Power is the constant

lets just say you have a small and light conversion at 2000 lbs (and keep in mind your conversion is 2.3 times that weight.)

lets say you want to go 45 mph

It takes 12000 watts for example to hold 45 mph.

Thats 80 amps at 150V but 250 amps at 48v.

Ok not so bad.

Now you want to go 60mph assuming the correct gearing it would take 24000 watts to hold 60mph

160 amps at 150v

500 amps at 48v

Again on a powerlevel its doable (pureley power)

16 x 400ah 3.2V cells = 20KW

48 x 130ah 32.V cells = 20kw

Where you run into problems would be motor and controller ratings.

a warp 9 motor is rated at about 225 amps for 1 hour.

This means at 48v you can go about 40mph for an hour with good cooling before the motor is overheated (there are also efficiency factors at low voltages/rpms that hurt more.)

But at 40mph at 150V its way under spec (long life)

The same problem exists with the controllers. Their 1 hour rating is way lower than their peak advertised rating. For instance mine is 750 amps for 2 minutes, 550 amps for 5 minutes and 275 for one hour.

We are going for long life on the components (and a good top speed.) The compromise is higher voltage and thus lower amps through the motor and controller.

You are right its safer and easier (for you) but not for the motor and controller if you want to go much over about 35mph.