Now that I drive an EV around whenever I’m driving one of our ICE vehicles I like to think about what would it take to make this vehicle an EV?

Lets start with our new car: a 2014 Ford Escape. This exercise should be pretty easy as the Escape is based on the same platform as the Focus and thus shouldn’t require much more than the Focus. Looking at some of the specs for the Escape:

- 1.6L Ecoboost engine making 178 HP, 184 lb-ft of torque
- 3500 lbs curb weight

These numbers aren’t too much off from the ICE Focus (2.0L 160 HP, 146 lb-ft, 2950 lbs) thus to electrify the Escape: a slightly larger electric motor (just 20% larger) and more battery for the larger engine (about 30 kWh or so). The challenge with the Escape is that its footprint is about the same as the Focus which wouldn’t leave a lot of room for the Focus battery let alone a 30 kWh battery. It does sit higher being a CUV so there may be some room in the floor which isn’t available in the Focus. Note that using these numbers the converted EV Escape would still only manage about 75 miles on a charge since I’ve only extrapolated the numbers from the existing Focus Electric.

The next contemplation is a bit more, um, serious! Our RV:

- 6.8L V-10 engine cranking out 305 HP and 420 lb-ft of torque
- Weighing in at a hefty 12,000lbs

Now we’re talking large multiples (at least 2X engine size and 4X weight). Just taking that into account we’d need a 2X electric motor producing roughly 200 kW–or would the implementation be easier by just using two 100 kW motors: one driving each rear wheel. The real trick to electrifying the RV, though, is battery: This is due to the fact that for an RV to be useful you’ll want a ton of range (our RV has a 55 gallon gas tank giving it an effective range of about 600 miles). Simply doubling the battery size from the FFE won’t be enough, we’ll need something more like 10 times the battery size (due to the range requirements, and the additional weight of the RV). So now we’re talking about a battery around 250 kWh. How big would that be? Is it practical?

The best EV batteries today are about 240 Wh/kg (Tesla Model S). The translates our monster 250 kWh battery to be around 2300 lbs. That is a heavy battery enough so that our RV would have to bump up the chassis from the E-350 its based on to the E-450–it may also necessitate an increase in electric motor size simply to compensate for the additional weight (ok so lets put the motor at 250 kW from 200 kW).

Is there enough room in the RV for such a large battery? My initial thought would be yes: The electric motor can simply be bolted to the rear axle freeing up the engine bay, drive shaft tunnel, and exhaust pipe routing for battery usage. Again using the numbers from the Model S (about 700 Wh/L of volume) results in a battery that is: about 12 cubic feet in size. If we flatten that to a 1 foot high slab we get a battery that is roughly 3 feet by 4 feet by 1 foot high–easily tolerable in the RV.

If this appears all feasible how come we aren’t seeing ERV’s? Well something I haven’t mentioned, but also needs to be calculated, how much would a 250 kWh battery cost? A reasonable estimate for battery costs today is around $250/kWh thus a 250 kWh would cost $62,500 just about doubling the price of the RV–not including all the R&D that would be required for building something entirely new. Would someone pay that? If you were looking at two brand new RVs sitting on the dealer’s lot both identical to each other on the outside with identical floorplans inside but the left one had an electrical powertrain with a price 2X the one on the right with a gas engine would you purchase the electric one? (It should be noted that if there was a 3rd one with a Diesel engine its price premium over the gas engine one would be about 10% – 15%.)

Note that the numbers I came up with here are really just guesses (battery size and motor size) from scaling up the FFE’s motor–doing the *real math* to figure it out may come to significantly different values.

You forget to take into consideration the added weight to the RV would negate much of the extra range you would get. Then add a beefy charger for RV grounds, and the weight skyrockets.

There is a point of diminishing returns with battery weight. The next best thing would be to play around with a mix of lithium-phosphates and ultracaps. That would also be seriously expensive.

The added weight of the RV is attempted to be accounted for by having a battery 10X the size instead of simply 2.

In addition I did not address the fact that a 250kWh battery would take a lot of time to recharge using today’s Level 2 EVSE technology (most of which can provide at most 10kW of power). Like you said: The RV would require something akin to Tesla’s Superchargers to charge it back up in a reasonable amount of time.