Li-Po battery charger

[VictorPS]

I like to build a charger to quick charge a Li-po 4.2V 550mAH battery, it is for my mini helicopter.
Question:
1. What is the max initial constant cuurent allow?
2. What is the max/recomended constant voltage later on?
3. Will it damage the battery if leave it on constant voltage mode?

Thank you,

 

[dknguyen]

Charge

You might be better off asking that question on an RC forum because those guys are fanatic about their batteries and know the details very very well.. The only thing I really know about LiPo is that you absolutely cannot let it exceed 4.2V. To fully charge a LiPo you need to get it as close to 4.2V as possible without exeed it. With store-bought chargers they have to ocassionally get recalibrated to ensure that they can fully charge the LiPo without overcharging it. Any voltage about 4.2V no matter how small will caues the LiPo to start getting puffy.

 

[VictorPS]

Is the Li-Po charge charateristic same with Li-ion?

 

[Papabravo]

Not knowing any better I found the following link amusing

http://www.poetrystore.com/lipo.html

This link is on point however

http://www.rchobbies.org/lithium_battery_breakthrough.htm

 

[dknguyen]

Bet not.

Is the Li-Po charge charateristic same with Li-ion?

My instinct is that they are most definately not because one is low current and one is a high current type battery and they are completely different kinds of batteries also. Just because they both contain Lithium doesn't mean they are similar. (ALthough that is somewhat true with NiCds and NiMH).

Out of Pb-Acid, NiCd, NiMH, Li-Ion, and Li-Poly that Li-Poly is the type with the strictest charging requirements and the one that is most easily damaged from mischarging.

 

[hjames]

Take a gander at page 13 of **broken link removed**
(single chip battery charger chip by Texas Inst.)

Pretty much any of the big chip companies has their Li battery charging chip - Linear Tech and Texas Inst. are probably have the most variety though.

But for the short answers:
1) if in deep discharge(i.e. < 3V), <1/10C, otherwise usually ~1C (i.e. 550mA)
2)4.2V at ~1%, the closer the better. 5% resistors in this circuit would be a bad thing...
3) no, that will overcharge the battery and damage it. Stop charging when charging current has fallen below 1/10C