How can I safely charge AA batteries with solar?

I am going to build a solar charger, but I am not sure if it is safe to just apply the power from the solar panel, with a blocking diode, to the batteries to charge it.  Will this method hurt the batteries if they are charged for to long.  Could I just open up a regular battery charger and use the components in that?

Thanks in advance

frollard7 years ago
Along those lines - depends on the batteries.  Some are more tolerant to overcharging, but in general it's not a good idea to overcharge.

Methods:  Timing - knowing the capacity of the battery and the output of the cells, figure out how long it should take

Method 2 - Temperature.  When a battery gets full, it warms up (instead of absorbing the energy chemically) to release the energy being put into them.  Sense the temperature and shut off the circuit when it heats up.  Lithiums commonly use this method.

Method 3 - Voltage. Measure the voltage as they charge, and once they get to their full charge voltage, they're charged :D
NiCads are pretty tolerant to overcharging