What sort of diode do you need when putting a solar cell on a battery powered device?
There are two basic types of diodes; Silicon and Germanium. I
would use germanium because it has a lower forward bias than
silicon. I suspect that what you really want to know is how to hook
up an isolation diode. This is a diode that is installed in series
with the alternate power source to isolate one from the other.
Whether you use germanium or silicon the way that you want to hook
it up is pretty straight-forward. go ahead and hook the negative
(black) lead of the solar cell to the negative (black) lead of the
battery. Hook up the positive (red) lead of the solar cell to the
anode of the isolation diode and the cathode end of the diode hooks
up to the positive (red) lead of the battery. You can identify the
anode and cathode ends of the diode by looking on the diode - you
will see a little diagram that looks like an arrow with a straight
line at the tip of the arrow. the straight line side is the cathode
end. Unless you have a really big solar panel you could probably
use a general purpose diode such as a 1N4001 silicon (available at
radio-shack)Hope this helped you.