On Wednesday 16 November 2005 18:08, Ted Harding wrote:
But I just don't know what these sorts of basic lead/acid battery can stand. Any knowledgeable folk out there?
A quick look at the battery in a 500VA APC UPS - 12v 7AH. At full load, this gives me a 2 minutes, or 14 minutes at half load. A typical car (or motorcycle) battery would extend these times considerably.. Car batteries can deliver in excess of 350A for very short periods.
I'm not into using the UPS for long-term backup. The real need is
a) To kick in and stabilise the output voltage when the mains voltage droops (fairly frequent)
b) To supply power during brief outages (a few seconds, and pretty frequent, often accompanied by spikes)
c) To supply power for at least 5 minutes when the mains goes down altogether, allowing the machines time to shutdown cleanly under cntrol from the UPS (happens often enough not to be ignorable -- e.g. trees on the O/H cables in storms, farmer ploughs up the U/G cable, "snow on the line", all of which have happened).
So maybe the vehicle battery solution might be OK. Or not?
http://www.apcc.com/products/category.cfm?id=13 shows several options. To select the best UPS for a five minute period would require you to aduit the total power consumption of the hardware.. For a 400W load with a five minute "up time", you'd probably need to look at something in the 750-800VA range.
As a side note, a friend in the back waters of Georgia runs his UPS of a car battery, and has done so for a number of years. Brown outs and power cuts are an almost weekly event down there !
Regards, Paul.