What is the simplest circuit for limiting charging of 1.5v batteries?

[n0_3sc]

I have a cheap set of wireless headphones where the base unit supplies a voltage to the headphones to charge the 2 AAA NiMh batteries. However it has not cut-off point, ie. it'll charge indefinitely destroying my rechargeable batteries.

I'm looking for the least complicated circuit that will break the charge when the batteries are near or at max capacity.

Any ideas would help greatly.

 

[mgb_phys]

It's difficult to correctly charge NiMH batteries without either monitoring their temperature or periodically stopping, discharging at a constant rate and calculating the change in discharge rate.
The best and simple way to charge rechargables is to do so very slowly, it is difficult to damage batteries if you charge them at say 1/20 of their capacity (ie at 100mA for a 2100mAh AA)

 

[n0_3sc]

ok so if i have a high mAh batt, I don't need to worry about continuous charge damage?
At the moment its using 500mAh and the batteries end up leaking acid after time.

 

[mgb_phys]

I would get a spare pair of NiMH batteries and a cheap slow charger or one of these

(Sorry I didn't see the AAA part, the highest cap is likely to be about 800mAh - you don't have to worry about damage if you charge slow enough)