Lipo Problems !!
 

Hi all hope you can help please, new to lipos.

im using a core-rc uac-40 charger and trying to charge a lipo 7.4v 2s losi receiver pack its coming up with ERROR LOW VOLTAGE when trying to charger and will not charge.

Ive seen on another link to charge lipo at very low rate on nimh for 30 seconds to up the rate so it can pick the voltage up, so i tried that and got it from 1.8v to 5.0v in 30 seconds but still saying ERROR when putting it back on lipo settings

Thanks Dave...:blush:

need to get above 6.4v m8

will it be ok charging it for that long as it was feathering the voltage. ie not really going up that quick. thanks

you need to get it to 6 volts this is the min that the charger will alllow them to drop to (3 volts per cell)
be vary carfull and watch them closely and do not leave them unatended, they should never be allowed to go flat

yes may take 5 ten mins just keep watching them and if they swell at all disconect imediatly

If the voltage was that low (1.8V for the 2S battery) then the chances are the cells are damaged. Typically damage occurs at <2.0V per cell. If the voltage does not recover to 6.0V then it is RIP LiPo.

N

Many thanks all...ill try it now but if bad cell why would this be as battery is only 2-3 weeks old..:thumbsup:

i have recovered many reciever packs that have been totally flat, defo worth a try

you have let it go flat....... unplug it when not in use, do you have a balancer ? if not get one asap

ye got the balancer do you balance charge it from the beginning or balance after fully charged.thanks

Ideally balance whilst charging. If the cells are out of balance and the charger stops at the required 8.4v, it maybe that one cell is below 4.2 and one is above.

Better to balance before charging if you're not going to or able to do it during charge I'd say.

You're thinkin old skool.

The balancer allows your charge current to be split between the 2 cells as is required by the cells. I don't balance charge mine every time, but more is better.
Yours being this flat I wouldn't even think of charging them without a balancer.

Your point is valid, but you can't balance before charging as the balance part only happens WHILE charging.

I'm not familiar with the Core chargers, I use a Trakpower charge through V-Balance and you can balance totally independently of charging, before or after, with that unit.

As you say, with cells as flat as they are, balancing should be done from the off.

did you leave the speedo plugged in as that'll damage it

I too use that. Are you sure you can balance without a charger?

go on then, he clearly says in post 1 is a losi reciever pack, why would it be plugged into a speedo?

he is 100% correct, to try it just plug your lipo in and the balancer will work, dont even need to use a charger. the trakpower cuts power to the cell with more charge, or it will as a stand alone drop the voltage on the high cell via a small internal discharge, for obvious reasons the pack does need more than 6 volts in it though

I guess you (I...) learn something new everyday!
Presumably it will take forever to discharge?

Taken from the V Balance manual (actually the manual for the FlightPower unit, but they work the same).