Lithium Polymer Battery Charging

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taipan821
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Lithium Polymer Battery Charging

Post by taipan821 » Mon Nov 06, 2017 6:38 am

Hello all

I'm looking at a electronic project where I need to cram as much power storage into a small space as possible.
I'm looking at using Lithium polymer batteries from the remote control industry as a power source.

My issue is with charging them, as long as I ensure I balance the cells correctly, can I charge lithium polymer batteries in situ or should I remove them for charging.

Just for background info, project will include 100W led chips with an input voltage of 30V and with water cooling for heat dissipation, I figure this section of the forum has more technical knowledge of batteries
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JayceSlayn
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Re: Lithium Polymer Battery Charging

Post by JayceSlayn » Mon Nov 06, 2017 7:45 am

I would actually make sure to take a look at the lithium battery selection from BatterySpace (http://www.batteryspace.com/). I've bought from them before, they have a very wide selection of batteries in different chemistries (including multiple chemistries of lithium batteries), and they manufacture their own packs if you need something really custom.

Proper lithium battery packs will include a number of protection circuits and features on-board the pack itself, so you don't have to rely quite as much on the charger for safety, and some of the chemistries (e.g. lithium-iron-phosphate - LiFePO4) are inherently safer than others (though usually at the cost of some energy density). Most all the packs that Battery Space sells have good protection added.

And if you really want to dive deep into the care and feeding of batteries, you can also spend a few hours days reading through Battery University (http://batteryuniversity.com/learn).

From what your project sounds like: other than watching out for overheating (which a thermal fuse should help from a safety standpoint), I'd warn against cramming all the packs too tightly together. That is what has been the downfall of some recent devices: as the packs swell with charging, they build up too much pressure (or get punctured by something nearby), burst, and then catch on fire. And as always: batteries (in particular lithium batteries) have a lot of energy waiting to break out, so double/triple-check your design and fabrication to make sure everything's kosher.

EDIT: Forgot to address the actual question...you should be able to charge cells in-situ, as long as you've got good heat dissipation and space for them to swell a bit in the device. Removing them and charging them separately might be safer, but shouldn't be necessary with adequate design.
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