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Discussion Starter #1
Hi Everybody

Ive been reading posts on this forum for a while and finally thought I'd start my own topic.

I want to build an ev to drive to work (about 100km round trip) and also to have a bit of weekend fun in, maybe even eventually join a car club.

Until now Ive been into big v8 cars (3500lb plus) but because of my larger range requirements Im thinking of going for a small car, 4 seater, probably a ford lol like an anglia, escort or capri but I might also look at a starlet, corolla or mazda as often there cheaper and easier to find. I dont need sonething with insane performance but I do want to try and keep cornering performance if I can.

While it might seem strange to start a post without having a car to convert yet Im trying to do as much learning as I can 1st. I know Im going to go low tech with a 9 inch D.C. motor (forklift), keep a manual transmission and probably run a 144v system.

I have a couple of questions about batteries. How do i calculate sag so I don't drop under 144v under acceleration?

Also battery placement. Because I don't want to ruin handling and Im looking at a small car so battery placement may be tight. Ive been thinking about whether it would be possible to use narrow batteries and sit them on the floor and then build a false floor above them. Has anyone attempted this or is there some huge issue I haven't accounted for?

Thanks in advance
Brennan
 

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Actually, it's a good idea to research and plan what car you would convert before buying one.

Not sure what vehicles are available where you live, but around me people prefer to convert light duty (formerly 4 cylinder) pickup trucks. Typically we can find one fairly cheap, and because it is a truck it is designed to handle higher loads. This can be important because depending upon which batteries you choose, your conversion can end up heavier than the original ICE version was. No matter what vehicle you pick, calculate the weight of your new components and compare that to the load rating of your candidate vehicle. You might have to swap in heavier springs and reinforce places like spring mounts and shock absorber mounts, as well as install stronger brakes and tires with more belts.

We try to place batteries low in the vehicle - typically just above the frame rails. That helps the vehicle handle better, although if it ends up heavier than it originally was then expect it to handle somewhat sluggishly. The pickup truck layout allows us to place the batteries under the pickup bed (many times we don't reinstall the original bed, but build a simple platform over the batteries). In cars we haven't tried a false floor but instead took out the rear seat and placed the batteries there. Build a sturdy battery box / firewall to protect passengers from a battery mishap.

Not sure about your concern about battery sag during acceleration. As you use up your charge your pack voltage will go down somewhat, but how much depends upon how far you've already driven as well as the type of batteries you choose. Terrain you drive over, as well as other loads (such as lights on or heater on, etc.) also effect this. I think there are already good articles on sizing batteries so I encourage you to find and digest them.
 

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I'm by no means an expert, and have yet to complete a conversion, but my research led me in a different direction. Some thoughts (that anyone should feel free to correct):

1) Range depends heavily on the batteries. The weight of the vehicle, less so (depending on average speed and how much stop/go is involved). For range, it would be better to have a heavy car that can fit more batteries than a light one that can't, with the understanding that more batteries come with more cost, of course...

2) For 100km, you're looking at a battery pack somewhere along the lines of maybe 16-24kW, which to me implies sourcing them from a factory EV like a Leaf or Volt or whatever is common in your area and a few years old. Cheapest way in is to buy a whole car, preferably one that has lots of body damage, take what you can use and sell the rest...if you've got the space/time.

3) There's nothing wrong with something like a DC9, but (again, depending on availability), there's a pretty good chance it will be similar money to get something more powerful pulled out of a factory EV these days. Controlling is tricky, but the Leaf motor at least has a pretty full-featured controller from Thunderstruck, and can be separated easily from its gearbox for easier mating to the ICE car's manual transmission.

My big advice is this: Pick a car that you will love to have when complete. With the amount of time you will put into this conversion, the cost of the chassis and parts can quickly become eclipsed.

Where are you? What's your budget?
 

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Discussion Starter #4
Hi Paul and Tremulene



Thanks for your replies and suggestions.


@ Paul, I was always going to upgrade brakes and suspension parts for handling but I will make sure I factor in weight increases as well. I understand your thoughts on having a larger car to give you more potential storage space but surely ot takes more energy to move a bigger car. Sounds like a vicious circle.

@ Trem. I live in the southern part of New Zealand. I'd love to source some Volt batteries as they seem very good bang for buck. Unfortunately I dont think they were released in NZ so getting some bought in from USA might be a path I look into. We have alot of Nissan leafs here but Im a bit nervous about them. I was under the impression maybe there batteries didn't last. I think your right about a 24kwh system is where I need to aim for.

Thanks again for your help

Brennan
 

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You could start by just buying a Leaf and driving around in it while you research and source parts for your project car. This will give you some idea of what a certain level of EV performance is like. And if someone crashes into your Leaf in the next year or two, you have the perfect parts car ;-)
 
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