smart battery charger circuit

[--BawA--]

i have to design a battery charger for 65AH 12V SLA battery, it should start the charging in BULK mode to 14.1V and after that it should trickle to 13.65V. i want to use microcontroller to monitor all the parameters, i have variable DC source which is capable of providing a voltage from 12V to 20V and 10 ampere current , so how to start with? i dont have much idea ,so plz give me some link or application note.

 

[chuckey]

First you must measure the voltage and the current. You must build some interface to be able to control your PSU output voltage. So I guess you will need two A to Ds and one D to A.
Frank

 

[--BawA--]

I have to charge the battery at 6.5 ampere current .so how to limit this 6.5ampere current from microcontroller..i'll be using pic18 series mcu.

 

[schmitt trigger]

Below are the required steps. The actual code depends whether you are using C, Basic, Assembler or something else

0) Initialize control variable to PWM timer or the DAC to a low value.
1) Sample current, condition sample to within a 0->5V range
2) Perform ADC conversion
3) Compare ADC value against value in setpoint variable
4) Adjust the control variable up or down as required.
5) go to 1), repeat forever.

 

[chuckey]

Just increment the output voltage and measure the current, when the current hits 6.5A, stop incrementing the voltage!
Frank

 

[--BawA--]

anybody knows any P MOS of specification 20 ampere (or greater) drain-source current and capable of handling around 50Volts atleast ,,? i have to use in the buck converter to charge the battery rated 12V,65AH. ,,also it should be easily available??

 

[ZASto]

IRFP9140N or IRF9540N