I have a large amount of UPS experience, from simple 300VA PC UPSs, to whole
room 25KVA units, to whole building UPSs with generator backup. One can not
get away with using one of the small self contained UPSs with a 100 watt
radio without having AC power or a genny running main power at all times. It
is good for smoothing out the ups and downs and brown outs from a genny. If
the genny goes down or you lose AC mains, the little 7 amp battery inside
the UPS can not handle the load of the DC power supply and radio. It is just
simple math, one does not have enough current from the 7 amp 12 volt
battery. The UPS is taking the 12 volts at 7 amps and making AC from it,
powering a DC power supply, to power a 100 watt radio. We are way short of
the current needed from a 12 volt battery to get over the power outage.
One way to help this is to get a 600VA or higher PC UPS, unplug it from any
power source, and remove the internal battery (or batteries). Now follow the
battery wires back into the unit and find a good place to tap in and upgrade
the wire size and add a fuse. Use enough wire to get safely outside the UPS.
Now add the proper number of 12VDC automotive batteries in series or series
parallel (depends on whether you need 12 or 24 volts). Now you have a UPS
that will run your the DC power supply though a generator fuel refilling as
well as provide smoother brown out free power to the DC power supply.
During the last VHF/UHF contest, Cliff (KD4GT) and I ran a Best 1.2KVA UPS
with two 12 VDC batteries off a genny to power a 800 Watt 120VAC 6 Meter
Amp, DC power supply, and Ten-Tec 526 6N2 radio. It worked great and we even
operated full power during generator refueling. The real bonus was that the
UPS kept the Amp at full tilt during the lag time of the genny ramping up at
Amp key down. In fact, the Amp preformed better on the UPS/Genny combo then
it does at my home where I have an upgraded electrical service.
UPSs are very useful for Field Day and other remote power requirements where
a generator is going to be used. Afraid to plug a desk top PC into a genny
for logging, put a UPS between the genny and the PC. Field Day rules have no
problem with one doing this with a PC or that nice AC powered 200W Home Rig.
The power source is still the generator. With the smaller VA UPSs upgraded
to use external 12VDC automotive batteries, be sure to start with already
fully charged batteries. The small trickle chargers in the PC UPSs can not
bring weak batteries up to full charge over a contest weekend when asked to
run during outages and smooth out power.
Hope this was helpful. 73 Keith
de KE4TEG
----- Original Message -----
From: <AC5E@aol.com>
To: <tentec@contesting.com>
Sent: Wednesday, May 21, 2003 3:23 PM
Subject: [TenTec] RE: Experience with UPS and ham rigs
> Since it's been suggested - I have tried several "small" 375-425 VA UPS
on
> an Omni VI - usually to allow us to operate FD while the generators were
> shut down. The setups were Astron 35's powering the rig and a keyer, and
the
> usual result was a blown UPS fuse within a few seconds of changeover - and
in
> one case a well fried UPS.
>
> I think the problem is with the really poor output of the cheaper UPS,
since
> a couple of "pure sine wave" 1500 VA UPS did quite well. But those big
boy's
> are a long way from cheap.
>
> And, one more thing. You definitely want to proved forced air ventilation
for
> any unsealed lead acid battery you might be using. A little accumulated
> hydrogen makes a big bang.
>
> 73 Pete Allen AC5E
>
>
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