Julian,
My question is : do you want to study
only very high powered electric car ? Or do you give numbers about these sort of cars because you don't find others ?
So you want a percentage of the total drag.
This value will be high for a (very) high power car having a low cd and no front shutter. Some Tesla model for example. Without grill shutter they have to handle the worst case possible: a lot of air goes always through the front grill.
At the middle you will have a lot of cars where makers don't give data. Today you can find Cd, it is more difficult to find frontal area, but cooling drag never.
Some guys in priuschat forum have tested blocking totally the front grill. I remember 4% cd decrease.
Here they found 3%
At the low side you will find low power (Or medium powered used at low power) car
with grill blocking for which during most of the time the cooling drag will be near zero. The drag losts will depend upon road conditions. This drag will increase if you climb stepped hills and get some energy back going down (What ice don't do)
And at a very low side your bike that have a tiny cooling drag.
This study show cooling data.
Of course you don't have the exhaust pipe and his cooling in BEV cars.