Im building an electric go cart. Can I use an alternator to extend my range, by adding charge to my battery?

Question

The cart has a "live" axle thats gonna turn anyway so why cant I rig a pulley to connect it to an alternator and use it to extend my range? I do not expect the cart to run forever, I know perpetual motion is impossible. I just wanna get a few extra miles per charge. I have been told it wont work can someone explain why?

Answer 1

If you only kicked it in for braking you would be ahead.

Answer 2

The battery provides a certain number of amps to make the motor turn to push the mass of the cart forward. Nothing comes free in the operation of the cart. The battery provides voltage and current that creates the magnetic field which cause the motor to turn. The alternator, even if the field magnetic force was supplied by permanent magnets would still cause the motor to demand more current from the battery to move the cart forward. The net output of the alternator would be less than the amount of power provided to it. What you need is a small gas engine that will supply the power needed to keep the battery charged. To find out what you need, you need to know the amount of power, in horse power, that the battery and electric motor produce, and size the gas motor to that amount of energy. If the electrics develop 3 horse power, then the motor needs to be a 3 horse power, 3.5 would be better to accommodate friction losses in the motor and alternator. Then you would have a system that would go farther. Using the axle as you mention to spin an alternator would have the same general effect on the cart as someone keeping the brake pedal depressed all of the time.

Answer 3

The problem is that you need to provide the energy to turn the alternator. The alternator will produce a huge energy sapping effect. You will have to provide the energy to turn the alternator, however you will also lose power in energy conversion. Most alternators reduce the peak power of an engine by 10 - 15%. Adding an alternator will actually reduce your range due to the energy it saps and the extra weight it adds to the go cart, as well as reduce the peak power your go cart is capable of producing.

Answer 4

You cannot create electricity from electricity. There is no such thing as a 100% efficient machine, so turning that axle will require more electricity than it can produce. If you add the load of the alternator, then your cart will consume that much more energy (i.e. it will be more difficult for the motor to turn and it will again consume more energy than it can produce).

I think the assumption you are making is that you can just add an alternator and it won't make it any more difficult for the motor to turn. That assumption is incorrect.

Answer 5

Sounds good on paper, but every time you transfer power from one form to another you have an imperfect efficiency. You will have to add a belt to drive the alternator which will actually slow you down. you will add weight to your car. Modern hybrid cars pick up charge as they slow down, but these cars are designed with cutting edge technology.