I am reworking a rotating stage for a display case. I've attached a PDF of my circuit. The motor (which I am in the process of replacing) ran on 4 UV cells wired in parallel, producing up to 2.6 volts in that configuration. The motor needed 1.5 volts and could alternately be run on a AA battery. The new motor I am installing runs on 12 VDC. I have rewired the UV cells in series, so that they now produce a maximum of about 10.5 volts under optimal lighting conditions (i.e. shining a bright light directly on them). The problem is that these cells will be under different lighting at different times. My question is, how should I size the battery I add into the attached circuit?