hi frnzs i'm new to this forum. can any one help me on this.

i want to design a backup circuit for a 12v, 5A, 45w halogen bulb. currently it is working on mains by connecting to a 12v stepdown transformer. near my home there's a frequent power cut. so i want a backup circuit for that light whn mains fail. and when mains come back automatically the light should use the mains supply and simultaneously the battery should be charge. and once it is fully charge should stop charging.

plz can any one help me on this.

 

Look here:
http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1824&appnote=en010951
Good application note for an intelligent battery charger.

Please don't E-mail and PM people to look at your thread when it's only been posted a few minutes.

 

sgtwookie, i just gone through the pdf which u've sent. but it is very complex. im just looking fr a simple one with out any computer interface

 

did you ever trying googling for a proper schema of ur choice.
Googling can give you enuf diagrams to go through, find one first and discuss it.
We cannot give you what you ask for if you are not willing to try to find it, we only share knowledge, the rest is up to you

 

I also hate using microcomputers when a dozen discrete components will do the job, but you haven't presented a float charger for us to comment on. Do your homework. Find something to start with. Give us a clue about what you have to work with, otherwise, you'll get answers like, "Go to Western Auto or Sears and buy a float charger".

I don't design things I can buy retail, because the stuff you can buy is cheaper than the parts it takes to build them! and faster, too. If you have nothing to start with, go buy a float charger. Otherwise, give us something to start with.