There are a couple of ADC's (Analog to Digital Convertors) in that circuit
which will be used to measure the voltage, however the "guts" of the
system will be in the controlling software of the microcontrollers, so
it's very hard to see what is going on. However if this really is the
circuit of your UPS then it is a fairly advanced unit compared to some
that I have seen.

That being the case I would seriously consider replacing the batts with
the correct or near correct type rather than hacking something into them.



Andy



On Sat, 11 Jul 2009 12:12:17 -0000
"brekaman" <g4yrz@...> wrote:

> --- In GEO-Subscribers@yahoogroups.com, Andy Eskelson <andyyahoo@...> wrote:
> >
> > The problem will be the charger, how much so will depend on the method
> > that the USP uses to monitor the battery.
> >
> > Firstly the charger would have to run almost ten timer longer to charge
> > the batts, This may be a problem as the charger could work on a time
> > basis, or a voltage measuring system.
> >
> > The higher capicity batts would also have a lower resistance, which might
> > cause the charger to overload/fail. a bit unlikely but without knowing
> > exactly what the charge circuit is doing it's a risk.
> >
> > Next problem is that once charged the batts have to be kept that way. A
> > timed top-up at a fixed current would not be suitable. If the top up is
> > done via voltage monitoring then that might work, but the charger might
> > not like it.
> >
> > If you keep the big batts charged via another means, then you have to
> > somehow disable the UPS charger while the other charger is working just
> > in case.
> >
> > It really is a bit hit or miss without detailed knowledge of the circuit
> > of the UPS and how it is working.
> >
> > If the sealed lead acid 17Ah are expensive, maybe a couple of
> > motorcycle batteries would be a cheaper option.
> >
> >
> > Andy
>
> Hi Andy,
> Thanks for the reply, There are circuit diagrams here:
> http://www.fieldlines.com/story/2004/4/21/51021/8601
> but I'm afraid I don't understand circuit diagrams so good as block
diagrams.Not sure if these are for my exact model but it says smart ups. If you
want to email me direct that's fine.
> Best Wishes
> Rob.
>