Ideas on a Stir plate

From a hobby long since abonded, i would say some 14 years ago, i have some electric motors and servos and such for radio controled cars. How can i incorporate those items and a lovely magnet taken out of a transmission to make myself a stir plate?

I have a trickle charger and those old batteries for the cars, but i think the battery will only last for like 45 min to an hour based on low useage for the stir plate. How long does the stir plate need to run while mixing yeast? and hour? a day?

thanks in advance

I let my stirplate run a full 3 days, then put the flask into the fridge

I bet those motors and servos run on 6-18 VDC. You could get a "wall wart" type transformer to power them. This link will get you pointed in the right direction.