Willis, I have used a simple diode circuit in several
repeaters I have converted to battery backup. I like
the solid state solution more than a mechanical relay
for reliability.
The circuit is as follows:
Place a diode in series with the output of your power
supply. (it can be the internal supply)
Place a diode in series with the battery output to
your repeater load.
Place a diode and resistor (10 ohm 25 watt) in series
between the power supply output and the battery.
All diodes have their cathode or bar pointed toward
the load. Choose the diodes to carry the current the
repeater is drawing. (the battery charging diode
needs to only handle a couple of amps) If the battery
goes down completely, the resistor limits the charging
current so the power supply is protected. Raising the
output of the power supply by .7 volts to overcome the
drop in the diodes would bring the power back up to
what it was. Another factor would be to adjust the
power supply output so that the battery floats at 13.5
VDC for optimizing the battery charge vs electrolite
loss.
73 - Jim W5ZIT
--- "Willis M. Hagler" <[EMAIL PROTECTED]> wrote:
> Hello Everyone,
>
> I am wondering what repeater operators commonly use
> when a 12v power
> supply as well as a battery charging and switching
> system is needed at
> a repeater site.
>
> My repeater has an internal 120v power transformer
> that feeds a 12v
> regulator box, and also has a battery circuit on the
> back of the
> repeater that will allow it to draw from batteries
> when the main power
> is lost. It supplies a very low current trickle to
> keep the batteries
> charged up, however if the batteries drain due to
> extended power
> outage it does not provide any sort of reasonable
> facility to charge
> them back up again.
>
> The manufacturer recommends to take the batteries
> off, charge them
> externally, and then return them to float charge...
> however that's not
> very feasible if the repeater is located on a
> mountain or some other
> location that's not easily accessible on short
> notice.
>
> I'm thinking of just ditching the internal power
> supply and building a
> more robust off-board power supply and battery
> charging system that
> can switch onto the batteries and charge them up
> again when the main
> power returns.
>
> For use at home I like the PWRGate units which
> maintain the batteries
> nicely but I am wondering if others have used those
> at repeater sites
> with no trouble?
>
> Thanks anybody who has information to provide. This
> group is a
> wonderful resource for all things repeater-related.
>
> Yours,
>
> Mark Hagler
> W7WMH Seattle
>
>
>
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