Circuit suggestion for battery opeeration and solar panel

max72

I would like to have a suggestion for a battery operated board.
I'm thinking of using 4XAA NiMh battery pack and a linear regulator. I would like to add the 6V solar panel as an aid to increase battery life.
Please find attached the cicuit I would like to use. I would appreciate any suggestion.
My assumptions are:
- Components should be hand solderable, SMD is ok.
- A switching regulators offers limited advantage for this type of battery input over linear regulators (for instance lm2594-3.3 requires 4.7 volts minimum, and many buck-boost use a linear stage when in buck mode. Hand solderable buck-boost are difficult to find)
- While open circuit voltage of a solar panel is above 7V the voltage instantly drops with current flowing
- even if with fully charged batteries, and in better than optimal conditions, a less than 200mA current flow from the panle is almost a trickle charge cuurent. Moreover it is a remote opportunity
- no voltage limiting (zener) is needed
- a schottky diode would avoid current reversal in the solar panel, at the cost of a limited voltage drop

Thanks in advance,
Massimo

kwinn

The only problem I can forsee is the possibility of overcharging the batteries and shortening their life, and even that is unlikely. Only way to find out is to try it and see how well the batteries fare.