Battery Charges - Nicad vs Li

[Knottscott]

My understanding is that the Li batteries require a different charger than the Nicads, and that you can't substitute the Nicad charger for the Li charger. My question is what's happening that makes them non-compatible, and are there any mods that I can make to a Nicad charger to make it compatible?

I've currently got the Ryobi made CMan C3 19.2 v batteries and charger and would like to pick up the Li battery, but the Li charger ups the cost quite a bit.

Got this:


Want this:


TIA!

[LCHIEN]

not easy mods, the fast chargers all have some strategy programmed into them to make them shut off charging at the right point else overcharging at a high rate can damage the battery. Nicads and NiMH use rate of temperature rise feedback, not sure offhand what is used for LI but I know its different.

[Knottscott]

I was afraid of that. I also knew I could count on you for a good explanation!

Sounds like a sale price is a better option than a mod! Thanks...

[MikeMcCoy]

It doesn't solve your problem but that's why I bought the Milwaukee multi bay charger. It does all of the Milwaukee batteries.

[sscherin]

Li Batteries are a little more picky..
If you over Charge them they have a habit of catching on fire.. Not good..
If you charge them to fast.. same thing..

The Charging voltages may not be the same either.

The 19.2v Nimh pack has 16 1.2v cells in it..

LiIon cells are 3.7v each so they are either using a 5 cell 18.5v pack or a 6 cell 22.2 v pack

If it's a 22.2 v 6 cell pack the old NiMh charger will never fully charge the LiIon pack.

If as they claim you will get more performance with the LiIon pack them I'm sure it's just a 22.2v pack with a 19.2v sticker.

May of the Power tool packs use (or used to) Molicell's
http://www.molienergy.com/products.htm

I almost forgot..

Charging Methods

Peak or Delta peak

This is the method used to detect the end of a charging cycle in Ni-Mh and Ni-Cd chemestry. It mesures the voltage of the charging pack. A typical curve will start rising fast, to gradually slow down and finally start to drop. The charger will detect a drop ranging from 5mv for Ni-Mh to 10mv fo Ni-Cd. It will then terminate the charging process.

CC-CV

This is the method used to charge Lithium packs. It first forces constant current in the pack until the voltage rise up to the "normal" level (7.4v for a 2 cells pack or 11.1v for a 3 cells pack). The charger will then only apply constant voltage to the pack and let it take whatever current it needs. The charge will finish when almost no current is drained into the pack.

Next bit thing in batteries. Lithium Manganese
Higher Discharge rates then LiPoly and lower risk of a Runaway Thermal event (fire!!)
Same Chargers as Li-poly so no big change there.