wire. I was charging low voltage cells and inadvertently inserted a much higher voltage cell and I had an Edison light bulb for a second or 2. Had the fuse wire not been there I am not sure what would have happened but I am sure it would not have been good.
If you are parallel charging 3.7 or so cells I would keep them very close to the same voltage. Hence I believe most of us (I may be wrong) at that voltage charge each cell independent to 4.2 for testing


IMHO that is what you should consider.

Wolf