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. It’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.
400,000 miles means the moving parts have all been replaced at least twice, and at 6 years (and this many hours) the insides are pretty much done too. To make a car go beyond that would mean a complete rebuild / restoration, so (for me) that is a reasonable cap as the useful life of any regular bought-at-the-dealer car. It all 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 Nissan Altima that I’d buy at $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, 40k miles for a set of tires, 100k miles for shock absorbers, etc etc) 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, purchase price $110k all-in. The biggest factor here is that no-one at the dealership would even venture a guess on 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 happens once, say around 250k. With that assumption, and adding in the maintenance, tires, repairs, wear&tear parts, the electrical bills etc, the end-number comes out to $0.57 per mile. That’s 1.5 times what the Altima would cost, and that does not sound unreasonable. When you look at the price-delta between the Tesla ($110k) and the Altima ($20k) ist’s actually pretty good.
That’s what started me down the path of building my own EV. If the most professional, solid EV can’t even come close to an Altima, how are the lighter ones going to stack up? Most don’t have the range, the life-span is a complete unknown, and $0.36 is surprisingly hard to beat.
The math on the Cadillac is 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 breaks, a regular project car. To restore that into something shiny takes maybe $22,000. There’s no engine/transmission work, the interior is around $5k, the chrome is another $5k, powder-coating the frame is $1,500, $2,500 in brakes and suspension parts, $750 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. So, cost of the base car is around $30,000.
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. 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.
##################################################################################### Update, at 3/4 of the way into a fully electrified chassis (summer 2020): ##################################################################################### 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 etc has been kind-of a nasty surprise and has added probably $3,000-$4,000. All of the new functionality of the car went way beyond the original wiring harness, so I am adding a PLC / control-computer to make things better, and that added $1,500. All in all the $12,500 estimate for the small-fry parts is trending closer to $17,500. Not horrible, but ouch.
The other big change is that I gave up on building my own battery packs. It would have saved a LOT of space and made fitting everything so much easier, but it is simply too much manual labor. So, I’ve traded the 18650-cells for used Tesla packs and had to re-do a lot of thinking. That shuffle has cost probably $4,000, but I’m keeping it out of the cost comparison because it shouldn’t happen to anyone else. I’m still within the unforeseen part of the budget, but can’t have many more of them…. #####################################################################################
From there I add in the maintenance, the tires, the repairs, all per the same logic as the other 2 cars, and I can compare the end result. To drive 400,000 miles, it costs:
- $145,000 using a Nissan Altima
- $233,000 using a Tesla model S
- $150,000 using the 1959 Cadillac
So, for its first life-span, driving the Cadillac comes out kind-of on par with the Nissan Altima. It’s higher in purchase cost, and it makes its money back in cheap mechanical parts (chrome is expensive) and cheap fuel. That alone is a great thing.
The kicker comes at the end of life-span #1. A 2012 Nissan with 400,000 miles on it sells for at best $20 on CraigsList in 2018. It is a complete write-off. A 1959 Cadillac 4-door with nice chrome and good paint sells for $30,000, pretty much no matter the mileage. It may need a few thousand dollars to redo the front seat, but that is about it.
So, I can sell the car for its residual value, and take that out of the cost for 6 years of driving. That now goes from $150,000 to $120,000, which makes the cost per mile something like $0.23. That’s already excellent. Or, I can keep the car and buy a second battery for (by then) $15,000 and go for the 2nd 6-year 400,000-mile life-span. That 2nd round drops the commute cost down to $0.12 or less, which would be down-right amazing.
In all, at $150,000 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 used 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 compared to 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 a lot 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.