Google "boost converter".

I doubt you are going to get anywhere close to 40 KPH with a 3 HP 220 VDC treadmill motor.

For what its going to take to make a converter to run it off of a 24 volt battery bank you will be time and money ahead to just go online and buy a stock 24 volt DC motor and be done with it.

FWIW there is a lot more to building a gocart than just saying I have this motor and I want to go this fast.

Sorry but you needed to know.

3HP * 746W/HP ~= 2240W. Divide that by 24V means your battery would need to supply ~93A, taking into account conversion efficiencies that'd be > 120A. That's a lot.

Also your motor isn't rated for continuous duty and neither are your batteries, so they're not suitable for the job.

It's going to be way cheaper to get another (24V) motor.

3hp motor at 24VDC will still draw the same amps!

I've not bothered to calculate the energy conversion to see if you've inadvertently asked for more power than is possible. I will ask for a key clarification though. Do you want a generic circuit design of individual transistors, resistors, capacitors and transformers to do this or are you looking for block component names and parameter values that will allow for this to be attempted?

Let's see. 3 Hp or bigger gas engines are available used for a song. They are always ready, and function reliably as long as they are fueled.

And you want to replace it with what? Batteries delivering continouos current of a starter motor of a smaller car. For how long? You got to be pulling my leg.

The motor is not built to shed excess heat for any length of time. Burnout is under a single minute, I guess.

You want to go racing with it. The opponents will fall out of the seats laughing at the Rube Goldberg setup. Buddy, you asked for it by not even doing a back-of-the envelope estimate, or some basic tests before piping up. Some testing, any testing on your part would show at least good faith effort.

hmmm, E-Bikes use 500W motors and claim over 20km range.

3HP with some big old cranking batteries could go like stink for a few laps!

(as long as the total weight is low).

I would design for 200% current for about 1 minute just for the fun!

We see again the problem of electric cars! Too little power density in the batteries.

Too little power density in the batteries.

more like too little power density in lead acid batteries.

I spotted this bit of alternative EV fun this morning.

First 10 feet I believe. The finish I think was staged.

Turning some old cranking batteries into a bit of fun is commendable. Are you sure they're still good (good enough)?

I hope you haven't bought that motor yet.

I agree with the others - this is not the way forward.

All through your system there are losses which will appear as heat as you make conversions.

I'm convinced the motor is not the right one for the job. Its not rated for continuous duty.

If you are really determined through what about 220V from a string of smaller batteries. Be aware though that DC is scary stuff and not the easiest to switch.

A lawn mower engine would be a great improvement on your DC motor.

DC motors have their applications but this isn't one of them.

I think this is a great project. It will be fun but you will likely have a few failures along the way.

There are a couple of things you should watch out for, Get a breaker to protect your batteries (shorting them could be dangerious), install a big diode accross your motor leads to prevent switching spikes and if you can get a motor with a voltage in the same range as the bateries then you won't need a DC-DC converter which adds another layer of complication and expense.

Here is a converter example http://zahninc.com/su13.html

Good luck and have fun!

What happened with this idea? Is there some reason you feel compelled to mismatch battery and motor voltage?