# Motor and Batteries

• Electrical
Gold Member

## Main Question or Discussion Point

Hello everyone!

I'm doing a school project where we are responsible for designing a dragster race car powered by a small electric motor (1.5 to 4.5 V) h it seems to be called MOT12 (which I don't know the meaning of, it would be helpful if someone helped me understand).

We are allowed to power this motor using two AA batteries and I wanted to know whether I should try and find some 3.7 V batteries for the extra voltage or whether I should stick with a couple of generic 1.5 V ones.

I'm leaning towards getting some stronger batteries for the extra voltage, but how much a difference would it make, if at all?

On a side note: Any general tips on making an electric dragster car would be appreciated. I already have a general design, but anything is helpful (especially any info on how gear ratios work). The car needs to go 20 m.

I also wasn't sure where to put this I felt like DIY projects was also appropriate.

If there are no time limits, you should make the gear ratio between the gear on the motor and the car axis as large as possible, meaning making the gear on the motor as small as possible and the one on the car axis as large as possible.

CWatters
Homework Helper
Gold Member
Ideally you should use as high a voltage as possible within the rules.

However you may not need much capacity. Cheap unbranded alkaline cells from a $1 shop actually work better than say Duracell ecause they weigh less. However check the voltage on load. Do some experiments. Keep the weight to a minimum. Tom.G Science Advisor Cheap unbranded alkaline cells from a$1 shop actually work better than say Duracell ecause they weigh less.
True but... they also have much lower total energy. So if you need the maximum amount of capacity (total energy) per battery, get the name brand. For some uses, the cheaper ones can cost less per watt than the expensive ones, you just have to replace them more often. You could do the development using the cheap batteries, then when you are satisfied try the expensive ones and see if it helps or hurts.

CWatters
Homework Helper
Gold Member
+1 All true.

I was thinking for a dragster with a small cheap motor and short runs you are very unlikely to be able to fully discharge AA cells in one run. So why carry the excess weight.

Gold Member
So why carry the excess weight.
I'm actually leaning towards using heavier equipment to improve traction. We seem to be testing on particularly non-grippy surface, so I need that extra weight. I was thinking of adding some hot glue around the place to balance the center of mass and increase the traction of the wheels.

That is to say, I am looking at getting a couple of 3.7 V AA batteries and tesating (they are unbranded so I need to check whether it isn't dodgy). Also, I feel like the only forseeable issue is burning out the motor, but I'm only planning on 2-3 runs so that shouldn't be a problem. The motor is pretty terrible, I hoped I could get my own but I'm stuck with some unbranded stuff.