Charging LiPo Batteries

Community General Discussions
1

Hi;

I have a Turnigy 2 Cell 7.4v 2200mAh battery and iMax B6AC Balance Charger.

I have read a warning not to over discharge or over charge these batteries so whilst I have been using the battery in my robot (2 low power DC motors which operate at 3 - 6v 150 - 200mA, an Arduino Nano and a 9g Micro Servo. I have been monitoring the voltage, I checked it today and its 7.38v.

I thought I'd check whether it now needs to be charged and having never done this before thought I seek some advice.

I found this article which is pretty in depth but states that a battery will be fully charged when each cell reaches 4.2v (from its nominal 3.7v).

I can't find a data sheet for the battery but have just read the charger instruction manual which gives a couple of warnings one being that a batter that is fully charged or only partially discharged should not be charged.

Question: When and how do I know when this battery needs to be charged?

 


2

4.2v is the max per cell,

4.2v is the max per cell, 3.3v is the minimum
https://en.wikipedia.org/wiki/Lithium_polymer_battery

Since you are using an arduino i wouldn’t let the battery go under 7v as the 5v regulator may lack enough power to supply a stable voltage.

Usually one cell discarge more than other, but if you use a balance charger, it will restore balance.

3

Thanks Silux, I had just

Thanks Silux, I had just been reading up on LiPo batteries, I have placed it on charge set at 2.2A for a 2 Cell 7.4v LiPo Battery.I’ll leave it on charge until it reads 8.4v.

It’s a balance charger so I have followed a guide to get it all connected but the damm charger uses Deans connectors and the Turnigy LiPo’s are XT60’s. Luckily I had bought a pack of Male and Female XT60’s when I made up a power connector for the Bot. Just lobbed off the Deans connector and soldered on an XT60 complete with heat shrink.

7.82v and counting.

All articles suggest an 80% discharge rule, i.e. make sure your batteries don’t go below 80%, so that’s about 7.44v min for a 2 Cell LiPo (very confusing when the battery is rated at 7.4v??  I was a tad under that at 7.38 but hey ho, i’ll keep an eye on it next time, maybe I’ll fit a battery warning system, should be pretty simple? 

4

I believe it’s 80% of the
I believe it’s 80% of the nominal 7.4 voltage of the battery or 3.7v per cell.

You shouldn’t have to monitor a good LiPo battery charger and you shouldn’t be using anything else to charge it. Each battery chemistry has different charging patterns. In other words, if the charger does LiPo and you have it setup correctly, then just let the cycle complete and all will be good.

5

I kept an eye on the charger

I kept an eye on the charger and the voltage hit 8.4v so I interjected and stop the charge. Its a SkyRC B6AC iMax balance charger, should I have left it and would it have stopped itself?

 

 

6

usually chargers have "do

usually chargers have “do not let unattended” on the manual.

7

I think the charger has an
I think the charger has an auto stop function, it’s called an “intelligent” charger by the way

8

the lower cut off has a bit
the lower cut off has a bit of ambiguity. The emax ESC I use,with SimonK firmware, is pre programmed to stop at 3V per cell, though I have managed to raise an alarm at 3.3V.

9

the lower cut off has a bit
Double Click mess