How to build your own battery backup in case of power outage?

[sillybillygum]

I have frequent power outages and really want something to keep the exhaust fan running for smells and power a cfl bulb to preserve light cycles. I was thinking about a car battery hooked up to an inverter. Could I just keep adding batteries in parallel to add more run time? How would I calculate run time at a given wattage? My main concern is how do you make a switch that senses when main power goes out and switches to the batteries?

 

[DonkDBZ]

Honestly its cheaper just to buy one from Frys or Best Buy. A 1000VA UPS will give you 500 watts to burn. so you could have 2 25watt bulbs on for 10 hours. Plug the UPS into wall timer into UPS then bulbs into timer set to same schedule as room.

Otherwise you will need a AC to DC inverter. A Circuitboard to wire up so u don't overcharge the batterys then a DC to AC inverter to power up your stuff.

The since switch is easy. Use a relay with a 120coil. Wire the coil to the circuit with want to sense before any timers. Run the Hot from the battery to a Normal closed contact. As long as power is on the coil will be closed which means the battery contact will be open. When power shuts down the coil will open and return the contact to closed completed the circuit for the battery.

 

[ogatec]

the problem will be the exhaust fan. even the smallest motor is gonna eat up the juice. how long does the power stay off? yu might think about a portable camping generator..the smallest ones sound like a loud weed eater when in use & would provide plenty of power for fans & even a hps lamp...

 

[homerjay]

Ever look into the UPS that they use for computers? I ask because I never have. Do they have the wattage you need?
Now I know what my next Yahoo search will be.

 

[ChaosCatalunya]

Computer UPS may well be the best option, clever people may well know how to daisy chain them, some may even have that function, but there must also be Server UPS available with much higher specs. Kicking in an emergency Generator is a function some will either have, or it can be built in, like in friends panel-battery/inverter-generator solar setups.