Strange- What causes this?

I have 4 X Panasonic/ Sanyo 18650GA 3500mAh batteries that are about 3 years old.At the end of the charging cyle in my Folomov A4( New Version) Two of them will be fully charged.The other Two will say NULL. I measure them and they are always around 4.0v or 4.01v.I put them in my Fenix ARE-C2 AND within 10 seconds they are at 4.19/ 20V!! What causes the Folomov to not fully charge and HOW does the Fenix charger quickly go from 4.01v to 4.20V? :person_facepalming:

Does the problem follow the individual cells, or the charger bays?

Gotta answer that first…

Good question.I have to document it the next few times.It may take a few weeks cause I dont use the light too much. TBC

My guess and bet it is the cells.I have charged hundreds of different cells in that charger.The GA’s are the only ones that do that.
They are PROTECTED.I forgot to mention that in OP.

Many 4 bay chargers don’t have the same characteristics per slot. They assume you will use the first two bays most of the time.

The protection circuit is kicking in and cutting off the charge for some reason. I’ve seen that in a few cells.
When it’s almost full and you restart it the termination current is likely a lot lower. That may avoid the protection fault.