Tom Walker wrote in a message to Maurice Kinal:

->  RT> A UPS is definitely on my list of stuff to get.  Even if I can find
->  RT> one which needs batteries,  since I have batteries...

-> Me too but my plan is to just use the batteries as a power source. 
-> The plan is to get all the computer stuff off the grid.  Having two 
-> gel batteries would allow a backup while the other gets charged up.  
-> They are extremely good batteries and if I keep everything to a 
-> minimum I think they should run for days, maybe even weeks, per 
-> charge.  That is the plan.

 TW> WEEKS, I hardly Think so. Rembember the rating on those UPS units
 TW> is typicaly for 15 Minutes. You would have to Multipuly the Battery
 TW> size by a factor of One thousand Three hundred Forty Four to get
 TW> Two Weeks. That is a good sized battery bank. They are availble but
 TW> Do you have the Room and can you Afford them.

The last UPS I looked at in a store was actually marked honestly,  with a
run time _at full load_ of a whopping 3 MINUTES!  I saw that and
immediately lost interest.    The last one I had working would
support a computer system and monitor for maybe 20 minutes,  altogether.

That aside,  Maurice isn't talking about the inefficient setup of a typical
UPS followed by a standard power supply (also less than 100% efficient). 
He's talking about stuff that's designed from the start to deal with a
12vdc input.  Also stuff that's designed for lower-power consumption to
start with, as compared to standard clone hardware... 

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