Re-engineering diodes in a Battery Charger

I'm working on an old automotive battery charger that had no diodes to convert to DC. I made something from scratch, which ties (8) 4002 diodes to the back plate, and I am now getting 9.6 volts DC.

AC Output from the transformer is between 12.6 and 16 volts, depending on cycle and amp selections.

I'm not sure if I should use less diodes, or more diodes, to achieve 12 volt DC output.

Any insights would be helpful.

Thanks,
Gary

You need only 4 diodes to convert an AC soucre to a DC one. Google bridge rectifier.

Probably should be a 35A or 50A bridge, at that.

It would help a great deal if you could post some photos of the charger.