uneven discharge

[calebra]

3 batts in series in an RRT 3, after a days work i have noticed that one of the batts has 1.7 to be charged and the other 2 have .7 to be charged. this has me baffled, is this safe? am using AW 2600's.

 

[mdocod]

1.7 what? 0.7 what?

We need higher resolution or at bare minimum, a few descriptors here....

I'm going to assume volts...


Keep in mind that it's normal for the lowest capacity cell in a bunch (may only be a few percent lower than the others) will hit the low voltage cutoff and measure around 2.5-3.0V and be dead, while the others may be reading 3.5V.

The difference in state of charge between 2.5V and 3.5V is like 5-10% on a li-ion cell. The difference between 3.5V and 3.7V is like another 10%, it is not a linear thing, the useful range is ~3.5-4.2V on most li-ion cells.

Also, it's not unusual for the cell closest to the LED that is heated the most during the discharge to wind up expelling itself the fastest.

Eric

 

[calebra]

ok, i will try to make myself clearer, 1700ma and 700ma. the one batt discharged 1000ma more than the other two, so my question is, is this above the norms or acceptable, is it a faulty batt maybe?

 

[Popsiclestix]

Perhaps you mean mAH?

What kind of device are you using and what procedure are you using to determine these values?

 

[SilverFox]

Hello Calebra,

It looks like you use your light for awhile, then noticed that two of the batteries required 700 mAh of charge to fully charge, and one of the batteries required 1700 mAh of charge to fully charge.

This seems to be an imbalance situation. There are at least three basic causes of this. First there could have been a charger malfunction and when you put the batteries in the light, one of them wasn't fully charged. The second is that one of the batteries is not in good health. The third is that there could be an increase in internal resistance in one of the batteries or a protection circuit that is on the verge of malfunctioning.

To sort this out you will have to do some testing.

Charge the batteries and leave them sit off of the charger for an hour. Then measure the resting open circuit voltage. They should all have the same resting voltage.

Next, put the batteries in the light and run it for about half of its run time. Let everything rest as the batteries cool down, then measure the resting open circuit voltage again. In this situation, the voltages should be close, but may not be exactly the same.

Finally, charge the batteries up again and see how much you put back in.

If the same battery is acting up again, purchase some new batteries for the light, use the under performing battery in a single battery light, and keep the other two batteries for a two battery light, or for back up for your single battery light.

Tom

 

[calebra]

Hi Tom, thanks for ur help here, one thing i have noticed whilst charging the unevenly depleted cell that the charger took 2 hours to charge 1600mah at a rate of 2600mah, so i am assuming i received a dud batch from AW as these are new cells and have used them a few times under normal conditions.

 

[calebra]

Perhaps you mean mAH?

What kind of device are you using and what procedure are you using to determine these values?

BC 6 hobby charger

 

[calebra]

have done a few more tests with AW's batts, couldnt find 2 that behaved the same, not even close. ran the same tests with wolfeyes batts, couldnt find 2 that differed. lesson learnt i guess. no need to ask the question, as i have close to a 100 AW's, and i dont feel impressed right now.