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.