[pvusers] Need advice on using UPS as inverter

[Christopher Witmer <cdwitmer@spamcop.net>]

In Japan I have been having a very hard time finding an affordable DC-AC 
inverter; however, it isn't hard to find a large UPS that needs 
batteries. For example, I just found a used APC Matrix 5000 (a pure sine 
wave unit) now being sold for the equivalent of about $60. (This 
particular unit is being sold without batteries.)

This UPS is designed to work with any number of add-on battery packs, 
each 48v/17ah. (APC calls these "Smartcell" batteries and of course they 
have a multi-wire connector of a unique design.) Instead of the 
manufacturer's recommended battery packs, I want to use one BIG 48v 
battery string -- e.g., something in the range of 600-1000ah.

I imagine I will have to overcome two obstacles: 1) to get the inverter 
to accept a different battery than it expects, and 2) to recharge the 
battery string without using the inverter's built-in recharge function. 
(It takes eight hours for this UPS to recharge 10 battery packs -- just 
170ah. That means it would take 35-60 hours to recharge the large 
battery string I'm contemplating.)

I have access to a separate charger for the batteries, but does anyone 
care to speculate how easy it will be to get the inverter to accept my 
large battery string and function as I require?

Basically, I'm worried that the UPS might have some built-in self-test 
function and when it detects that something is not just as expected, it 
will refuse to function at all, and I won't be able to override or work 
around that.

Any thoughts? Thanks!

Christopher Witmer


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