Lately I have been trying to get my charger to work on DC current, but it doesn't seem to work right.

When I connect it to my car battery, the measured output current is about 1/4 of what it is on equivalent settings when connected to 120v out of the wall.

Also, I have converted an old pc power supply for use with chargers. It is supposed to put out 8 amps on the 12 v line, and when I connect an automotive bulb to the 12 volt output it is extremely bright. However, when I connect the charger to it, it turns on but will not charge batteries whatsoever.

Is my charger broken? Or is that just the way the superbrain works (or doesn't...).