I have had good luck using a pair of diodes to isolate a power supply from a charging circuit. I essentially have a Statpower 10amp battery charger (specifically designed for the flooded cells I am using). The batteries float on the charger voltage when the AC power is available. The battery positive lead then feeds through a diode and joins the "positive power bus" of my repeaters. Using a proper charger is the most important part so you dont boil off the electrolyte in your batteries.
The positive power bus is fed from a large GE power supply. The positive lead from the power supply feeds through a diode to feed the power bus. The idea of using a diodes is to keep the higher voltage of the power supply from passing current into the batteries when AC is available, and vice versa when AC is off. However, if you are using a high power PA or your repeater draws more than about 20 AMPs on TX, you have to be careful of your choices of diode. I use large feedthrough diodes, mounted on large heatsinks, but on lower current draw you could get away with using a smaller bridge rectifier mounted to an unpainted metal piece in your repeater cabinet with some heatsink compound. Dave Cameron VE7LTD --- In [email protected], "wm5c" <[EMAIL PROTECTED]> wrote: > > Hi, > > New member here. Thanks for allowing me to join. > Our club has acquired some large lead-acid 12v batteries we would like > to use to back up our repeater in emergency situations. Does anyone > know of a good (but simple and inexpensive [we are a very small group > in a very small town]) circuit to accomplish this? Any input would be > appreciated. > > Danny WM5C > Heart Of Texas Ham Operators Group (HOTHOG) > Brady, TX > www.hothog.org >
