Problem with the Folomov A2 charger

[passi69z]

Hello,

recently I bought a Folomov A2 charger to charge a few Li-ions and NiMH cells.
Charging Li-ions works great - but yesterday I tried to charge a few older and newer NiMH cells I bought from a discounter (Aldi). The cells are AA ones with a rated capacity of 2400mAh and a recommended charging current of 460mA. At first I tried 4 months old ones that have never been charged. I put them in at the same time, choose a current of 500mA and the charger showed me the following capacities in %:

Slot 1: 1%
Slot 2: 2%

After letting them charge for a while the charger showed me this:

Slot 1: 34%
Slot 2: 60%

After another while:

Slot 1: 80%
Slot 2: 77%

And then it stopped (I think it stopped) charging at:

Slot 1: 86%
Slot 2: 84%

the + side of the cells looked like the cells were leaking (some white dirt was on there) and the cells did not work in my flashlight.

And now to the other NiMH’s I’ve got (3 years old - once used):

Pretty much the same as the ones mentioned above. But they didn’t leak and worked in my flashlight.

I have no idea what went wrong, do you? :question:

[SIGShooter]

What brand of batteries are you trying to charge? If they were at 1% it doesn’t sound like they were lsd batteries.

[passi69z]

As mentioned above they were from a discounter (ALDI), no-name cells. They were like 3€ / 4 pieces.

[BlueSwordM]

@passi69z, that behavior is perfectly normal.

Chargers can only use voltage levels to signify charge levels.

And since NiMH battery voltage varies even less than lithium-ion, a 1,2-1,3V stored NiMH battery will be seen as discharged, even though most of the capacity is still usable.

Also, try to charge at 1A instead of 500mA. 2400mAh cells have no problem handling 1A, and chargers have difficulties determining when to end charge at low currents, so 1A is about perfect for charging NiMH AAs, and 500mA for AAAs.

[passi69z]

@BlueSwordM

@passi69z, that behavior is perfectly normal.

Chargers can only use voltage levels to signify charge levels.

And since NiMH battery voltage varies even less than lithium-ion, a 1,2-1,3V stored NiMH battery will be seen as discharged, even though most of the capacity is still usable.

Also, try to charge at 1A instead of 500mA. 2400mAh cells have no problem handling 1A, and chargers have difficulties determining when to end charge at low currents, so 1A is about perfect for charging NiMH AAs, and 500mA for AAAs.

So it’s normal that the charger displays 86% ans the cell is full?

And do you think the ones that leaked were overcharged due to the low charging current?

[SIGShooter]

@passi69z

@BlueSwordM

@passi69z, that behavior is perfectly normal.

Chargers can only use voltage levels to signify charge levels.

And since NiMH battery voltage varies even less than lithium-ion, a 1,2-1,3V stored NiMH battery will be seen as discharged, even though most of the capacity is still usable.

Also, try to charge at 1A instead of 500mA. 2400mAh cells have no problem handling 1A, and chargers have difficulties determining when to end charge at low currents, so 1A is about perfect for charging NiMH AAs, and 500mA for AAAs.

So it’s normal that the charger displays 86% ans the cell is full?

And do you think the ones that leaked were overcharged due to the low charging current?

I don’t know of any charger that reports 86% full when the battery it is charging is fully charged. If you have a DMM you can see what the battery voltage is when it’s fully charged. It should be around 1.45v or higher when it comes directly off the charger. Not all chargers use voltage to determine if a NiMh is fully charged. Many do but others use other algorithms instead.

According to HKJ’s review of the A2 it terminates on voltage so to me it seems that either the batteries are bad or the charger is bad.

[passi69z]

Just got some new eneloop pro cells. I will discharge them now and charge them afterwards to see if the charger or the cells caused this problem.