Controlling a charge to an SLA battery

[powderfish]

charge sla battery alternator

Hi!

I'm working on a project to use a micro to control the voltage and charge into a battery. I can output a voltage from a DAC controlled by the micro but I want to use this to alter the voltage and current supplied by a 15V DC source that can supply up to 3amps of current.

Ideally I would like to change the voltage delivered to the battery between 12 and 15V at currents up to 3 amps. It's a small scale version of intercepting a car's alternator output (in this case a bench supply) and modifying the voltage delivered to the battery controlled by the microcontroller.

The DAC is followed by an op-amp so I can amplify the micro's controlling voltage as necessary.

I have been playing with a modified version of a 2N3055 NPN transistor and LM317 circuit shown below, but i don't think I'm on the right track. For starters I have a DC input to the 2N3055 and I want to control the transistor using the DAC, not a resistor.

I would appreciate any ideas on how I can go about controlling this voltage to the battery.

Cheers,

Powderfish

 

[wizpic]

Have a look here this does what you need
#1187805

I know that it uses amega 8 but the rest of the hardware will do what you need,I'm sure that aq_mishu would not mind using his hardware,

I would say you would need around 18V-20V to charge a 12V battery if you wanted to use the drawing then use a 4K7 inline with the emiter of the 2N3904 and then connect this to the MCU and use PWM to control it. but I'm sure this will only control the voltage and not the current where I think that aq_mishu's design you can control the curent limit and voltage