diffrence between a Nimh charger & a Lipo charger

[harrys]

Hi there

I just wanted t know the difference between a ordinary NIMH charger & a Lipo Charger... any one technical can help me out.. i need to understand this in detail... I have just ordered a set of Lipo batteries...

harry.

[Kiva Flyer]

NiMh peak chargers will terminate charge when they detect a voltage peak. LiPo chargers monitor voltage and taper current off as a predetermined voltage limit is reached. LiPos don't peak, so if you charge them on a peak charger, they will just continue to charge until they "vent with flames".

[TheTank]

Its time to order a charger that is made to charge Lipos. depending on the packs you ordered, you can get a charger for less than 50 bucks that will charge nicads, nimhs, and Li-ions/Li-pos.

[gareth.ky]

Lipos, in fact all lithium chemistries charge in 2 phases. The first phases is constant current of 1C. Thats 1 x the current rating of the pack aka its capacity in mah. So a 2100mah pack will charge at 2.1 amps. Charge above this current will damage the packs and cause "venting with flames" unless the battery is rated otherwise. When the charger detects that the cell has reached 3.6v it is about 80% charged and it switches into phase 2 which is constant voltage. The charger slowly decreases the current, constantly monitoring the voltage and maintaining it at 3.6v. As the pack finishes charging less and less current is required to maintain the pack at 3.6v. Finally so little current is required that the charger shuts off.

I'm sure you re aware that you shouldn't charge LiPo packs in NiMh mode or with a NiMh peak charger. They don't do 2 phase charging.

[ryan_m]

actually the max voltage on a lipo cell is 4.2v/cell, not 3.6. A 3s pack should have a nominal voltage of 12.6 volts when fully charged. Otherwise Gareth.ky is exactly right, the charger will get the pack up to full voltage, and then maintain it there with ever decreasing current until it's fully charged up.

[gareth.ky]

sorry, he's right, its 4.2v

[Edge 540]

Not sure if I agree with the 1c theory. It doesn't know what 1c is. I usually charge my lipos at much less. Example 2100 charge at 1A. 350 at 150mah. It's not going to just pump 2.1A or .35A in until they reach 80%...
It charges at the pre determined max allowed current.

[harrys]

I have even heard people use their computer power supply to charge batteries... is there any site which tells you make a lipo charger ... just wanted to know.

[eblenkle]

	Quote: Originally Posted by harrys
	I have even heard people use their computer power supply to charge batteries... is there any site which tells you make a lipo charger ... just wanted to know.

Good Morning Harry

I think you may have a little misunderstading regarding the computer power supply. People are using the 12 volts from a computer power supply to provide the 12 volts at about 10 amps to drive the LIPO chargers. the Frankenpower article by Mike Bargman in the electrics section of the forum describes how to convert a computer power supply to a source for the LIPO charger.

I think this is the link to that forum
http://www.flyinggiants.com/forums/f...er-supply.html


Best Regards
Ernie

[harrys]

Hi Ernie

thanks a lot for that link...