Science Buddies: "Ask an Expert"

Hi, my son has been working on the light tracking robot for his science fair project this Friday. He was trying different sizes of batteries to see how they affect the speed of the robot. We were having problems with the motors going constantly, even in the dark. Then we somehow got them working and tested the robot with AAAA batteries. He switched out the AAAA batteries, and put AA batteries on. Now we're having the same problem with the motors going constantly and can't figure out why. We've checked and re-checked everything, and aren't seeing anything wrong! Please help! Thanks!

That sounds like you may have some kind of intermittent short or open in your circuitry somewhere that is affected by changing your batteries. I would try jiggling all the wires, rotating the batteries, checking your connections with an ohmmeter, etc., etc.

There should be no difference between the 2 batteries in terms of power (assuming they are the same "type" and brand/quality, e.g. all alkaline Duracells). You could get difference results with rechargeables or lithium batteries, though.

The only thing that should change between AAAAs and AAs is the length of time it works.