I was thinking the UPS might need more than 25 Amps depending on the
load connected.
>
> > so I thought of using a spdt relay with
> >the coil connected to the AC that would connect the battery when
> >the ac drops out. The advantage I see here is the circuit that
> >connects the batteries uses no power and has no voltage drop
> >while you are on batteries.
>
> There are problems connecting batteries in parallel. See my
> previous posting.
The batteries would not be in parallel - the internal battery
could be connected to a relay that would drop when the external
battery kicked in. Maybe triggering the relay with the low battery
signal and making sure it latches until the AC is restored. Of
course latching relays are more expensive and harder to find. You
would want a small amount of time where both batteries we connected in
parallel to keep the UPS output from dropping during the transfer.
If the UPS cleared the low batt indicator, and the PC was monitoring it,
the system should be able to run until the external battery is spent -
retriggering the low batt signal and causing a hopefully orderly
system shutdown.
> >
> >I have been working on a similar system to keep my rig powered when
> >I loose AC. I use the relay to connect the battery to the charger
> >while the AC is on (actually while my 12v power supply is on since the
> >relays I am using have 12v DC coils), and to the rig when the AC drops.
> >The radio doesn't seem to mind the momentary power glitch when the
> >relay drops.
>
> The computer might not like it, if directly connected, but the
> UPS should take out the glitch, if I understand correctly that
> you are using the UPS and just using the other battery to extend its life.
Actually I am not using a UPS right now - I have the setup on
my 12V DC radios only.
>
> -------------------
> Be nice. It doesn't take any longer.
> -------------------
> Charles Greene
> Internet=iqepny.rxjgwdct@rele.tunk.net
> Internet to Amprnet=ugyplz.pspf@mx.dy.fi
> 115 Aaron Avenue
> Bristol, RI (On the shore of beautiful Narragansett Bay)
>
-Pat