Lithium batts and voltage question

Armored Cars

Two questions:

Can lithium batts be charged on standard chargers?

For regulating voltage are there any advantages to using voltage regulators instead of resistors?
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Chris Savage

Do you mean Lithium Ion?· I myself have never heard of Rechargable Lithium Batteries!· Every Lithium Battery I have ever used would explode if you attempted to recharge it.· You would normally use L-Ion, Lead-Acid, NiCad or NiMH Batteries.· And as for Lithium Ion batteries using a standard charger, I don't believe so, since even NiCad and NiMH Batteries have different charging requirements, and they are radically different from Lion.· Lead-Acid Batteries are also different in their charging characteristics.





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Chris Savage

Knight Designs
324 West Main Street
P.O. Box 97
Montour Falls, NY 14865
(607) 535-6777

Business Page:·· http://www.knightdesigns.com
Personal Page:··· http://www.lightlink.com/dream/chris
Designs Page:··· http://www.lightlink.com/dream/designs
·

Dave Paton

First an extremely emphatic warning:

Regular Lithiums are NOT rechargable. Lithium Ion and Lithium Polymer batteries are indeed rechargable, but if you use a regular charger there is a very good likelihood that the cells will explode violently and can set anything within a 2' radius on fire.

Li-Ion and Li-Poly cells need to be charged in a very specific way, with very well defined charge termination conditions to prevent the overcharging that leads very quickly to expensive and painful results. There are a ton of Li- compatible chargers available these days, and lots of good sources for the prismatic and rolled cells.

There is nothing to fear from Li-Ion cells when using a Li-Ion rated charger. They offer superior charge density, high discharge rates, and absolutely no memory effects at all. However, like any high performance iitem (Indy car, fine camera, large telescope) there are specific limits to their application and care that must be obeyed.

Personally, I use them in my electric plane, my RC boat, as well as in my robots. They absolutely stomp all over lead acid cells for power density. They clobber NiCad for memory immunity. They beat NiMH for recharge cycle length. I recommend them to everyone. They rock. Just be careful.

As for regulation:
Resistors drop a voltage that is proportional with thhe current through them. If your load is variable, the voltage to that load will also vary. Regulators offer a real live fixed output voltage. For LEDs and other constant current devices, resistors are fine. For circuits composed of ICs, use a real regulator.

-dave

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Post Edited (Dave Paton) : 10/28/2004 1:54:07 PM GMT

LoopyByteloose

I really like them.· I got one with my electric r/c airplane and found the 7.2 volts perfect for using Stamps with a 7805 regulator supporting peripherals.· I bought a second one and was using it when it swelled up like a pregnant guppy and would not hold a charge.

After a little research I tossed it out.· They do explode!· The packaging does have a relief point to try to minimize the POW.· But, you really have to let go of them when they get fat.· I only used the second one for a month or so and I couldn't return it.

Nevertheless, who wants the shock, the damage, and whatever.


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G. Herzog in Taiwan

Dave Paton

Mis-charging them does that. First the overcharge kills the chemical balance in the cell, killing it's rechargability, then it unbalabces it so much the chemicals overheat and flashover occurs. You're lucky your swollen pack didn't pop on you. Out of curiosity, how were you charging them? If the series cells (7.4V packs are two cells in series) become unbalanced for any reason, one will overhcarge before the other. Mine are set up so they charge in parallel, but run in series.

-dave

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This is not a sig. This is a duck. Quack.