Anyone know a link to a micro usb input board to charge 3 cell lipo

[charleshodge]

Found a bunch that will charge one cell lipos but not 3 cell.want a chip orboard,preferably small that takes a phone charger and charges a 3 cell lipo.any help will be appreciated.

[clouseau]

Wrong one!

[clouseau]

This is the only one I've ever seen ands its not really a true balance charger cause you have to charge 1 cell at a time.

http://electronics-diy.com/electroni...tic.php?id=808

[setishock]

If you use a USB wall wart to try and charge a 3 cell LiPo, you're going to pull far more current than the charger can handle. Besides USB chargers only output 5 volts. A 3 cell LiPo is 11.1 volts.
Even with a stepup regulator, there's just not enough current available to charge the battery.

[yakky]

Originally Posted by setishock

If you use a USB wall wart to try and charge a 3 cell LiPo, you're going to pull far more current than the charger can handle. Besides USB chargers only output 5 volts. A 3 cell LiPo is 11.1 volts.
Even with a stepup regulator, there's just not enough current available to charge the battery.

Maybe not enough current if you are hoping for a 10 amp charger, but plenty of USB 2 amp chargers exist. Its not going to charge a 3 cell fast, but it will get it charged. Charging in parallel, you'd get a little under 0.7 amps. No biggie.

[setishock]

But to charge a battery you have to have more voltage going in than the battery is rated at. Ok so let's say you get a step up regulator that has an adjustable output. You have to set the output to at least 13.8 volts with no load. Then you connect the battery and have to readjust the output to 13.8 volts. The current is going to drop a bit as the regulator needs some of that to operate. So let's say you have 1.5 amps on the output with the battery connected at 13.8 volts.
That power supply is going to get hot and getting hot reduces it's efficiency.

My question is why bother with all that when you can get a charger for a song and a dance that will run off 110 from the wall or a cigarette adaptor that plugs in to the lighter socket or an aux socket you can install yourself? If he's planning to charge batteries off his lappy, he better be careful. It's all to easy to blow out the usb power regulator. Besides any charger worth its salt is adjustable and has an lcd screen so you can see what's going on. LiPo's are inherently dangerous and mostly in the charging stage.

[yakky]

All modern lipos are several batteries in one. With 5 volts you can charge each cell to 4.2volts via the balance leads, no problem, no voltage step up needed.