[IamIan]

Given the known differences in Weight , Aerodynamics ,etc.
Between the Leaf & Gen1 Insight:

no wind , flat level ground , Standard Temperature , etc.

Including the rolling resistance effects of a 1550lbs + 750Lbs = ~2,300 Lbs BEV-Insight Conversion.

Including 250Watts of DC-DC 12v system load

Includes if motor controller and motor combined are ~90% efficient .. ie what the batteries would have to put out.

Nissan Leaf (~roughly):
~11.95kw to sustain 60MPH @90%Eff = ~13.28
~7.9kw to sustain 50MPH @90%Eff = ~8.78
~4.97kw to sustain 40MPH @90%Eff = ~5.52
~2.93kw to sustain 30MPH @90%Eff = ~3.25

The Gen1 Insight Need to supply to wheels:
~8.80kw to sustain 60MPH @90%Eff = ~9.77 = ~36% further than Leaf per kwh
~5.95kw to sustain 50MPH @90%Eff = ~6.61 = ~33% further than leaf per kwh
~3.87kw to sustain 40MPH @90%Eff = ~4.3 = ~28% further than leaf per kwh
~2.42kw to sustain 30MPH @90%Eff = ~2.69 = ~21% further than leaf per kwh

I don't know the average ICE efficiency you get when you get that 80 MPG ... but here are some comparisons.

Worst case ... if you were getting 100% ICE efficiency ... you would be getting about ~2.3 miles per kwh.

At the highest ever quoted Gen1 Insight ICE modeled efficiency .. form EPA420-D-04-002 ... peak LeanBurn at ~48% ... you would be getting .. ~4.7 miles per kwh.

At 35% ICE efficiency ... you would be getting ~6.5 miles per kwh.

Although your ~80MPG rate of energy per mile would likely decrease with the additional vehicle weight ... you could test by driving around with about ~450Lbs of passenger+cargo weight.

However ... I think if you continued the same driving habits , and conditions ... over 5 miles per kwh of battery is a safe / conservative estimate .. and up around ~6 miles per kwh of battery is perhaps a bit optimistic.

It is also a good idea to include some safety margin in your battery pack design ... for cold weather .. for unexpected detours ... etc .. **** happens.

I would recommend about a ~25% additional safety buffer margin.

For 150 miles .. that would mean you will want a minimum of about usable 30kwh.

For 200 miles ... I would estimate you will want a minimum of about usable 40kwh.

If you can to opportunistic charging ... Than you could vastly reduce the size of your needed usable kwh of battery pack ... sometimes by 1/2 , depending on your situation.

Looking at acceleration rates for the ~2300 Lbs Converted BEV-Insight.
3 m/s^2 rate of acceleration 0-60 in about ~9s ... would need about ~60kw for those ~9s.

I would recommend Batteries , controller, motor should all have a ~10second Max rating of at least (minimum) +25% .. or ~75kw peak ~10second Surge rating.

I would also recommend not going any lower than about ~30 kw sustained / continuous duty rated equipment .. that should still give you a little safety margin for daily non-flat conditions.

A good bit of the Leaf Pack weight is the structure the way Nissan did it ... You can probably package significantly better ... Each Leaf 4 cell subpack module comes in at about ~125 wh/kg ... 30kwh worth of those modules weighs .. about ~240 kg (~528Lbs) .. +you will need to add additional weight to that for connections , structure , etc .. of a final complete battery pack.

Leaf packs are nicely .. fairly easily available .. and nicely low in $/kwh ... but if you are willing to pay more $/kwh ... and do more hunting for the less commonly available .. the Tesla packs have far more wh/kg .. ie .. same kwh weigh less:

For example .. Tesla Cells come in at about ~265 wh/kg ... a 30kwh pack would be about ~114kg (251lbs) worth of batteries ... +you will need to add additional weight for the connections , structure, etc ... of a final complete battery pack.

I would also strong recommend testing any cells you get ... it is only the 'usable' capacity that is of value to you .. if some old junk yard Leaf cells only give you ~120wh/kg , than that is what they are ... and if some old junk yard TeslaModelS only gives you about ~250wh/kg output from it's cells .. than that's what they are ... don't just assume they will be a 100% perfect fit to published specs ... or to the test results others have gotten.