Someone has a drawing

?? Because I'm lost....
Power is the rate at which you use an amount of Energy.
To push a vehicle through air, and to bend the tires a little to make it roll, takes a certain amount of power. The faster you want to go, the more Power you need. The reason that you cannot ride a bicycle at highway speeds is because your body can't make enough Power to travel that fast.
So to be able to do the things you want to do with a vehicle, you need something to create the mechanical power to turn the wheels. In some places people use the term "horsepower" in other places they use the term "watts". These are different units that both measure Power. (1 hp = 746 watts).
In terms of electricity, there are multiple ways of creating the same amount of Power, since electrical power is made up the product of two things: Volts and Amps.
Volts * Amps = Watts
If you need 50,000 watts, you could get there by using 50 volts and 1,000 amps. Or, 1,000 volts and 50 amps. Or 500 volts and 100 amps. Or any combination of volts and amps that multiple to be enough Power. Electricity doesn't care. You can build a motor that would be suitable for any of these combinations.
However, there are inefficiencies in the wire that are not equal. The higher the amps, the more energy is wasted as heat. So, generally, to be efficient, we try to run at higher voltages and lower amps for the same Power target, to be slightly more efficient.
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I don't see why people are intimidated by a little welding. Is it even reasonably possible to build an electric vehicle without using a basic welder? There aren't really drop-in solutions from head to tail yet are there? Especially not with hacked bits of other vehicles. I suppose a clip-on part that locks the input shaft could be fabricated, but everyone's going to be using a welder anyway.