Exhaust fan battery backup

Anyone ever have a battery backup on their exhaust fan. I get the odd power outage during the winter and if the power is off for more then 30-60mins my house starts to smell and my wife begins to complain.
I'm looking for something to keep a 400cfm inline fan on for and hour if power fails.
Anyone ever try this?
Any ideas?

i had once hooked an APS unit with a truck sized battery to some backup lights and even a small tv. it was around 400watts or so, could power it for 6 hours straight, but the problem with those is that the batteries need some maintenance or else they will die quickly, and their cost will get too high. a car sized battery must be enough for your application. i have a 35watt fan, with this size i think that i can even go with a computer size ups with double battery size. Anyway, if i were in your situation, i would definitely seal the intake holes completely when the odd power outage occurs, and save myself all the money and hassle.

Once we had a hurricane and power was out for 5 days. Glad I wasn't growing at the time. Would have been disastrous. No question they would have molded up from the humidity with no fan, even if they survived the lack of light.

Something like this would power your fan for days...
http://www.ebay.com/itm/APC-BACK-UP...2103718&pid=100005&rk=1&rkt=6&sd=272385423362