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Discussion Starter #1 (Edited)
Hey guys figured I'd make an account here even though I'm still firmly at the planning phase of possibly making an EV but this seems like a good place to source info!

A bit of me: Homeland Finland, trucker by trade, garage gearhead by nature. As a hobby I mostly do homebrewing and build streetfighter motorbikes but ATM looking to get into building a daily runabout EV to replace my current gas guzzler Volvo Xc70. As a platform I've been thinking about a mid nineties Renault Megane Coupe Cabriolet. Why? Because I want a droptop car, compared to others those are cheap as chips here, and they usually don't have much over 200tkm on the clock, or driven in the winter much which is a good thing since mid nineties cars have a strong tendency to be pretty rotten due to the long autumn and road salting in the winter.

I'm not entirely new to electricity after spending three years in school studying to be an electronics guy but even though I did graduate something like fifteen years ago I've never worked one day as such but I reckon if I scratch my head hard enough I can still probly bring back some small fragments.

There are some fundamental questions I'm currently trying to search answers to like how do you heat an EV in the winter. I've understood there are some electrical heating elements you can install to replace the original unit but wouldn't that eat your range even more since it's cold already so been trying to find if it's a common practice to fit a diesel heater into an EV. now I know it would create some emissions but I don't want to freeze my bum in -20c, besides it'd be a great way to get the car warm beforehand via a gsm relay. It could also be used to preheat the battery compartments to get more power out of them during the cold months.

Second questions is how retarded of an idea would it be in general to convert a convertible in the sense that how big of an impact would it have to my range to drop the top? Cabrio Meganes usually have AC too but I'm a bit on the fence about whether or not to keep it. But since they convert pickups too I don't suppose wind resistance would be that big of an issue.

Third: anyone ever made a sheet metal box to replace the fuel tank and put at least some of the batteries there? Cabriolet cars usually have just a teeny tiny boot because of the roof cavity so not a whole lot of cargo space to begin with.

Fourth is the obvious what voltage and how much of a budget do I need? Looking to get about 100km per charge, top speed 120-140km/h, usual cruise speed 80km/h with a few km:s of 100, two fairly steep albeit not that big hills on my way to work, almost always travelling alone, usually driving about 30-40km at once. I found some formulas to start decyphering that already but educated guesses welcome.
 

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... how do you heat an EV in the winter. I've understood there are some electrical heating elements you can install to replace the original unit but wouldn't that eat your range even more since it's cold already...
An engine produces waste heat, and that's what heats the interior. An electric motor and controller (and even the battery to some extent) also produce waste heat, but not much. As a result, yes, heating will eat your range.

Yes, you're using up battery when the battery is at its least effective.

... been trying to find if it's a common practice to fit a diesel heater into an EV. now I know it would create some emissions but I don't want to freeze my bum in -20c, besides it'd be a great way to get the car warm beforehand via a gsm relay.
A seat heater can be a more effective way to handle this than an air heater, although at -20C you would still want some air heating, of course.

For pre-heating, why not use the AC power that you're plugged into anyway? If you're pre-heating when parked away from home and without a plug-in, the location had better be very close to home... given the range which will result.

I think as soon as you fire up a diesel heater, you might as well be driving a hybrid, and getting actual propulsion out of the fuel and heating with the waste heat, rather than getting just heat. This is one reason that battery-electric vehicles are nearly non-existent in most of Canada.
 

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Second questions is how retarded of an idea would it be in general to convert a convertible in the sense that how big of an impact would it have to my range to drop the top? Cabrio Meganes usually have AC too but I'm a bit on the fence about whether or not to keep it. But since they convert pickups too I don't suppose wind resistance would be that big of an issue.
There is a drag cost to the drop top, but that shouldn't be as bad as a pickup truck. Keep in mind that pickups can carry lots of battery, so a pickup conversion with decent range does not imply that drag is not an issue with this body shape.

I think the early popularity of pickup conversions (such as Solectria's S-10 and the Ford Ranger EV) was due to a combination of ability to carry batteries, and the desire for a functional vehicle for commercial and institutional users, rather than pickups being any good as EVs.
 

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Third: anyone ever made a sheet metal box to replace the fuel tank and put at least some of the batteries there? Cabriolet cars usually have just a teeny tiny boot because of the roof cavity so not a whole lot of cargo space to begin with.
I haven't done it (or any conversion), but I have seen others take this approach. I would expect a front-wheel-drive modern car such as the Renault Mégane to have a fuel tank located under the rear seat, fitted around the rear suspension. A quick web search suggests that this is true for the Mégane, and it looks like it might be a really convoluted shape so a matching box would have very little usable battery space.


I assume that the Mégane has a rear seat, even in the cabriolet. If the above image of the tank is correct, my guess is that it is as seen from above and ahead of the tank, so the shape of the top shows the shape of the floor, which in turn is shaped to the seat cushion. If you are willing to sacrifice the rear seat, replacing it with just a raised area for cargo, perhaps the floor could be cut out in that area and replaced with a more useful battery box? You would need to careful to maintain structural integrity, of course.

In a few minutes of web searching I couldn't find a reasonable image of the underside of a Mégane, or the rear suspension area. Although common in Europe, I suppose this vehicle is obscure by international automotive standards - it was never sold in North America, for instance. If you have a good image of the chassis layout, it would help to share it. Although it is only external views, I did find a technical drawing which might help lay things out.
 

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Discussion Starter #5 (Edited)
Alright thanks for the info so far guys, really helps me getting started on the planning!

I knew the Megane fuel tank is a bit oddly shaped but didn't realise it's THAT bad. One option would be to chuck the spare tire and put the box under the boot, pretty much all french cars have a flat boot bottom underneath for the spare to hang off a wire rack. Well at least older ones. Definitely no modifying the frame in any way, the rules are VERY, VERY STRICT here. The conversion can be done, but certain loopholes have to be used to circumvent things, like the car cannot be newer than 2001 because of the EU regulations, absolutely no homemade electrics, everything has to be E-marked, documented, all electric connections have to be inspected by a professional inspector etc. Wierdly enough things like ABS CAN be removed IF there is a parallel model that hasn'g got them.

I know heating with diesel would be a bit counter intuitive but pretty much a necessity at these winter temps. Looking at for sale ads of used nissan leafs here, every single one has a webasto. I do have the opportunity to charge the car in both ends as I have a "pole" on my truck parking space with a 16a fuse so I most porbly will be heating the car from the mains, if only the fuse can take the charger AND the heater. One idea that came into my mind was to fit a tank of say, ten liters, under the hood, fill it with coolant, heat it up from the mains and run it through the original element with a small pump. I suppose it should be able to hold heat enough for the half hour trip, though it'd rack up the electricity bill quite a bit. Haven't decided on that yet.

I might have to ditch the convertible idea for cost effectiveness, been perusing the local craigslist (nettiauto) and rag top meganes start at 2k, whereas hardtops can be bought for mere hudreds, even under but those usually have stood for a while, have mold in the interiors and the anti-theft system is locked. One option I had in mind was an A-class merc. They occasionally pop up for sale with engine troubles and asking just hundreds. Whatever the car is it will have to be compact since I cannot fit a full sized sedan into my garage. Oh and it has to be an interesting car in some way, I'm too much of a petrolhead to be driving some dreary box like the geo metro this Ben Nelson guy has done in youtube, or if I've understood right, as it is sold here, Suzuki Swift. And I need four seats because two kids with safety seats. If absolutely necessary the boot can be sacrificed, seats cannot.

Anyhoo just tossing ideas at this point but good to get feedback as I'm only scratching the surface of all of this, and my EV bank balance ATM is showing about a hundred euros so not a whole lot apart of keen studying will be happening anytime soon!
 

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Discussion Starter #6 (Edited)
Come to think of it, the W168 M-B A clas will make a perfect EV for my needs. Hate the interior but like the looks, it's a five seater and the cheapest ones with engine troubles go for 500, sometimes even less than that.

EDIT: scratch that, the engine bay is super cramped and the gearbox is partly crammed under the cockpit, and the whole car has more electric gizmos with three letter abbreviations than what you find in an STD clinic.

Next up: Opel Agila(Suzuki WagonR+)
 

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...Definitely no modifying the frame in any way, the rules are VERY, VERY STRICT here.
If modifying the floor of the unibody structure will been seen as structural modification which is disallowed, then most cars will be problematic. Perhaps a hatchback with a flat battery pack as a raised floor of the whole cargo area? Of course that would exclude cabriolets.

Come to think of it, the W168 M-B A clas will make a perfect EV for my needs. Hate the interior but like the looks, it's a five seater and the cheapest ones with engine troubles go for 500, sometimes even less than that.

EDIT: scratch that, the engine bay is super cramped and the gearbox is partly crammed under the cockpit, and the whole car has more electric gizmos with three letter abbreviations than what you find in an STD clinic.

Next up: Opel Agila(Suzuki WagonR+)
These are examples of cars which might work with a flat battery pack in the cargo area (and maybe down into the space vacated by a removed rear seat... which you won't do if you want five seats (but would the cabrio be a five-seater?).

The cramped engine compartment of the A-Class might be manageable if you don't try to jam any of the battery into it. All the superfluous M-B complication might be more of an issue...

For anyone not familiar with this design (which I think is an impressive packaging job), here's the W168 engine and transaxle... it's sloped like that to follow the sloped footwell floor:

The photo is from the right-hand side, and you can just see the right-side output of the differential under the front of the engine. This is the transmission by itself (also from the right-hand side); you can see the bellhousing (where the engine would attach, and where you can mount an electric motor), which is behind the axle line and jammed right against the floor:
 

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Discussion Starter #8 (Edited)
Yea been doing a LOT of calculations and it seems this just isn`t gonna happen. I`m looking at north of eight grand, PLUS whatever car I want to convert and I just don`t have that money.

Fear not, for all is not lost. I have decided to make an EV, and that means an EV I will make. Though it seems the outcome will, instead of four, have two wheels as per my original plan years ago. I`m still most probly gonna get rid of the Volvo once I get it paid and get something more economic instead, if possible an Opel Ampera, but the build I will be converting will more than likely be more into my core area of expertise. Alas I fear nothing at all apart from studying will happen for a good while still, but the outcome should cost less than half of the car, and be easier to slip past the cracks of the law.

BTW that MB engine is pretty genius, it`s shaped like that so it would slide UNDER the car rather than INTO it in case of a head-on collision. The cheapest ones cost about a grand here so might consider getting one and keeping it as is.
 

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I realize that the car conversion idea is off, and a motorcycle doesn't have a heater, but just to follow up...
...
I know heating with diesel would be a bit counter intuitive but pretty much a necessity at these winter temps. Looking at for sale ads of used nissan leafs here, every single one has a webasto.
It's hard to imagine that the winter weather there is more severe than here in Alberta, Canada. While there are not many Leafs, they are still the most common battery-electric car here. Diesel is readily available (it's used by almost all larger pickup trucks and of course essentially all larger trucks and buses). Still, I've never heard of anyone adding a diesel heater to a Leaf here (and I haven't seen such a heater mentioned in a for-sale ad)... which doesn't mean that it hasn't been done, of course! Maybe they all have them and they don't want to talk about it...

Now that I think about it, the idiots who have decided to run battery-electric buses in Edmonton plan to use diesel-fired heaters in them... and heat is needed for more than half of the year here. Why not just use hybrids (which are cheaper than battery-electric and are proven to be reliable and effective) and use the waste heat from the engine?

Reading more about this, it appears that even some production EV manufacturers have offered optional fuel-burning heaters; the Volvo C30 EV was mentioned as one, but I don't know if this is true.

If anyone is considering stored heat, I suggest looking into eutectic materials.
 
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