A while ago I left a comment on a Timbuktu post
on making a UPs from widely available materials and noted that I was not sure whether this was a viable proposition.
I have since had a look in South Africa and found the following prices, for the equipment used in the design the post reported on.
battery 100 Ah R 1 240
charger 685
invertor 800 W R 1 450
plug strip 60
I must say the prices seem to be rather variable so I have taken mid range ones.
So its going to cost us R 3 400 to put this together and we end up with bits and pieces that take up space.
Commercial UPS come at different prices for different specs but give you something with a sealed battery in a single box that can sit under the desk.
In South Africa I found:
Numeric 15Ah 800W – R 800
Mercer 20Ah 600W – R 2260
DTech 104Ah 600W – R 5500
So prices are very variable, both the wattage and the battery capacity effect the cost strongly, but its hard to compare directly and accurately.
I would expect you get more with a complete system eg control software, system guarantee, more plugs and cooling for maybe a little more than making your own.The profit for the manufacturer must reduce the benefit of buying in bulk.
So it is viable to put together your own system and the original article was anyway interesting in the background it gave.