pcb question with more than 2 cells

[Loc]

Say I got 4 batteries, each 3.7V 5000 mAh. If I wanted 7.4V and 10,000 mAh, would I wire them to a 7.4V pcb the same way I would 2 cells? Like this picture

Only I would have an extra battery on com and B+ and an extra battery on com and B-, right?

If I wanted 6 batteries for 7.4V 15,000 mAh, would it be the same thing except 3 cells on either side? Or would I need a different pcb?

 

[Aux]

That's right. The voltage is calculated by how many consecutive batteries the current passes through... so from B+ to COM to B-, you're going through two batteries. If you put two batteries in parallel, half the current goes through each so they drain half as fast (so you effectively add the capacities), but in the end tracing a single electron in the current, it goes through one top battery and one bottom battery so your voltage is still 7.4. A 2x2 like you've proposed (or even 3x2, 4x2, and so on) works just fine. In this case the PCB is only providing you solder points and traces. Just make sure you solder each "pack" on each side with the same polarity as if it was a single battery (all positives of the top "pack" to B+, negatives to COM; all positives on the bottom to COM, all negatives to B-).

 

[Loc]

Cool, thank you very much.

So these are the batteries I'm looking at.

http://www.batteryspace.com/Polymer-Li- ... ---UN.aspx

I have enough room for 4 of them and possibly enough room for 6. From this list of pcbs, which one do I get? http://www.batteryspace.com/pcbfor72v74vpack.aspx

I see they all have different amp rates. I don't completely understand the significance of that.

 

[Prog]

I believe that generally this one is recommended.

 

[Aux]

The max discharge rate (amp rate) is how much power it can handle draining at one time. Circuits that need more power will draw more power, potentially causing harm to your batteries / protection circuit. Those batteries can supply a max of 10A each. Just like with capacity that only adds in parallel, so your 2x2 will supply a max of 20A and a 3x2, 30A. However if your circuit is drawing 20-30 amps, you may be doing something wrong. The 8A circuit Prog linked will probably do you well, unless you're doing some kind of PS3 or 360 portable.

 

[Loc]

Thanks for the help guys.