calling the electrical savy, battery charging

[actionstan]

Hello all,

Quick question, my child has 2 remote control cars they both take a similar 9.6v battery pack. The difference is.. one is a nickel-cadmium and the other is lithium ion. The issue is that the charger for the lithium ion took a dump. Am I safe to use the charger that came with the nickel cadmium battery? It is the same voltage but the out put is slightly lower. To me it should be safe, but just take longer to charge. Let me know your thoughts, thanks!

 

[JHZR2]

Li-ion will explode if abused. Abuse can occur from overcharge, overdischarge, high temperature, ripple and other effects. Short curcuits inside Li-ion cause a substantial amount of gassing and then explosion, including thermite reactions if the materials are correct. Most Li-ion cells use a metal oxide cathode that will self-generate oxygen when decomposing. There is enough energy in a small 18650 cell to take it over 800C.

So be very careful.

Yes, in the lab, we can do CC/CV and other charging profiles where we have control of the current limits, the charge profile, and the cutouts to prevent abuse. My greatest issue is that you have zero control over what kind of charge profile and controls are in there.

If it were NiMh and NiCd I wouldnt be that concerned, since they are both 1.2V-ish cells with similar chemistry. Li-ion is a 3.6-ish V cell (varies with cathode chemistry), with a max charge voltge for most oxide cathodes of around 4.1V. So there is no integer value that would align between the NiCd topping voltage and the Li-ion. This would cause either an undercharge or an overcharge, depending upon how the chargers deal with the potentials.

Now, the Li-ion cells could have an internal circuit to effect interface voltage for commonality... And then things would be different again, but then you are introducing more variables.

Personally, going in blind, Id say no. But with some pictures of the battery and charger specs, and perhaps a close watch on the charge voltage with a multimeter, you may be able to finagle it. Charge rate (current) is also important here...

 

[spackard]

No, you're not safe. If you were, you wouldn't be asking.

 

[actionstan]

Fair enough, looks like it's time to find a new charger, thx guys!

 

[Donald]

Originally Posted By: actionstan
Hello all,

Quick question, my child has 2 remote control cars they both take a similar 9.6v battery pack. The difference is.. one is a nickel-cadmium and the other is lithium ion. The issue is that the charger for the lithium ion took a dump. Am I safe to use the charger that came with the nickel cadmium battery? It is the same voltage but the out put is slightly lower. To me it should be safe, but just take longer to charge. Let me know your thoughts, thanks!


NO. Get the correct charger. The LiIon can probably do both chemistries, but not the other way around.

 

[turbodieselfreak]

Absolutely NOT. If you want to learn just how dangerous lithium ion batteries can get with misuse, visit candlepowerforums. It's the BITOG of flashlights and batteries. They even have a subforum for this topic entitled "smoke and fire".