Li-Ion vs. -Poly

[D Yuniskis]

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)

 

[Raveninghorde]

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)

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

 

[Adrian Jansen]

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)

Lots of useful info on batteries at:

http://batteryuniversity.com/

 

[Robert Roland]

It is my understanding that the charging technique for
LiPoly and LiIon are identical (?).

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?

 

[Raveninghorde]

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.

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

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.

LiPo and Li-ion cells are flat at about 2.5V and fully charged at
4.2V. The nominal voltage is pretty meaningless.