As yesterday, my GP Recyko+ AA batteries of my camera, reached EOL when i wanted to photograph a rare meeting with a GE M250R2 road lantern with a 250W SBMV (The camera turned on and back off and displayed "Replace the batteries" and refused to operate even when i tryed to reinsert the batteries, despite they were charged several days ago and wasn't used so much), and based of things that Medved and other members of LG said me about fast chargers, i bought a slow charger GP Powerbank S390, and charging the spare GP Recyko batteries that i have.
Despite the charging time of the charger is 12-15 hours for the capacity of my GP Recyko+ batteries (2050mAh, so the charger supply ~200mA for the batteries during charging), they gets warm during charging, similar to my GP Recyko+ 2 hours Fast Charger, although less than the last charger.
Why my batteries gets warm even with the slow charger?

I think that i found the reason for the heating up of my GP Recyko+ batteries in my GP Powerbank S390.
One of the tutelaries in the hostel i live in, have also this charger, and he got me an information that led me to the conclusion that i have been entrapped when i bought this charger.
This charger have no Full Battery indicator (The red LED charging indicators are lit forever), and it continues to charge the batteries even when they are full (Like the chargers of UPSes, emergency lighting systems and wireless phones).
The charging of the batteries when they are full, is what causes them to heat up.

If you get "crystal packs" built up, the batteries will get warm in a slow charger. In a fast charger they will get hot. A couple DEEP cycle discharges will most of the time take care of that.

The problem is not the slow charger without termination (the C/10 current does not need one, provided you do not leave the cells there for weeks), but the high current digital cameras ask for. It make the setup very sensitive to the cell internal resistance increase over life - normal NiMh wear out mechanism, but accelerated by the high current operation (with slow charge rate the cells are not stressed by the charger).
Therefore the NiMh lifetime in digital cameras is few 10's of cycles, I've never seen it reaching 100.
Worst are cameras using only two cells (the "2xAA/CR-V2"), the only 2.4V yield to really huge currents. With these is better to use the Lithium CR-V2 and switch to new, freshly bought NiMH's only for events, when you expect heavier camera usage (so the primary CR-V2 would become too expensive) and throw them out (or redirect for use elsewhere) afterwards (so you won't get annoyed with them by the nonworking camera; usually they barely survive the 3 week vacation with one cycle for each day).

What would be bad with multiple cell batteries, is not fully charging all of the cells. The overcharging (it should be at low rate) is the only method equalizing individual cell charge levels, so the few hours extra (after full charge) is actually essential to avoid cell voltage inversion problems (mainly in cameras using 4 cells).

The main benefit with low selfdischarge cell types for digital cameras is (in most cases; why I recommend these cells for cameras) the camera use pattern: The camera is sitting in the drawer, occasionally taken out to make few pictures and then put it back - standard NiMh's are usually empty after week of sitting in the drawer...
But with heavy use they won't last longer than the standard types, they degrade by the same means, it is normal.

To date changing from ordinary NiMH to Recyko's in the parents camera (2xAA) did huge difference. The Recyko's really work amazing well

I think you have to try to recharge the batteries few times more

Typicaly heating batteries = end of charging. That or someting went wrong in the battery but you still can try to discharge and charge again

Another point : There may be a spot of oxide etc (bad conductor) on the battery terminals or in the camera, forming resistance in series with the battery and making the camera _think_ that the battery is bad (as the voltage the camera sees is that of a bad battery)