I've made a small solar panel array(six panels 0.3 watts each, 3.6 volts each). Sometimes I may want to charge two batteries and sometimes four. So am I correct in assuming that if I have a 4xAA battery holder, and I place two batteries in it, the circuit will not be complete and they will not charge; and if this is so, could I use some sort of jumper between the two empty slots to complete the circuit(it sounds like even if that worked energy would be wasted on the empty slots with the jumpers in place, no?) So would I be better off attaching a set of two 2xAA holders with a dip switch or something? Any help is appreciated.

just bridge out the other 2 slots with a couple of dummy batterys,

as long as you have 3.6 v over the 2 baterays in series then they should charge,

you need about 6.4 for 4 batterys,

or conecct 2 sets of 2 in parrelel

Thanks for the reply. The solar cell yields a total of 21.6V and 1.8W so I'm not worried about that aspect, I was just curious if energy is being wasted if two slots of the 4xAA holder were not holding batteries to be charged, but were just being bridged to complete the circuit; if so it seems like it might be better to use two 2xAA holders and a dip switch.