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#1

Hi all:

I want to build a 4 stage Auto battery charger.

1) Bulk constant current (say 4-8A) charge to 14.4V

2) Absorption charge at 15.6V constant voltage maybe 10+ amps

3) Float charge at 13.2V constant V.

4) Optional Equalisation charge at 15.6V constant V...maybe 10+ amps.

PiC based of course.

I've been looking at this sample

http://schmidt-walter.eit.h-da.de/smps_e/abw_smps_e.htm

But this charges an inductor which then discharges across a capacitor. This seems to be the accepted theory. But why can't I simply PWM drive the FET into a smoothing capacitor for basic ripple handling and then into the load. After all the load is a giant capacitor itself.

If I use a .1 ohm, 2 watt, current sense output resistor the PIC can throttle the PWM to the FET GATE based on an ADC sensed voltage drop to derive constant current.

Similarly the PIC ADC can sense the output to determine the PWM for a constant voltage. The PIC can then handle short circuit, no connection, and reverse battery voltage connection defense.

I want to build a 4 stage Auto battery charger.

1) Bulk constant current (say 4-8A) charge to 14.4V

2) Absorption charge at 15.6V constant voltage maybe 10+ amps

3) Float charge at 13.2V constant V.

4) Optional Equalisation charge at 15.6V constant V...maybe 10+ amps.

PiC based of course.

I've been looking at this sample

http://schmidt-walter.eit.h-da.de/smps_e/abw_smps_e.htm

But this charges an inductor which then discharges across a capacitor. This seems to be the accepted theory. But why can't I simply PWM drive the FET into a smoothing capacitor for basic ripple handling and then into the load. After all the load is a giant capacitor itself.

If I use a .1 ohm, 2 watt, current sense output resistor the PIC can throttle the PWM to the FET GATE based on an ADC sensed voltage drop to derive constant current.

Similarly the PIC ADC can sense the output to determine the PWM for a constant voltage. The PIC can then handle short circuit, no connection, and reverse battery voltage connection defense.