William this can be done in a few ways, but it would be helpful to know the specifics of the charging circuit. 12VDC in and ? out. Is it a switching supply? At these voltages and stored charges , You want to be careful what You do The best at overcharging you can expect is a lot of smoke and some expensive caps that are trash, the worst ..well not good. Normally regulating circuits are based on current draw of the load.
I assume that your using a DC V at higher then the rating of the caps , hence the quick charge.
More info would help