I understand everything on the surface.

But I'm wondering if I have two lipos and connect them in parallel to increase capacity of my pack, wont there be sparks when I initially connect them? Isn't there going to be a large current flow regulated only by the internal resistance of the batteries?

So if one is like 4.2V and the other is 4, couldn't the discharge current of one and the charge current of the other, exceed their specs?

Do I need to charge both as close to the same as possible to reduce this?

Any best practices when assembling the pack?

Do they self balance and can I charge them just as if I was charging one alone?

 

Don't forget that lithium battery packs already have cells in parallel, that's what the "P" figure means in 4S2P.
So, before you connect them the first time, make sure that they are both fully charged, otherwise one will charge the other and quite a lot of current might flow.
Then you can charge them as one pack.

 

Thanks for your reply! I know it's commonly done, just wanted to make sure I Wasn't missing anything and that I used best practices when doing this.

Thanks a bunch!

 

For safety reasons I should have mentioned that to wire them in parallel they should both be the same spec, preferably same manufacturer.

 

I wouldn’t try it, but I doubt that sparks would fly connecting two batteries at 4.0 and 4.2V unless the were very high in capacity (like 10s of Ah) There is actually very little difference in state of charge between those two voltages.

A fully changed LiIon cell drops to 4.0V very quickly, then levels out at around 3.7V for most of its charge cycle.

As others have said, only connect them when the voltages are equal, and you will not have to worry.

 

Don't forget that lithium battery packs already have cells in parallel, that's what the "P" figure means in 4S2P.
So, before you connect them the first time, make sure that they are both fully charged, otherwise one will charge the other and quite a lot of current might flow.
Then you can charge them as one pack.

Normally, I parallel them at first using a Low value Resistor for a while to "Equalise" the voltage and then Parallel them directly. Just a precaution followed from the LA battery days.

 

I wouldn’t try it, but I doubt that sparks would fly connecting two batteries at 4.0 and 4.2V unless the were very high in capacity (like 10s of Ah) There is actually very little difference in state of charge between those two voltages.

A fully changed LiIon cell drops to 4.0V very quickly, then levels out at around 3.7V for most of its charge cycle.

As others have said, only connect them when the voltages are equal, and you will not have to worry.

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@BobTPH, The TS is asking about Lipo batteries, not LiIon batteries...