This was never going to be a cheap project, and I know it. The money is often the most frustrating part for people who want to do an EV conversion, because you never think it should cost this much. It was that way for me too. I’m an engineer with a family on an engineer’s wages, there is no trust-fund, so all of this has to make genuine financial sense and it has to be done by thinking things through. I can’t just throw more cash at it.
As described on the home-page, part of the intent here was to have an EV that can compete with an average gas-powered car on the cost-per-mile. That’s a stretch, and it all depends on how you calculate things. For my project, I looked at the cost over the course of 6 years of owning and commuting to work. I drive 260-or-so miles a day or 65,000-70,000 miles (100,000 km) per year, and 6 years is ~400,000 miles.
Driving 400,000 miles means that all of the moving parts have all been replaced at least twice, and by this point the insides are pretty much done too. To make a car go beyond 400,000 would mean a complete rebuild / restoration, so (for me) that made 400,000 a reasonable end-of-useful-life marker for any regular bought-at-the-dealer car. So, this whole project has to pay for itself within those 400,000 miles.
First thing was to pick an average car to benchmark things against. Looking at durability, gas mileage, a decent front seat (I’m 6’8″ tall) etc etc, I ended up with a unspectacular Nissan Altima SV bought at MSRP of $20,000 all-in. From there I made a bunch of assumptions around how long things would last (200k miles for a transmission, 150k miles for an engine, 30k miles for a set of tires, 100k miles for things like shock absorbers and on and on) and I calculated the cost of the car itself, the maintenance, the repairs, and the gas it would use (at $3 per gallon). All in, top to bottom, it comes out to ~$0.38 per mile to get home from work, excl. insurance and registration.
Next I compared this with a similar-size factory-built EV. In this case, a Tesla model S with a purchase price $120k all-in. That car had just been introduced when I was doing this pre-work on this project, and no-one at Tesla / the dealership would even venture a guess on whether it would do 100,000 miles w/o any major costs, let alone what this car would do around 200k, 250k miles (mid-way through the required lifespan). Would it hold up, would it need a new battery pack or new <something>, nobody was willing to even guess. So, I’m adding financial leeway to have something horrible happen once, say around 250k. With that assumption, and after adding in the maintenance, tires, repairs, wear&tear parts, the electrical bills etc, the bottom-line cost number comes out to $0.57 per mile. That’s 1.5 times what the Altima would cost, and that doesn’t sound unreasonable when you consider the price-delta between the Tesla ($120k) and the Altima ($20k). It’s actually pretty good.
So, that’s what started me down the path of building my own EV. If the most professional, most solid EV on the market can’t even come close to an Altima, how are the lighter ones going to stack up? Most don’t have the range I need, the life-spans are a complete unknown, and in the end the Altima’s $0.38 per mile is surprisingly hard to beat.
The math on the Cadillac goes something like this.
The basic car comes off of Ebay, and a not-too-rusty example is ~$7,500. The engine is either missing or seized up, the interior is toast, no brakes, all of the specs of a typical project car. To restore that car into something shiny takes maybe $22,000. There’s no engine/transmission work, $5,000 for a new interior, another $5,000 for chrome, $1,500 to powder-coating the frame, $2,500 for brakes and suspension parts, $1,050 for a set of tires, $7,500 for paint, the list is long but it’s not too bad if you do the work yourself. All in all, the cost of a nicely rebuilt 1959 Cadillac sedan is (was) around $30,000. Ebay’s buy-it-now prices did more or less confirm that.
Then comes the conversion.
The motors are listed at $2,500 each, and the controllers are around $3,500 each, plus the adapter plate & work to tandem them, comes to $14,000. Add the 2:1 gear reduction box at $4,500, a parking pawl for $500 and some custom motor supports for $500, and the entire conversion of the drive train comes in right at $20,000. The estimated life-span on the motors is 10,000 hours (seriously) and at 2 hours each way that’s 2,500 days so 10+years / 2 life-spans. The gear-unit and the controllers are longer-life than these. So, half of this cost per 400,000 mile life-span seems fair? at $10,000.
The batteries last 2,500 cycles. That sounds like a lot, but it isn’t. I’d have to charge each night to get to work, and each day to get back home. That’s 10 cycles a week, so I get 200-400 weeks’ of use. That’s 4 years on the conservative side, or 7-8 on the optimistic side, so I’m going with 1 battery pack for the 6-year, 400,000 mile period. Right now, the cost of a 100 kWh battery is (app.) $225 per kWh so $22,500.
The accessories like pumps and AC and all that adds up, not because it’s that expensive but because there’s a lot of little pieces. Right now I’m halfway done and about $6,000 in, so let’s estimate $12,500. Then there’s a charging station on either end of the drive for $2,500 each, and I’m sure there’s small-stuff that I have forgotten along the way.
It adds up to $30,000 for the car, $20,000 for the e-drive train, $10,000 for the conversion-parts, $22,500 for the battery, $12,500 for the accessories, $5,000 for the charging stations, and 10% for unforeseen(?) = $110,000 for an electric Cadillac.
The comparison
From there I add in the maintenance, the tires, the repairs, all per the same logic as the other 2 cars, and I compare the end result. To drive 400,000 miles, it’ll cost me:
- $145,000 using a Nissan Altima, $0.36 per mile
- $233,000 using a Tesla model S, $0.58 per mile
- $150,000 using the ’59 Cadillac, $0.37 per mile
So, for its first life-span, driving the Cadillac comes out kind-of on par with the Nissan Altima. It’s higher in “acquisition” cost, and it makes its money back in cheap mechanical parts and cheap fuel.
That by itself is already a great thing. Then comes the kicker. All of that math assumes that after 6 years, the car is a complete write-off and I essentially dump it for scrap-metal prices (or $20 on CraigsList). And that assumption is where the Cadillac idea actually starts to make a little bit of sense.
A 1959 Cadillac 4-door with nice chrome, decent interior and good paint sells for $30,000, pretty much regardless of the mileage. It may need a couple thousand dollars to redo the front seat, but that is about it. So, after 6 years of driving, I could sell the car for its residual value. That means that for the Cadillac math I can take depreciation/the cost of the car itself out of the equation.
That drops the Cadillac’s $150,000 total-cost price-tag down to $120,000, and that in turn drops the cost per mile to something like $0.30. That’s 20% less than Altima cost, and pretty excellent. Or, I can keep the car and buy a second battery for (by then) $15,000 and go for a second 6-year 400,000-mile term. Adding the 2nd round drops the commute cost down to $0.19 or less per mile, which would just be down-right amazing.
All in all, by going for a classic car (i.e. a car that will depreciate / retain value based on its condition, not mileage) I can get to a much better financial deal than I can if I were to go with something current. The classic just needs to be up to the job of being a daily long-distance car in comfort, features, reliability etc (so a Karman-Ghia is out), and the Cadillac is a pretty good fit for that bill.
In all, at $110,000 going in, this for sure is not a cheap project. I get that. But, I think the numbers make sense across the 6-year 400,000-mile intervals. Plus I get to commute in style, especially compared to a high-mileage Altima (sorry Nissan :-).
Now all I have to do is make it work.
Disclaimers: I will update these numbers as the project moves on, just to see how it all turns out when compared to the early estimates. Maybe others can learn something from my choices. I appreciate that calculating cost-of-ownership over a 6-year period 400,000 mile interval is all just a bunch of estimating, assumptions, guesswork etc, and not at all an exact science. I do not want to tell anyone these estimates are somehow accurate, and encourage everyone to create their own model rather than follow mine. The (only) point here is that I used the same logic on all of the cars, the same assumptions on $$/gallon and $$/kWh went into each of them, and I think that makes the comparison valid enough.
####################### Update, at 3/4 of the way into a fully electrified chassis ##########################
The big-ticket drive-train items pretty much came in where expected. They’re purchased items, they come finished, so no real surprises. The cost (and the effort) of creating the battery containment, the wiring, the fuses, the hoses etc has been kind-of a nasty surprise and has added probably $3,500.
A second over-run is the PLC. All of the new functionality I’m looking to add to the car went way beyond what the original wiring harness could do, and introducing a PLC added $1,500. It’s sort-of outside the scope of the original project, then again that’s just selective accounting 🙂 and I’ll just add it.
All in all, the $12,500 estimate for the small-fry parts is trending closer to $17,500. Not horrible, but ouch.
Another big change is that I gave up on the original idea of building my own battery packs. It would have saved a LOT of space and would have made fitting everything so much easier, but it is simply too much manual labor. So, I traded the loose 18650-cells for used Tesla packs and had to re-visit a lot of the initial planning. That switch-out probably added $4,000, but I am keeping that one out of the cost comparisons because a) I can use the loose cells for a second project, and b) it shouldn’t happen to anyone else.
With all of those I’m still within the unforeseen part of the budget, but I can’t have many more of them….