Li-Ion vs. -Poly

Jan 04, 2011 5 Replies
D

Hi,



One of my portable DVD players uses a (nominal) 7.4V 2600mAH Li-Poly battery. One cell appears to be toast (*loaded* voltage RAPIDLY drops from ~3.5V to ~1.8V after ~10 minutes of use; other cell holds fast at ~3.5V).



I was thinking of replacing them with a pair of 18650's as they occupy almost exactly the same space (different, though compliant, form factor; same volume -- of course!).



It is my understanding that the charging technique for LiPoly and LiIon are identical (?). I'd prefer not to have to reengineer the charger (microcontroller controlled).



[Given my druthers, I'd replace with NiCd but that would require way too much work!]

Any other pointers to watch for (besides the usual, "OMG! You can burn your house down!!")?



Thanks!



--don



P.S. pointers to a source/manufacturer of reliable *tabbed*



18650's would also be welcome. (though I may just opt to cannibalize some laptop battery packs)
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R

Yep, charging LiPo and Li-Ion is the same and so is the pack protection.

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A

Lots of useful info on batteries at:

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Regards, Adrian Jansen adrianjansen at internode dot on dot net Note reply address is invalid, convert address above to machine form.
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A

eBay. RC helicopter batteries.

Good god, why?

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R

The manual for one of my R/C chargers very explicitly states that Li-Ion batteries can not be charged with the LiPo program. My other charger has separate programs for LiPo and Li-Ion.

I know LiPo has a nominal cell voltage of 3.7V, while Li-Ion is 3.6V. I do not know if that is the only difference.

Some Li-Ion cells are marketed as "protected". I am not sure what that means, but maybe they have built-in protection against overcharge?

RoRo
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R

Both types charge in the same way. Constant current followed by a float charge at 4.2V per cell.

LiPo and Li-ion cells are flat at about 2.5V and fully charged at

4.2V. The nominal voltage is pretty meaningless.

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