Re: [A/S] Blocking diode (?)

[Jerry Flanders <jeflanders@xxxxxxxxxxx>]

Yes - and you have named it exactly right - it "blocks" the reverse 
discharge through the solar panel. Solar panels will definitely allow your 
battery to discharge through them unless you have that blocking diode in 
the circuit. Some apparently have it wired in permanently as a part of the 
panel, some do not.

Sounds like your panel is a low-current panel, so the smallest power diode 
(say, one amp or larger) you can buy at Radio Shack will work if you can 
wire it in. You need to put it in the wire from the panel to the + side of 
the battery. If you get it right, the battery charges properly. If you get 
it wrong, the battery does not  charge, and instead discharges through the 
solar panel - no big technical tests to worry about. If I am remembering 
the diode coding correctly, the "banded" end of the diode will go to the 
battery side. When you look at the diode, "banded" will make sense.

There is a minor technical difference between diodes - a Germanium diode 
would be preferred, but you will probably only have the Silicon ones 
available. Don't worry about the difference - just use whatever power diode 
of 1-3 amps he has. Don't worry about the voltage rating either - his least 
rated is probably several hundred volts, and you only need 20 or so - no 
harm in the "over-rating" on voltage (PIV).

If you want a specific rating, just get the common 3 amp 400 PIV silicon 
power diode - Radio Shack store. Probably 2-3 for a dollar.

Good luck.

Jerry W4UK