Build your own Li-Ion charger!!

segasonicfan · Post by **segasonicfan** » Fri Sep 02, 2005 11:50 am

Hey, for anyone out there that uses li-ion cells in their portables (like me) I found a GREAT way to build your own chargers: http://www.flyelectric.ukgateway.net/li-circ4.pdf

I just finished building one of these for a 3 cell charge and it works perfectly. You can get the IC from Mouser for dirt cheap and the charger is adjustable so you can charge just about ANY Li-Ion pack with it!!

-Segasonicfan

Post by **gannon** » Fri Sep 02, 2005 12:02 pm

IIRC you can build a somewhat cheap li-ion charger from just a transistor and a resistor. Not the best but it charges.

segasonicfan · Post by **segasonicfan** » Fri Sep 02, 2005 3:58 pm

well you gotta be very careful charging li-ion batteries. The method you mentioned probably damages the cells. They are far more sensitive than NIMH and such. That's why the link I posted is such a great solution. It's a safe and powerful li-ion charger that can be built for less than $15. When you spend as much money on batteries as li-ion cells cost you want to make sure they're charged properly.

-Segasonicfan

Reaperman@home · Post by **Reaperman@home** » Fri Sep 02, 2005 4:34 pm

I've always wondered:

[probably stupid question:]
Can a Lithium Ion charger charge a Lithium Polymer pack? are they the same charger?
[/probably stupid question]

LiPos are magical and frightening to me for some reason
...probably the explosions when they're charged/discharged incorrectly...

segasonicfan · Post by **segasonicfan** » Fri Sep 02, 2005 4:39 pm

Yes, they can be charged with the same charger. I'm not too clear on the differences between Li-Ion and Li-Poly but according to the home page of the link here you can use either li-poly or li-ion packs for the charger:
http://www.flyelectric.ukgateway.net/lithium.htm

I only have a couple of the same li-poly batteries and they never exploded on me...although they did puff up like a baloon when they were overcharged which I always found interesting. I popped one of them to see what would happen and a horrible smelling chemical air came out.

I think Li-poly are fundamentaly the same as li-ion but just with increased power/weight ratio. My Li-Poly packs are remarkable small for 3.6v @ 6amps.

-Segasonicfan

Reaperman@home · Post by **Reaperman@home** » Fri Sep 02, 2005 4:51 pm

if you puff them, they're about to explode. The puff both when overcharged and when discharged below a certain voltage. That's why there's generally an LED indicator on them to tell you when you're about to die.

I just have them in an RC helicoptor, but I'm hoping to switch my cars if I can do it safely. (big battery=big bang=missing hand

)

Post by **gannon** » Fri Sep 02, 2005 7:08 pm

hm... I just checked the pdf, and was wondering if you know that the l200 is just about the same as the lm317 regulator but can limit the output current.

segasonicfan · Post by **segasonicfan** » Fri Sep 02, 2005 7:13 pm

you can build a somewhat cheap li-ion charger from just a transistor and a resistor. Not the best but it charges.

You didn't mention the LM317. I thought you were just talking about directing voltage without an IC. Yes, the LM317 works it just has a much longer charge time. The circuit you are talking about is on the page I mentioned as well..

-Segasonicfan

Post by **gannon** » Fri Sep 02, 2005 8:13 pm

That's not the circuit I was talking about. The one I saw used a transistor to produce a better charging pattern for lithium batteries.