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How much back up a 650va computer ups can give for 12v adsl router

Solution
Computer UPSs are usually marketed as "10 minutes on batteries under full load". If your router takes 1Amp, this is 12VA power consumption, so (in the ideal world) 650VA UPS should power it for (650/12)*10 = 540 minutes, or nine hours.

I would rather "hack" that UPS, and power the router directly from the batteries (leaving the UPS internal electronic to charge it). You would probably need some simple voltage regulator between the batteries and the router, with couple of capacitors acting as a filter.
Depends on the battery size in the UPS and the efficiency of the conversion from 12v DC to 120v AC back to 12v DC, where you will see at least a 15-20% loss in electricity, but I would say about 2 hours. Keep in mind running a lead acid battery empty will pretty much kill it.

If you have the model of the UPS we could give you a better estimate.
 
If you has the 12volt battery directly it would be simpler because you are going to lose a lot because of the conversion. The percentage you loose is actually larger because you are pulling such a low load and there is some amount of fixed overhead for fans and such.

In a perfect world with no overhead you could get a couple of days if the router only takes say 1amp.

You best way to guess is to look up the batteries the UPS uses. For example if it uses 4 7.5amph 12volt batteries you would know you have 30 hours of power at 1amp at 12 volts with no overhead.

If the router is very low power and you have fairly new batteries I bet you can get 10-12hr out of it even with all the conversion to 120v and back. I know one I have that is about that size can run my tivo for over 12hrs.
 
Computer UPSs are usually marketed as "10 minutes on batteries under full load". If your router takes 1Amp, this is 12VA power consumption, so (in the ideal world) 650VA UPS should power it for (650/12)*10 = 540 minutes, or nine hours.

I would rather "hack" that UPS, and power the router directly from the batteries (leaving the UPS internal electronic to charge it). You would probably need some simple voltage regulator between the batteries and the router, with couple of capacitors acting as a filter.
 
Solution