Those Motorola Power supplies that have the battery back-up feature are
really cool, unfortunately, they are also kind of rare and expensive (unless
you luck out at the swap meet or on e-bay).
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
when the relay is energized, the power is routed though the relay from the
power supply to the output binding post, the output binding post being wired
to the "throws" of the relay. When AC power is lost the relay deenergizes
and these contacts of the relay are wired to the backup battery. That takes
care of isolating the battery from the power supply, the only thing left is
a simple charging circuit. To accomplish this, an 8 Ohm, 25 Watt resistor
from the relay "throws" to the battery contacts was added. This only allows
for trickle charging, but as the battery voltage approaches the supply
voltage, the current "self regulates" to almost nothing. Also, since AC
power is present 99.9% of the time trickle charging in this way is not a
problem. This does the job nicely.
We have done this mod to 2 different repeater systems with excellent
results, and no failures of the backup system. Not as easy as buying a
power supply ready for the task, but still easy to do and I would bet,
usually less expensive.
Hope that helps
73, Wade- KR7K
----- Original Message -----
From: "Eric Lemmon" <[EMAIL PROTECTED]>
To: <[email protected]>
Sent: Monday, January 10, 2005 6:47 PM
Subject: Re: [Repeater-Builder] Micor Base Station Battery Backup Circuit
>
> Jim,
>
> The TPN1106A is one of a few Motorola MICOR power supplies that are
> designed to float-charge either NiCd or lead-acid batteries for
> emergency backup. There is an internal pot to adjust the voltage for
> the chemistry of the battery.
>
> When the TPN1106A power supply is used, the battery is connected
> directly to the same terminals that feed the PA. You cannot do this
> with other power supplies, because the battery may discharge back
> through the power supply during an outage, possibly damaging the power
> supply.
>
> The complete details of the TPN1106A power supply and the battery
> protection and alarm system are contained in a 32-page manual
> 6881104E92, which is still available from Motorola Parts.
>
> 73, Eric Lemmon WB6FLY
>
> Jim Cicirello wrote:
> >
> > "Happy New Year"
> > I am looking for a print or detailed description of how Motorola
> > hooked their Battery Backup Circuit into the Micor Base/Repeater
> > Power Supply. I found a schematic on repeater-builder 1106.jpg, but I
> > didn't get a good print out on my end. I remember seeing a portion of
> > a service manual that had the circuit, but as luck would have it my
> > manual does not have the circuit. Any help would be appreciated as
> > always.
> >
> > 73 JIM KA2AJH Wellsville, New York
> >
> >
> > Yahoo! Groups Links
> >
> >
> >
> >
>
>
>
>
>
>
> Yahoo! Groups Links
>
>
>
>
>
>
>
>
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