Help This Autopian Reader Pick The Perfect Droptop EV-Conversion Car

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One thing in the tuning world I’m excited about in the coming years is more electric vehicle powertrain swaps. My take is that there’s a lot of exciting stuff there we’ve barely scratched the surface on yet. Plus, what if you have a cool old car that always had kind of a garbage engine, like my old BMW 325e? The low-revving inline-six was the least-good thing about that car. I would’ve dumped it for batteries and instant torque in a heartbeat.

Check out this video our friends at The Drive did some years ago if you don’t believe me:

Watch it smoke those tires! You had better believe my E30 didn’t do that shit.

Now, one Autopian reader named Jordan is thinking of doing something similar. Plus, he’s figured out a way to make Uncle Sam pay for at least some of it. Smart! Favorable tax incentives and loopholes are how you really get ahead in life, kids.

But Jordan needs our help to figure out what to EV-swap. He wants it to be a convertible because he has good taste, but from there he needs an assist from The Autopian Hive Mind:

I’m all-in on EVs and love the idea of converting a cool-looking older car to electric to have something fun and unique for short trips around town and just for fun. I feel like a 20-ish-year-old car that looked great but had lackluster power and/or a problematic engine could be a sweet spot to buy it for cheap and then bring out the best by ditching the ICE entirely.
 
I happen to live in Washington DC, where until 2026 there is a 50% tax credit for all costs associated with an EV conversion, which means I could afford a professional job. This is good because I know I don’t have the skills or time to do this myself. With less than 3 years left on the tax credit, I’d want to buy the car sometime in the next year, to give me plenty of time to figure out the rest. This means you all don’t need to find any cars actually for sale right now, but instead, identify the ideal model I should keep an eye out for.
 
He’s right that the District of Columbia does, in fact, offer some pretty serious tax incentives for an EV conversion. I think I’d probably triple-check with their Office of Tax and Revenue to be sure, but this initially sounds promising.
 
Now EV conversions are no amateur job. You’re dealing with cutting into the car to make space for a battery, which varies from vehicle to vehicle, and you’re working with potentially dangerously high voltage levels. I am not sure I would recommend this sort of thing to just anybody. Both David and Jason have superhuman levels of indestructibility at this point.
 
But we all have to start somewhere, and it’s best to start with choosing a donor car. Jordan continues:

My wish list includes, but is not strictly limited to:

  • Convertible–targa and t-top suggestions also encouraged!
  • 4 seater and booster-seat compatible to bring the whole family along
  • Looks cool
  • Good color (or boring color but cheap enough to add a wrap to the project)
  • Good candidate for EV conversion
  • In running condition (needs to be already registered in DC to qualify for tax credit)
  • Roughly late 1990s through early 2000s
  • Under $10k
I’m definitely biased toward European cars and so I’ve come close to pulling the trigger on a Saab 9-3 (in Gatorade yellow) or a nice, red BMW 325ci, but I’ve hesitated, not knowing if these would actually be a nightmare to try to convert. I’m slightly flexible on my list, but I’m pretty sold on a drop-top unless it is extremely cool or otherwise the perfect candidate for this sort of thing.
 
After I emailed with him a bit, he seemed a bit discouraged after looking at the costs involved. Here’s where we’re at:
Since I sent this out I’ve had a few other conversations. I’ve learned if I’m paying for a pro conversion, that’s really more like a $40k+ price tag, double what I had thought. So with the tax credit (which is capped at a $19k credit) it would be more of a $35k project on the low end, or a lot of DIY, which is just a much bigger project than I had in mind. Also I’ve learned pre-OBD II cars are much easier to convert–probably for the best I didn’t get that Saab! So unfortunately I’m a little doubtful if I can really pull this off, but I still love the idea and would be fascinated to read the suggestions and comments, or inspire another DC resident to take advantage of this tax incentive to do something cool!

This stuff isn’t cheap! Not yet, anyway. But I still want us to talk about it. I know that out in California, shops like EV West offer some amazing conversion kits and outfits like Zelectric specialize in certain cars—in their case, old air-cooled Volkswagens and Porsches. So it takes some doing, but it can be done.

I do see this sort of thing becoming more common as EVs do. After all, tons of Teslas get totaled out after just minor damage even though their batteries are still good. There’s about to be a bigger supply of these things soon enough. The bigger question will be how to do the conversions, on what cars, and both safely and cheaply.

We’re in the Wild West stages of EV conversions, so let’s help this young gunslinger pick his next electric steed. Share your thoughts with Jordan below—and expect more in the way of project car advice from us soon.

David Tracy’s Thoughts:

If I had to convert a car to an EV, there are two ways I’d go about it. (I’m going to ignore the convertible part here and keep it general). If I wanted a long-range cruiser, I’d look for:

  1. Space for batteries
  2. Body-on-frame construction (to make chassis modification easier)
  3. Reasonably small frontal area to keep vehicle demand energy down

I might go with something cushy on Ford’s Panther platform like a Grand Marquis wagon:

Screen Shot 2023 04 13 At 10.40.19 Am
Image: Mercurhy

It’s not too huge frontal area-wise, it’s body-on-frame (so you can add crossmembers/tabs for batteries and other EV components), and it got plenty of length to package everything. 

If I didn’t want a long-range cruiser, but just a commuter for ’round town activities, I might just snag something small. Maybe a VW Type III Squareback. It’s not body-on-frame, and it’s quite compact, but it should fit enough batteries in the cabin and engine bay get you at least 100 miles without breaking the bank.

Screen Shot 2023 04 13 At 10.45.07 Am
Image: VW

There are quite a few other great options for a ’round town commuter. Even an AMC Pacer wagon would get it done; maybe even a Corvair sedan? -DT]

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103 thoughts on “Help This Autopian Reader Pick The Perfect Droptop EV-Conversion Car

  1. I asked ChatGPT to give me a list of convertibles available in the US between 1990-1996 listed by Cd. It didn’t have access to Cd data but gave me some good ideas.

    Toyota Celica Convertible- has back seats, cool 90s styling and can be found for less than $10k. Decent space for batteries. Cd of .36 which was fine for the time. Some versions had OBD-II so care must be taken there. From a quick search it appears the 2.2L 5SFE engine used OBD-I. Downside is doing a RWD conversion might be hard without significant modifications.

    Any 3 series convertible from BMW is another good choice. I didn’t check the Cd but it is probably a bit higher. With RWD and a longitudinal engine, bolting right up to a manual transmission provides a simpler option.

  2. Chrysler Sebring. You can get one for $1800 and use all the money you saved on acquisition to make it the best (and probably only) one around.

  3. Triumph Spitfire.

    mechanically dirt simple, already IRS, clamshell hood so engine bay access is amazing, the whole car weighs about 8 lbs and only had 45 HP to begin with..

    pull the motor, trans and driveshaft, mate a Leaf motor to the rear diff and put the battery pack where the motor & trans were.

    even with the smallest Leaf motor, it will go like a raped ape and handle very well.

    1. A couple years ago I read about a battery-swapped TR3 that I still think about all the time (that was my mom’s first car, so it looms large in family lore). Spitfire’s probably a little more practical, though.

      But oh no, what if you can’t reuse the Lucas bits!?

    2. When I saw the lead image with the graphic overlay, I immediately thought, why would you put the motor in the front? Just put it at the rear axle and ditch the weight of the driveshaft.

    3. Yes, an already sketchy handling car with swing axle IRS definitely needs to have a magnitude more horsepower and it’s chassis groaning under extra weight…..

      Richard Porter said he tried one and it was basically undrivable.

      1. nissan leaf battery pack weighs about 700 lbs. a fully configured Spitfire engine bay with all the usual accessories (block and trans, battery, radiator, fluids, intake and exhaust yadda yadda) weighs about 450.

        dropping in the Leaf motor adds about 100 -150 lbs at the back.

        upgrade the springs and shocks and you should have one hell of a fun car.

        1. Spitfire all the way (come on, who needs a back seat?). I have a ‘75 Spitfire sans drivetrain waiting in my driveway for space in the garage (anyone want a ‘55 tbird?). The plan is to use the batteries from a Nissan Leaf and an 80hp AC motor connected directly to the diff, so no drive shaft. Manual brakes and manual steering so no need for vacuum. So anxious to get started.

  4. I’m thinking a big old 1960’s 0r ’70’s full size Chrysler Corp. convertible, expensive, but cheaper than a GM or Ford offering of the vintage.
    Full frame, plenty of space and cool for cruising to the Love Shack with your friends.
    Might even be able to do the Jeep thing and just substitute the drive train.

  5. How about a Porsche 944? Technically a 4-seater though probably only kids in the back, convertible if you want, fun colors sometimes, not too hard to find well under $10k if you’re patient.

  6. Type III is a neat idea with existing conversion kits, but I’m thinking either:

    1. Fox-body Mustang with stickshift and I4 or V6 engine – nobody’s gonna cry when you chuck the engine, and bolting a motor to the trans is the easiest kind of swap.
    2. Something front-wheel drive like a SAAB, swap in a whole LEAF powertrain and battery.
  7. First off, hello fellow DC Autopian! There are a few of us in the area. Maybe we can do a meet up sometime.

    When it comes to the question I’m a little bummed that 4 seats are a requirement because I feel like a cheap mid engined car is a good answer to this question. The electric motor and a lot of components would sit over the rear wheels which will be good for the driving dynamics. I think an early 2000s MR2 could be fun and a buddy of mine is toying with the idea of doing a Porsche 914…which also seems like an ideal candidate for this. Or a Boxster that’s been absolutely thrashed…the IMS bearing can’t grenade itself when there is no IMS bearing!

    For more reasonable choices that actually fit your criteria 2000s VAG seems like a good way to go because of how unreliable their ICE engines were and still are. No one is going to mourn about an old 4 popper out of a Golf Cabrio or an A4/A5 convertible from that time biting the dust. Hell if you like the styling there are still New Beatle convertibles from that era kicking around and the base engines on those were notoriously underpowered. IIRC the first batch of them were hitting 60 in around 12 seconds when all the magazines got a hold of them for testing.

    You could also just go pony car. Early S197 Mustangs are starting to get really cheap and I honestly think they look fine styling wise. Even the V8 from that era is nothing to write home about and they should have enough space for you and the kiddos to drive the car out to dinner or a soccer game on the weekends. You can even paint it grabber blue which is one of the best colors in the entire industry.

  8. My first answer was a Miata, then a Prowler, but a spot for car seats blew those two ideas right out of the water.
    Sounds like some sort of bigger sports car would work better: one of the last Firebirds with the 3800?
    Maybe a TJ, one of the ones with the Chrysler 2.4 and not the AMC 2.5?

  9. Can anyone point me to an article or something that spells out how an electric motor is programmed? Preferable in language a non-electrical engineer can understand. I would assume you need to match the throttle to the weight and stuff and it would not be straightforward.

    1. You need a motor controller. A motor controller takes power in from the battery pack and controls how that power is sent to the motor. The gas pedal is connected to a sensor that sends a signal to the motor controller. That signal can simply be a variable resistor (like the volume control on an old-school radio).

      Some sketchy EV conversions use the throttle body from an ICE car. It has return springs, it usually doesn’t stick, you can reuse the throttle cable to connect it to the pedal – all great shortcuts. The physical throttle body is useless, but you can wire the throttle position sensor into the motor controller. The throttle position sensor becomes your speed control.

      The motor controller also controls regenerative braking.

      When building an electric car, you have to pick a battery pack, motor, and motor controller that all work together. For example, if you have a 400v DC battery pack and an 800v AC motor, then you need a motor controller that supports those two things. If you want regenerative braking, you need a motor controller that supports it. This is a lot like selecting parts when building a computer. They all have to be rated to work together.

      Actually programming the motor controller is a lot of “it depends”. Some brands of motor controllers have proprietary programmer units that look a lot like OBDII scanners. Those suck because you have to buy, borrow, or steal a programmer that you’re probably only going to use a couple of times. Each motor controller just has a set of parameters that you are able to control. Those parameters are stuff like regen strength, acceleration ramp-up time, etc. Acceleration ramp-up time is interesting. Since electric motors have all their torque available from a stop, you don’t want to suddenly go from stopped to full power. That suddenly slams gear teeth together inside your gearbox and breaks things. So you give it a 1/2 second to 3 second delay. If someone suddenly floors the accelerator, then it ramps up power over the course of a half second or so.

      I don’t know if this is helpful. I thought since I only half understand this, I might be able to explain it.

    1. I second this idea. Chevy made a bazillion of them – https://en.wikipedia.org/wiki/Chevrolet_Camaro#Sales . Aftermarket pieces for upgrading suspension, brakes etc. are readily available. Variations included convertibles and 4-5 speed manuals, though I don’t know how many were sold as drop-tops and manuals.
      Find yourself a CA/AZ/NV car with a crap engine.
      BTW the 4th gen convertible – https://en.wikipedia.org/wiki/Chevrolet_Camaro_(fourth_generation) – isn’t bad looking. I don’t know if it was ever sold with the 6 speed manual.

  10. I struggle with the late 90’s part of the problem, but what about a 996 cabrio with a blown IMS? It’s a really tight rear seat, so you might have to check if the booster fits, and it may not be as stylish as earlier or later 911s, but it’s still an amazing-handling car and the packaging would be really convenient for a battery conversion, specially if you got a Carrera 4 (widebody, big transmission tunnel where you can put a nice long battery pack). A C4 cabrio automatic would be really cheap because everyone wants hardtop C2 manuals, throw in a blown engine and you have a hell of a deal.

    Besides that, I can’t think of much, I tend to avoid 4-seat convertibles as a matter of course. Maybe a Golf or Cooper cabrio? If I was doing an electric conversion I’d do a Karmann Ghia or a Cadillac Allante, both were beautiful cars with less exciting drivetrains, but neither matches the requested categories.

    1. You can fit small car seats in the back of a 996 if your front passengers aren’t super tall. I would not do it in a coupe, but with a cabrio you can just lift them in, so it ends up working OK.

    2. Just wanted to add that if there are legal requirements for previous state as another commenter mentioned, you can get a running C4 cabrio automatic for 11,000 and sell the engine for close to 8,000, there are lots of people looking for these engines for their blown up 911 or to swap into their Boxster. I’d make it RWD, so you can put batteries where the trans and diff used to be. The rear-engined layout would make fitting something like a Tesla drive unit an absolute peach, and even leave room around it for a secondary battery pack so you don’t throw off the weight balance too much.

  11. Off the top of my head, I would guess that the more primitive the electrical system in the donor car, the easier the conversion would be. You just need a way to supply 12 volts to the systems that run off it, and the new power electrical system can be essentially stand-alone.

    That means old, older than 1990s/2000s. And something with a crap engine, as Patrick said. Malaise-era cars are crying out for EV conversions, but convertibles were scarce and build quality was generally awful (except Mercedes-Benz).

    Here are a few vehicles that come to mind, not convertibles, but all available with T-tops or big-ass sunroofs:
    Camaro/Firebird
    Porsche 924 (rear transaxle might make it easier too)
    Early Fox-body Mustang (with the boat-anchor six)
    Volvo 140/240 (though some purists might hate it)

    A C3 or C4 Corvette would be a fun one too, but only two seats…

    1. Two extremes: Either go pre-OBDII to get as few electronics as possible, or go new enough to have as many electric accessories as possible. IMO the 1990’s – 2000’s time range OP gave makes this more difficult than it needs to be.

      For an older car, try to keep the AC, power steering pump, and (if you’re trying to save every dollar) alternator. Find a way to mount them and add a small electric motor to drive that mess separately from your actual drive motor. It’s not the most efficient route to take and it requires a little fabrication to mount the accessories, but it is fairly inexpensive.

      For a newer car, look for something with as few belt-driven accessories as possible. Buy an electric AC compressor that can run off your main battery pack. Use a DC/DC converter to convert from your main battery pack to 12V, and use that to power the other accessories and electronics.

  12. Edit (thank the great Autopian in the sky that we can do this now): I see I missed a requirement, which renders my whole argument moot. I still think this would be interesting to see though.

    I’m probably going to get a lot of hate for this, but:

    Cool older drop-top with lackluster power? Miata is always the answer. It would also be interesting to do a before and after comparison to see how adding a bunch of weight (hopefully down low) and power to a Miata would affect it’s fun factor.

  13. Land Rover Defender. They’re not known for their speed, body on frame so you can cram it full of batteries, and the engine is decidedly not part of the appeal of these cars.
    Plus they’re put together like a giant Meccano set, and the controllable nature of the low end torque will make a brilliant off roader better.
    This line of reasoning also works for a Wrangler.

    1. If I were going the British route, I would pick the Jag XJS convertible. There’s plenty with non-functional V12’s out there. Plus, you’re going to be removing all of the electronics so it would likely be much more reliable.

      1. I will personally dig up the corpse of Sir William Lyons and use it haunt you and make your night time a living hell if you attempt such blasphemy.

  14. Came to comment, “please don’t ruin another Spitfire.” Thankfully the criteria place one firmly out of the running. My suggestion: mercury Capri! Cheap, fun, 4 seats, plentiful parts following. Just don’t ruin an xr2, send that my way.

  15. If you’re swaping it for an EV power train, why does it need to be a driver? Get a non-running (blown engine) BMW 3 series on the cheap, and convert it

      1. registered and running or just registered? I mean if it’s a DYI, it’ll probably not be running and completed by time the next registration date rolls around

        1. DC requires inspections before the DMV will register a vehicle. This is a hard challenge. The vehicle not only has to be running, but needs to have all the emissions stuff functioning properly.

          1. So what happens to a DYI project that takes more than a year? You can’t find an already registered car, that’s now undrivable and covert it? You can show the DMV it was registered when you started the EV swap

          2. As a DC resident this is such a perfect example of our local government: great idea and stupid execution. It’s wasteful to need a fully functional car that passes emissions regulations before removing those components to make it more environmentally friendly with an EV conversion. A more environmentally sound way would be to offer registration after the conversion of a vehicle that can’t pass emissions, but is otherwise in good working order.

  16. Any generation Chrysler LeBaron convertible. Bonus points if it once belonged to John Voight. This would actually make a pretty awesome q-ship. No one expects old LeBarons to be capable of getting out of their own way, much less capable of leaving a ‘Stang at the stoplight.

    In any case, I’d suggest just about any FWD ragtop for an EV conversion. They are generally cheap and plentiful, and EV conversion is the easiest way to get the proper wheels driven.

  17. Hmm. Interesting idea and the requirements list knocks Miata off the list.

    My first thought as Monte Carlo with T-tops. Not the SS with it out of your price range, but the regular model.

    Sure it is a two door, but easy to get in an out of the back, the seats can take a car seat or be modified to do so.

    I also expect you will need to do some body and other work along with this, still seems like a good fit.

  18. 4 seats an a convertible? Way to make it tough!

    I’m assuming that you don’t need new(er), so let’s go back. Back to a day when white suits were in, and bull horns were strapped to grills…

    Yes, let’s go to 1979, with the big caddy convertibles. Full frame? Yes. Huge engine bay, with a stock 500ci engine? Yup, more room for a motor AND massive battery space. That baby got back too, so more battery in the trunk or storage. This Era was fwd too, so no driveshaft, rear-end, or floor humps. Parts are available. Just don’t go calling everyone a dipstick.

    1. Yeah that is tough. I hate, like really hate suggesting, but a convertible PT Cruiser fits that profile, and will not break the bank. But I wouldn’t want to drive it.

      A much better option might be a Mustang from that era.

      For real fun, it would be great to find a blown Mercedes SL from that time.

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