I prefer solid state isolators between the batteries & the supply.
West Mt.'s was reviewed in a recent QST (see below), and Duracom (&
others) have similar units at varying prices. I recommend them
highly, and use them in commercial, public utility, and public
safety applications.
I have problems with relays, especially inexpensive ones. They will
fail sooner than the iso-diodes. Granted, it maybe a year or 3, but
if constantly energized, I've seem some cheap relays become
magnetized and not release, I've seen coils go open, thus running
the batteries instead of the A/C mains, and I've seen more than one
catch fire (A mini-blaze confined to the enclosure), and if hooked
in on the A/C side of the supply, the system isn't protected from
power supply failure.
...I don't mean to be judgemental; these are just my brain
dripppings.
___________________________________________________________________
> A friend of mine and I designed a very simple circuit to modify the
> Astron 20A Power supplies to do this job. Obviously this could be
> done on any power supply but the Astron 20A is common and
> inexpensive and they leave enough room to put this all inside
> easily. The first thing you will need is an A.C. operated relay.
> Radio shack has one that we chose simply because they are cheap,
> $8.00 and the contacts are rated high enough to handle the
> 20 Amps. It is RS P/N 275-0217. The contacts are rated for 10
> Amps but since this is a double throw type, both "throws" can be
> tied together. I drilled another hole in the rear of the Astron
> to mount another binding post for the battery connection. The
> relay coil is connected directly to AC power coming in, the
> contacts are wired to the 13.8 VDC output wire so that
<<--clipped to conserve bandwidth -->>
>
> > FWIW, the Feb. QST (pg 78) reviews a "PWRgate PG40" by West
> > Mountain Radio. Basically it contains two 80 amp Schottky diodes
> > on a heat sink and three Anderson Powerpole connectors. The
> > diodes drop about 0.4 volts under load. It's designed for forty
> > amps. It sends whichever input voltage is higher to the output
> > and will isolate your power supply from the battery. That is,
> > if the AC fails to the power suppy, the battery won't back up
> > into the power supply. It apparently also has a diode and
> > resistor that can be used to charge the battery from the power
> > supply at a rate of up to one amp. (Would take days to charge
> > your marine batteries!) I think it may be a bit over priced at
> > $69.95 but it or something like it may be an answer to your
> > situation.
> >
> > 73,
> > Al K9SI
> >
> >
> >
> > Date: Fri, 21 Jan 2005 17:11:37 -0000
> > From: "w9mwq" <[EMAIL PROTECTED]>
> > Subject: Powering the Repeater With Marine Batteries
> >
> >
> > Last night my power supply took a dump! Good thing for backups.
<<--clipped to conserve bandwidth -->>
>
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