# COMMUNITY : FORUMS : TECH

## 12V DC to 220V AC supply

hello
I have a emergency light with battery back up. its lights have gone out so i want to use its 12V dc power to transfer to ac power to backup a media converter, wifi router and mobile charger. Please, i want a detailed process of building this system. how much time could i get backup? i need a instrument and parts list for this project. i have uploaded the pictures of my light and specifications along with it.

thanks

cerez3 years ago

it seems you are looking for the inverter. So generally let us
start from the power requirement. First of all calculate the total power
consumption by your devices that you want to operate let us assume it will be
100W and you buy a DC battery of around 600W. So the most important thing is
transformer if you will use the transformer of rating 12V, 2A (24W). Then your
battery will last around 25 hours and if it is of rating 12V, 10A then the
battery will last around 5 hours, so this is how power rating of the
transformer decide the time the battery will take to discharge. So if the power
consumed by your appliances is 100W you must choose the transformer of rating
at least 100W and your appliances will work till 6 hours. The circuit diagram
of the inverter is easily available over internet.

mpilchfamily3 years ago

Buy a car inverter and connect it to the batteries and your done. Make sure the inverter is able to support the power draw of all your devices otherwise you'll blow the fuse on the inverter.

With the batteries being rated at 7.5Ah they will last about 20 hours at a current draw of about 7.5. Being that they are older, you can expect a much shorter time frame.

Key here is to figure out the peak power draw of all the devices you want this system to support. Then you can figure out how long it will last and how large an inverter you will need.

3 years ago

A 400W or larger inverter should cover your needs. Impossinble to tell how long it will last. You'll have to put it all together and see what happens.