Mike wrote:

"Ian Stirling" wrote in message
...
Mike wrote:

"Ian Stirling" wrote in message
...

Any thoughts on the best products to use ?

Not really.
I haven't looked at appropriate products, due to being able to make do
with a BEST 600 UPS, fitted with 4 car batteries at a tenner each
from the scrapyard.

Searched for this on Google and only found links to the batteries used
by
it.

It's not designed to take car batteries, and is a several year old model
that was thrown out as it wasn't working (dead batteries).
I added a fan, and a slightly beefier charging circuit.

Sounds like you recommend a brew-it-yourself solution then ? :-)

In some ways yes.
However.

Many UPSs are designed for short term use.
For example, some have heatsinks that are only designed to put up with
a few minutes use at nominal load, as the tiny batteries put in it will
have discharged by then.

So you've essentially got to make sure that all the components can handle
extended loads.

Then you've got the problem of what happens if the microprocessor in the
UPS decides that the large batteries are a 'fault', and won't use them,
or the charging circuit overheats, or only charges to the original
capacity, or ....

For example, one problem with my current setup is that it takes a week to
charge after a full discharge.

And then you've got the whole issue of messing around with electronics
that can generate enough power to kill, even when unplugged.

DIY can be appropriate - but only if you know enough to safely DIY it.

There are canned solutions, but they tend to be expensive. The solar and
other groups I mentioned would probably have some ideas on the easiest
way to do it.

(If you manage to kill yourself or burn down your house as a consequence
of this posting, I reserve the right to point and laugh).