Solar car, Voltage determines Velocity

Thread Starter

Caters Carrots

Joined Nov 9, 2016
I have come up with an idea for a solar car. Now I am not going to build it because it would require welding and although my dad knows how to use a welder and a plasma cutter, I still think it would be too dangerous for even my dad to build, not to mention expensive. Even if he cut all the metal himself, the metal would be expensive. Not to mention it could start a fire which would mean no more solar car.

But just because me and my dad can't build it doesn't mean I can't come up with an idea for it. So here is my idea. I was thinking that maybe voltage could determine velocity.

When the car is charging, it is connected to a solar panel via a cord which plugs into the top of the car. Then, wires within the chassis send electricity to the battery to charge it up. Once it is fully charged, it won't overcharge.

There are 4 different situations that can happen with the battery based on amperage and voltage. Those are:
  • High voltage and High amps(doesn't need recharged)
  • Low voltage and Low amps(needs recharged)
  • Low voltage and High amps(needs recharged and is being used a lot(that or resistance is too low)
  • High voltage and Low amps(Resistance is too high, even the high voltage can't overcome the sheer resistance)
So anyway, I know that the circuit would be a lot more complicated than I am showing in the image but it will be easier to understand this way and just so you know, I am using electron current(the true current) so polarity being backwards is because of that. Electrons flow from negative to positive. A big misconception to physics students is that positive charges move but they don't, they are too massive. Conventional current though forces students to think backwards is forwards. This world would be a much better place if we just used electron current. Then there wouldn't be this "positive charges move" misconception.

Anyway, here is the simplified circuit(this actually is the original circuit, I will draw a more complicated one just to show how complicated it is):

View attachment Basic car circuit.pdf

From the negative terminal, through the negative wires(those black wires), the electrons flow to the 2 motors(LM means left motor and RM means right motor) and the built in multimeter. Then they flow through the positive wires(those red wires) to the positive terminal. This is all in terms of electron current(here negative wires to negative terminal makes perfect sense).

As the voltage on the motors increases, the speed increases.

If the voltage difference is 0, the car goes straight. If it is non-zero however, there is more of a torque on the motor with more voltage. Since the motors are mechanically connected to the wheels, this also means more of a torque on the wheels that are on the same side as the motor with higher voltage(so if the right motor has a higher voltage, the right wheels will have a higher torque and thus a higher rotational speed. And while individual torques on the wheels may cancel out, there is 1 more torque caused by all these other torques. That is a torque on the entire car. This 1 torque(which remember originates from the voltage difference), determines whether the car will turn left or right and like the wheel torques, is also in the direction of the higher voltage(so if the right motor has a higher voltage, the car will turn right).

What do you think? Is this a good idea as to how voltage can determine velocity?


Joined Jan 15, 2015
What do you think? Is this a good idea as to how voltage can determine velocity?
What do I think? I think every engineering enthusiast starts somewhere. :) Here is what I would suggest. You may want to start with doing a little homework (study) of how electric cars actually work and what is involved between electrical energy and actually making the wheels turn. You may also want to think about how much power is involved to move the weight of the car. While solar is a nice concept you may want to look at the roof space and just what you can get with solar panels to charge your battery. I won't tell you that your idea won't work. I will suggest more study and just getting the basics understood. :)



Joined May 4, 2013
Good advice from reloadron. I would add that you could also learn a lot by building a model car. It won't cost as much as a full size car and no welding. :D

Be warned. Your model likely will not work very well. This does not matter in the slightest. The goal here is not to put the car manufacturers out of business. ;)