[REQ] a battery backup with charger

[riteshjain_82]

hello

Actually i have a system which is working on 12 v dc
i want to attach a 12v SLA battery so that it shift automatically on battery if case of mains failure without resetting the microcontroller
Also the battery should charged automatically when the mains is present. i want to use 12v/7ah(ups type) battery

thanking you

[jestanoff]

Look at this aplication note:
http://rapidshare.com/files/273903282/Battery_Charger_for_SLA__NiCd.pdf.html
If you use for your project figure23, simply add voltage regulator for microcontroler directly to the SLA battery.
Enjoy

[riteshjain_82]

This limit is reached.
pls upload again

[jestanoff]

http://www.megaupload.com/?d=6MOD4N9L

[Jehan]

You should use an smps based charger for your 12 volt batery, the 12 volt battery output will be 13.8 volt when it is fully charged, you will have to use a switching   regulator to bring the output to 11.8 volt and then OR this 11.8 volt thru schottky diodes with the 12 volt input system.

as the battery output is set 0.2 volt less than your main input of 12 volt the main input will be supplying the power. when the main input dips below 11.8, the main input OR diode will be reverse Biased and the power will be supplied from the battery.