UPS recommendations for 1 PC + router

sajunky said:
Guys, if you want to backup DC-powered devices like routers, don't do it with UPS. It is very inefficient, particularly on the light loads. Use DC/DC converter and power it from the old car battery (which is no longer able to crank the engine), or drill a hole in UPS enclosure and take power from internal UPS battery.
You can get 90% efficient DC/DC converters, even though standard USB 5V/2A cigarette car chargers will do.
To supply 12VDC devices there is less variety devices, as it requires mixed step/up step/down design, but you can use two 12V batteries in series when is no other choice.
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Will something like this work with a car battery hooked up to it? It still does all the protection and then you run straight off the 12V output.
 
In that case you might as well connect one huge-ass 12V battery direct to the modem. You would use that power supply purely to charge the battery...
 
furpile said:
Will something like this work with a car battery hooked up to it? It still does all the protection and then you run straight off the 12V output.
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Yip, very nice. It doesn't say lead-acid battery, but output voltage on the battery output is right and there is battery cut-off, so I assume it has full charging control.
Many times to much power for single modem/WiFi router. :)
Just connect battery to output 2, adjust voltage on output 1 to meassure 12V and connect your equipment.

Maximum charging current is right for typical 7Ah battery. If you use car battery remember that every few months it is good to remove it from UPS and do refresh cycle using nominal current for that battery.
 
sajunky said:
Yip, very nice. It doesn't say lead-acid battery, but output voltage on the battery output is right and there is battery cut-off, so I assume it has full charging control.
Many times to much power for single modem/WiFi router. :)
Just connect battery to output 2, adjust voltage on output 1 to meassure 12V and connect your equipment.

Maximum charging current is right for typical 7Ah battery. If you use car battery remember that every few months it is good to remove it from UPS and do refresh cycle using nominal current for that battery.
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Cool thanks. Getting a second hand 45 Ah battery from work for cheap, will hook that up.
 
On second thought: I would extra check whether output voltage is regulated in backup mode (AC removed), as if not, it would restrict from using some devices, i.e. 3.5" portable hard drives. Pls let us know, I am interested.
 
sajunky said:
On second thought: I would extra check whether output voltage is regulated in backup mode (AC removed), as if not, it would restrict from using some devices, i.e. 3.5" portable hard drives. Pls let us know, I am interested.
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Yeah I'll get some advice from electronics guy and see if it will work.
 
I've always thought a UPS is purely to keep the system running while it automatically shuts down - so a 10-15 minute time. My uncle says he got one that lasts for 5 hrs + ... ?

They exist ?
 
Dolby said:
I've always thought a UPS is purely to keep the system running while it automatically shuts down - so a 10-15 minute time. My uncle says he got one that lasts for 5 hrs + ... ?

They exist ?
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Yes, depending on your budget. A UPS does 2 things usually, regulate the power supply to protect against over voltage, under voltage etc, and supply backup power to keep the system running if mains power is not available. This is usually supplied by a battery. If you make the battery big enough you can keep the system going for however long you need to (although the charging side has to be able to recharge the battery again). Most UPS's are rated in VA (basically the power it can deliver), so the higher the VA the longer it can run. Getting a UPS to run a high end PC and screen for 5 hours is gonna cost you though.
 
Thanks furpile!

I'll check on sizes and prices
 
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