i’ve been asked by someone on this forum to help them evaluate a “Microcar Virgo” as the basis for an EV conversion: he’s considering to put in a 90Ah LiPo battery pack in.
it’s similar to what you’re asking here so i’ll discuss it here.
MICROCAR VIRGO DIESEL HATCHBACK (01 - 03) - Premier TD 2 seat 3dr Auto Specifications | Technical spec, standard equipment, optional equipment, running costs and more - Help Find Me A .co.uk
so, the front surface area is 1.78sqm, and it looks (very roughly!) like a 0.35 drag coefficent vehicle.
now, the person who contacted me wanted to use a single-geared Lynch Electric Motor (LEMCO) which is a damn good “simple” choice, at 48V. the table from here:
L.M.C. Manufacturers of Permanent Magnet DC Motors - L.M.C Ltd Motors and Generators
says that at 48V the LEM-200 does 2500 RPM, and is rated torque of 35Nm.
also it says peak efficiency of 88%, so, knocking off a bit, let’s say it’s 85%.
tyres are R13 so that’s 0.33 metres radius.
weight is, let’s say… net weight is 400kg, 2 passengers 150kg, that’s 550kg.
ok! let’s plug those in, here:
Drivetrain Efficiency .85
Drag Coefficient .35
Surface Area 1.78
Rolling Resistance 0.007
Gear Ratios [1.0]
Axle Ratio 4.5
Max Rpm 2500
Max Accel 6
Max Power 10000
Max Available Power 10000
Peak Torque 35
Wheel Radius .33
and you get: max speed of 46mph, in 30 seconds, needing a peak power of 3.4kW to sustain 46mph. which is quite cute.
if you then plug that into the estimated “efficient” fuel economy figure of 0.28 litres per kilowatt per hour, that would work out aaaaat… 46 / (0.28 / 4.6 * 3.4) assuming imperial gallons 4.6 not hectares per potato U.S. gallons of 3.8 that’s a whopping 222mpg!
so yeah for goodness sake consider dropping in a 4kW small Diesel Generator in the back as well as a fast charger: don’t waste your money on a 90Ah LiPo battery pack, get a much smaller, lighter one and then you’ll no longer be limited on the range of the battery pack!
but yes: remember i’m guessing on that Drag Coefficient. absolute worst case it’s going to be 0.45 (most cars are between 0.25 and 0.45), which would put the car up to about 4.5kW.
for reference, the Aixam “NICE” Mega City Car uses 4kW @ 40mph and is pretty similar to what you want, similar drag coefficient etc. etc. in some ways, if 40mph is the target, you might as well just buy one of those