Here is a tried and true Home UPS Approach.
We used it for seven years on a Web Hosting Start-up.
We ran 4 servers 24-7 for seven years.
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Simple::
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We used two Heavy Duty Deep Cycle Batteries (the kind they use in Large Diesel Tractor Trailer rucks).
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We used cheap DC/AC Inverters (Harbor Freight $79.95).
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We also used simple Battery chargers.
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Each Computer/Server was hooked up to a UPS. The UPS was powered by a set of Batteries. The batteries were hooked up to a battery charger.
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I told you it was simple!!!
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Background:
1st: A 24VDC or 48VDC Computer/Server Power supply is expensive.
Normal AC Powered Computer Power Supplies are not.
2nd: Commercial UPS's are expensive... Most home UPSs (the $299.00 variety) only give 10 to 15 minutes of back up power.
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The simple set up I described would easily power the server for over 48-hours with a sustained power outage. Since it was hooked up and always on-line, it was essentially a 24-7 power source for the server.
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We have since migrated to multiple Blade servers in a custom built Server center. Our server center has three phase power, and we use a set of 100KW Commercial UPSs. But they are nice, but cost per KW - the Battery and Inverter with Battery charger was the most economical all around for a server, or even a pair of servers. But our operation has grown to over 28 Cabinets, each with at least 64 Blade Servers - way to cumbersome for dedicated Batteries, Inverter, and Battery Charger for each Blade Server Set.
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Dave
Phoenix Computer Labs