Sylvia Else wrote:
D Yuniskis wrote:
Sylvia Else wrote:
Michael A. Terrell wrote:
Thomas Tornblom wrote:

[attributions elided]

I have been contemplating using two full size 60Ah car batteries
externally instead of the small 7Ah internals.

Make sure you keep a couple fire extinguishers handy.

Such a modified UPS would clearly run for much longer, but given the
run time of a typical UPS on its standard batteries, I'd have thought
any heat sinks would be approaching thermal equilibrium, and wouldn't
get much hotter on an extended run.

Charging?

I think the point was that lead acid car batteries produce H2.
Quite easy to ignite *in* a house :

He could always put them outside.

Yes, this was the approach I was taking. But, for most smaller
UPS's you need 5 - 10X the desired output current from the
battery pack. So, the farther the batteries are located
from the actual UPS, the heavier the wire needs to be in order
to keep IR losses manageable.

And, the batteries are then subjected to the weather (temperature
extremes, etc)