Charging NiMH at lower/higher voltage

Hi,

I'm trying to make a solar charger for some of the cells I use in my flashlights.

I read that if you are going to use a trickle charger that the charging voltage for NiMH should be from ~1.4V-1.6V.

What happens if I charge them at ~1.2V? Does the cell just not get completely charged?

In the same respect, if I have a solar panel feeding 1.7V into a cell, would it be damaged? Or is the current flow too low to damage the battery?

Thanks.

The charging voltage has to be higher than the voltage in the cell. Otherwise the electrons will flow out of the cell. If you charge at 1.2V, the cell will reach 1.2V and stay there indefinitely. Feeding 1.7V into a cell during charging is one thing if you have a smart charger that measures the cell's voltage and cuts off current when the cell is full, and is quite another, much more ruinous, thing to do to a cell without a bunch of circuitry to terminate the charge. If you are charging very slowly, you should be able to get away with using a resistor to drop your solar cell's output voltage down to ~1.40V and connect your NiMHs to that.

Have you seen FS: Solar Powered li-ion Chargers? USB out so can use a variety of USB chargers.
Norm