Battery power?

Question

I have a go-kart with 8" rims. It weighs 300 lbs without the motor. If I wanted to turn this into an EV, how powerful of an electric motor would I need? Would 7 hp be enough? I want it to be really powerful. How many car batteries would I need to power the motor for 3 hours considering I will be driving it pretty fast most of the time.

Answer 1

I think 7HP is much more than you need. 1HP is probably more appropriate. You're starting at a major disadvantage. 300 lbs without motor, battery, or driver is very heavy for an EV. You'll never get enough battery into it, especially with standard lead-acid car batteries. You don't want those anyway, you want at least deep discharge RV/marine batteries, or a much more modern chemistry. See the first reference and look around it. The commute car is very high performance with a very good range. But it costs in the ten-twenty thousand dollar (US) range. For the ultimate, see the second reference. It's real, I know the people. But the price tag for the first generation is US $100,000.

There's a good reason electric cars are not yet common. The enabling technology is just now being developed. With further development and volume manufacturing, the prices should drop considerably.

My son has a new electric bicycle. It's very practical for commuting, but the cost is still around US $6000. Good range and speed. It keeps up well with expressway traffic.

If you just want to play around, get the biggest standard RV/marine battery you can, and a used auto starter motor from a junk yard. Get a few, since you'll probably burn them out. You probably can't afford to play around with gears or electronic motor controllers, so just gear it for its top speed of maybe 5MPH and use a very heavy duty foot switch and/or use the starter relay. It won't be a smooth start, but it would work.

Answer 2

No, if you have the external power plugged in, the laptop will run off the external power while maintaining a charge for the battery. The natural fall-over is from external to battery. I am not sure why you would want this, is AC power is available for my laptop, I am sure not going to use the battery.

Answer 3

Look into the possibility of using good batteries if you plan on using it often. A motor and battery pack from a prius might be a good answer. The prius uses regenerative braking also.

Answer 4

7 HP should move you fine. Now do the horsepower-watts conversion and determine the power needed in amperes to generate that power, determine total ampere-hours needed and size your (very large collection of) batteries accordingly.

Answer 5

Have someone push you