Request for flash-charger circuit (fully charge,flash become shorter)

[tengyy]

I need to design a solar energy source charger. It is around 5V input to charge 4 sets 1.3V AA Ni-mh 1100 mAh

Flash-charger, which has a single LED on when charging and when it reaches full, it will pause until the terminal voltage of the cell has dropped a little and then charge to the limit again etc. - the flashes will become shorter, as the cell is topped up after the initial charge.

 

[Audioguru]

AA size Ni-MH cells are 2300mAh today and have been for at least 5 years, not just 1100mAh and hold their charge for one year (old ones held a charge for a month or two).
They are charged with a limited current and there is no voltage limiting, when the cell is fully charged and is still charging then its voltage drops a little which the modern charger IC detects and shuts off the charging to prevent over charging.
Each cell will be about 1.45V when fully charged so 5V is too low (4 x 1.45V= 5.8V) to feed the charger.