Lipo Problems !!

[pistol_pete_2011]

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...

[jayst]

need to get above 6.4v m8

[pistol_pete_2011]

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

[mark christopher]

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

[mark christopher]

Originally Posted by pistol_pete_2011

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

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

[neiloliver]

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

[pistol_pete_2011]

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

[mark christopher]

Originally Posted by neiloliver

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

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

[mark christopher]

Originally Posted by pistol_pete_2011

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

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

[pistol_pete_2011]

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

[VintageRacer]

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.

[Col]

Originally Posted by pistol_pete_2011

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

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.

[Col]

Originally Posted by VintageRacer

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

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

[VintageRacer]

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.

[bigred5765]

Originally Posted by pistol_pete_2011

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

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

[Col]

Originally Posted by VintageRacer

V-Balance and you can balance totally independently of charging, before or after, with that unit.

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

[mark christopher]

Originally Posted by bigred5765

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

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

[mark christopher]

Originally Posted by Col

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

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

[Col]

Originally Posted by mark christopher

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?

[VintageRacer]

Originally Posted by Col

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

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

The V-Balance unit can also be used as a stand alone cell balancer without connecting it to a charger, simply connect the pack to the V-Balancer by the balancer connector and the V-Balance will equalise the charge of your battery pack (as long as the pack is not over discharged). The V-Balance has a low voltage cut off of 3.0V per cell to prevent deep discharge. Your V-Balance unit also features a battery fuel gauge for checking the state of charge of the total pack and of individual cells.
To access this feature simply connect your FlightPower pack to the V-Balance unit as described before, the V-Balance will automatically turn on and go into smart balancing mode. On the right hand side of the unit is
a four bar battery fuel gauge; this will illuminate to indicate the state of charge of the connected battery.