Power Supply for Floating Pb Batteries
One power supply I have used for my packet system, which is a floated on gel-type battery, was to use a 12V regulator IC 7812 and offset adjustment to get the O/P up to 13.5V which is the maximum for gel types in float use.
Because it is for a float battery and I don't want any back discharge on the mains, I put a 1A diode in series with the battery.
A variable R in the common leg of the regulator (multiturn say 10K?) will vary the output voltage as the regulator puts a constant current (typically 50uA) out on the common leg.
The regulator input needs to be at least 18V DC for the max 1A O/P and the regulator will need a heatsink (insulation kit?), so the transformer (18V AC), bridge and cap need to be able to supply this. The 0.1uF cap across the regulator O/P are for stability.
For 6V battery, use a 5V regulator IC 7805, and adjust for 6.95V. For much less current than 1 Amp use 78L12 or 78L05 for 100mA Max. All regulators of this type are current limited just over their maximum current, they also have thermal shutdown.
73 De John, G8MNY @ GB7CIP
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