SparkFun Forums

[Hydromea]

Hi,

I'm working on a small project, contains lots of LEDs, high current requirements. It needs to be battery powered. Therefore, my batteries need a high mAh. However, I'm constrained for space, so the Sparkfun 1000 mAh or higher batteries are too large. However, I was wondering if I could combine multiple smaller Li-Ion batteries in parallel to increase the overall mAh? If so, how could I go about doing that? What about the built-in protection circuity in each battery? I assume I can do this because the Sparkfun 6 Ah (https://www.sparkfun.com/products/8484) battery consists of 3 2000 mAh batteries.

Also, could I charge this hacked-together multi-cell battery with a standard lithium ion charger, like https://www.sparkfun.com/products/10217 ?
In my project I'm using a custom PCB, so I'm actually just using an MCP73831T.

Any other quirks I should be prepared for?

Thanks!

[chartle]

Not an expert but

the description for the 6 aH has this.

These three cells have been match for internal impedance and can be fully charged and discharged in parallel.

Almost every other multi cell li po battery pack has a multipin plug that breaks out the individual cells so they can be charged individually.

[Kamiquasi]

I'm also not an expert, but...

Almost every other multi cell li po battery pack has a multipin plug that breaks out the individual cells so they can be charged individually.

...those are battery packs with cells in series, which is a far more tricky affair to charge from the poles (in essence: don't.) and are thus charged in parallel with a balancing charger that makes sure they all play along nicely and has relative potential differences to suit each cell.

Hooking individual cells up in parallel is not really that big of a deal, though I would stick to the old disclaimers you'd find in regular battery-powered devices: don't mix cell types and brand; that's where that 'matched impedance' tends to come in. E.g. order 3 of the same cell, give 'm a quick test, make sure you don't have 2 that are nearly empty and 1 nearly full (with that one quickly trying to 'charge' the other two) but rather at similar levels, throw 'm in parallel, and off you go.

To the OP: charging with that product shouldn't be an issue, other than that it might be a tad slow. 500mA is nothing to snuff at, of course, but 1A charging solutions are becoming rather common. SFE carry one that comes in a shiny box: https://www.sparkfun.com/products/8293

[chartle]

Ah yes parallel vs serial connection.

Just wondering if just buying the same battery from the same manufacturer is enough and they may be have to be matched a little better.

Also I'm not sure how the individual protection circuits could mess up the output. What happens when one battery cuts out before the others?