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Discussion Starter #1
Your skill level with auto mechanics and fabrication : no hands on experience with cars but I know the basics (and a bit more)

The range you are hoping to get (how many miles/charge) : not a problem in my use case, i'll be happy if it goes more than 10

What level of performance you are hoping to get : while it would be nice to go around 40mph, it probably wont happen

How much money you are willing to put into your project : $5000

This car is going to be an engineering project I'm going to be working on and something to put on my college admissions papers. While it might be a throwaway project now, I would like to eventually make this into a usable car in the future. I've read through most of the EV wiki topics but I'm still pretty stumped on the wiring situations. Since I have no budget, my plan was to create a basic 72v DC system using lead acid batteries but besides that, I'm not sure what parts to use in order to keep the build under budget.

Questions :
- Where would one go to buy budget forklift motors?
- Alternatively, what is a good off the shelf 72v motor?
- What are the max continuous current and and max pulse current of standard lead acid car batteries?
- Is buying a cheap controller worth it? Whats the difference between an Alltrax and Curtis? For someone little soldering experience, is building an DIY controller safe?
- with this setup, would it be better to go clutchless?

Thanks in advance for the feedback
 

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Having owned CRXs and Civics, I would not want to use a CRX for a conversion due to the lack of battery space. A Civic hatch - with the rear seat eliminated to provide a good battery space - would be both less expensive to buy and more practical to build.

Best wishes in your project.
 

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Discussion Starter #3
I forgot to mention, would it be cheaper to buy an off the shelf adapter plate for the transmission or would it be cheaper to find a preexisting adapter plate model and get it made at a CNC shop?
 

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If I'm following you right... you what the cheapest possible build, don't actually care much about the project, it's something to set you apart from other candidates and something fun to work on.

You can go super, super cheap on this.

Where to find a forklift motor? Show up in person at any forklift repair place, the less corporate the better. The conversation goes like this: "Hi, I have a weird question. I'm a high school student building a summer project. I would like to use an old forklift motor to power a car. I have my own tools, do you have any junk forklifts that I could take the motor from before you throw it away?" Small businesses are hoarders. I get mine for free, at most they're worth ~$200 in scrap. Email probably won't work.

A Prius inverter ($150-300) will suffice as a DC motor drive, which might be your cheapest option. You'll need some control circuitry from the Open Inverter forums. I don't know if it's popular enough yet that anyone's selling any board for it, but it's been tested.

You can make your own adapter plate with very simple wood cutting tools on aluminum and a runout indicator.


But speaking of Prius...

Alternatively, buy a 2nd or 3rd gen Prius transaxle for ~$150-$300. No engine, just the transaxle.

While there, buy the inverter ($150-300), and cables. And the HV contactor out of the battery. And the gas pedal. Maybe the brake pedal. And the coolant pump.

They don't have to match, you can power a 2nd gen from a 3rd gen and vise versa.

Both of these have workable control boards available from EVBMW.com's webshop, using the Open Inverter hardware. Check them out on the Open Inverter forums. You'll probably spend another hundred or two on that.

So, you can get an AC motor drive, transmission, axles, speed controller, DC-DC step down 12v converter, boost converter for higher speed, and control board for under $1000. Under $500 if you're lucky. Soon, for Gen 3 Prius's, battery charging will be enabled so you won't even need a charger. Replace the whole driveline of your vehicle. Then it's mostly a challenge to fit the axles and such.

For batteries... go to several general automotive places in your area, wherever people typically replace car batteries (oil change places, not "real" mechanic shops), and ask them if, there are batteries that are just weak, but not broken (low cranking amps on their load tester, usually how they talk people into replacing their battery before one of the cells outright dies), if you can buy those back for the core charge (mandetory recycling deposit, $10), or if you could leave a deposit for them to set some aside for you. Start doing this now, in case they have to set them aside for you before they enter the system.

Starter batteries are completely the wrong choice for an EV. Even deep cycle lead acid batteries are the wrong choice. But the cheapest way for you to get 72v, with enough amps to move a vehicle, is $60 on core charges for 6 old starter batteries.

They might only last you 10 deep cycles before their range drops off, but it's enough to be proof of concept, and might last you a month of really short range driving. And when you're done with them, it's hard for an individual to get a core charge directly, without buying a new battery in its place. So you'll probably have to scrap them. The last time I took batteries to a specialty metals scrapyard I got almost $10 apiece for them so, you're almost just renting them for free.

...

Your car will use ~6000 watts to go 40mph.

You'll use ~140 watt-hours per mile at that speed. So, if you only want 10 miles range, 1400 watt-hours.

A car battery is 12v and ~50 amp hours, so, ~600 watt-hours for a smaller one. If you're using 6 you've already got 3600 watt-hours, which means your 10 mile range will only deplete the batteries to 62%. Your batteries might survive more than a few trips.

More batteries is better, if you can carry 12, then carry 12. There is a non-linear benefit to avoiding deep discharge for your batteries (discharging half as deep might make them last 4x as long, not just 2x as long).

...

This is among the least ambitious, and therefor most realistic projects I've seen anyone attempt. You've good chances of pulling this off, and getting it done really really cheap if you start now and do a little bit every day.
 

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Discussion Starter #5
Before anything, thanks for giving such a fleshed out reply to my bare bones plan. I didn't even consider using prius parts (when i really should have) and I realize that I have some more research to do before getting into this. Reading through this though, I have a few questions :

Alternatively, buy a 2nd or 3rd gen Prius transaxle for ~$150-$300. No engine, just the transaxle.
Where would one source axles to connect to the transaxle? I doubt that the axles from either a civic/crx or a prius would fit in cleanly. Sounds like an absolute headache to sort out.

A Prius inverter ($150-300) will suffice as a DC motor drive, which might be your cheapest option. You'll need some control circuitry from the Open Inverter forums. I don't know if it's popular enough yet that anyone's selling any board for it, but it's been tested.
Assuming the inverter is essentially the motor controller, this does seem like the best option in terms of cost effectiveness. My concern is that I don't know if I will be able to put it all together properly.

While saving money where possible is the goal, I would also like the project to be as easy as possible. I don't really have the tools to hack together an adapter plate at my house. This limits my options to buying an existing adapter plate (and therefore a motor that fits) or picking up whatever motor i can, modeling an adapter plate myself, and getting it CNC'd. I also asked for an off the shelf option for a motor because california is still currently in a lockdown (more or less). I was planning out a conversion similar to what Benjamin Nelson did in his videos.
 

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Where would one source axles to connect to the transaxle? I doubt that the axles from either a civic/crx or a prius would fit in cleanly. Sounds like an absolute headache to sort out.
I don't know. Cheap transaxle projects are mostly a new thing from this last year.

I presume they take both axles to a machine shop or a driveshaft shop and say "make these fit"

Assuming the inverter is essentially the motor controller, this does seem like the best option in terms of cost effectiveness. My concern is that I don't know if I will be able to put it all together properly.
Yes, inverter is a speed controller for AC motors. You have to invert DC into sine waves, which is a positive pulse and a negative (or inverted) pulse.

This is no more complicated that a Curtis controller. You buy the Prius inverter, buy the control board, plug it in, connect your inputs (pedal, break, ignition, battery, etc)... and you're done. A little bit of variables to tweak for your particular motor (following a procedure) and you're done.

The Prius Gen3 is currently easier than the gen 2, and has more features, but Gen3s are more expensive and have a flaw so you're more likely to find a dud.

The Gen2 is all through-hole components and easy enough for a first-time soldering project if you start with the easy components first.

While saving money where possible is the goal, I would also like the project to be as easy as possible. I don't really have the tools to hack together an adapter plate at my house.
What tools do you have?

You need a drill and jigsaw, and a cheap runout indicator. You could squeeze by with a hacksaw too I guess, or a sawzall, maaaabye a circular saw but it won't be pretty. You could squeeze by, by just spinning it by hand and feeling for the balance point (no vibration). All you reaaaally need is a drill.

You're adjusting it by the width of a piece of paper which seems tough, but it's the point where the vibration stops. I could link you a couple videos showing how it's done without a dial indicator. It takes a few minutes. When you find the sweet spot you stop, clamp it tight, and drill your matching holes. Ta da.

If you want an off the shelf motor and an off the shelf adapter plate, I think you're stuck with Volkswagon beetles and you'll blow your whole budget right then and there.

... You're probably not getting out of this without some metalworking. You'll probably need a welder and grinder. I suppose you could use wood, for how ghetto and limited your goals are, but... if cutting a shape out of aluminum scares you into wanting to buy off the shelf, you'll have to pay everyone to do everything for you and your budget won't be enough.
 

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What tools do you have?
Basically some screw drivers and a few socket wrenches. The main problem is that I would have to buy a lot of tools that I would only use a couple times

You're probably not getting out of this without some metalworking. You'll probably need a welder and grinder. I suppose you could use wood, for how ghetto and limited your goals are, but... if cutting a shape out of aluminum scares you into wanting to buy off the shelf, you'll have to pay everyone to do everything for you and your budget won't be enough.
I don't really know anyone with metalworking experience let alone someone with the tools. I would like to learn some fabrication but the entry fee is too high. I was planning to get by by roughly dropping the motor (transaxle) in, modeling engine mounts/adapter, and getting it done elsewhere.

Is there any projects using this prius transaxle/inverter swap you could point me towards? Seeing the process would help me out a lot.
 

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Basically some screw drivers and a few socket wrenches. The main problem is that I would have to buy a lot of tools that I would only use a couple times
You're somewhat defeating the purpose of a learning experience project.

There's all kinds of tactile skills that you won't get from a computer. New tools and learning how to use them, having them around for future projects seems like it should be something you at least have a passing interest in, if you're going into engineering.

We're not talking about thousands of dollars in tools here. You want to build a car without a drill, and pay someone to do everything?

You don't know anyone who owns a drill you can borrow?

You want to be an engineer, and take on a project that shows your aptitude for it, yet plan to never in your life own or use a drill?

Yeesh. I dunno that that's a wise path for you.

But okay, look up if there's a tool library or a makerspace in your city you can join. Even if they're closed right now, there's probably someone in the community who'd lend you their crappy old tools when the time is right.

Or check Craigslist or your facebook marketpages.

Doesn't have to be fancy, an old corded drill is fine.

You're going to run out of budget if you want to pay for literally everything being done on the vehicle except for nuts and bolts. You seem to want someone else to build the vehicle and you just want to make some 3d sketches and then drive it afterwards a few times before whisking yourself off to a top-10 school.

Makes you a bit of a poser, no? You want to sell the image that you have a passion for engineering, but you actually... don't. You don't care for the process, to learn, or even have the end result. You just want to look like you do.

Go to Habor Freight and buy:
- the cheapest flux core welder they have,
- an auto-darkening mask
- Leather gloves
- the shittiest angle grinder and some spare zip discs and grinding blades
- drill
- soldering iron
- hacksaw

It'll be a couple/three hundred bucks for the lot.

If you're not interested in owning those... you've set yourself up for such interesting constraints I'm not sure many people are going to be able to give you advice.
 

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Is there any projects using this prius transaxle/inverter swap you could point me towards? Seeing the process would help me out a lot.
It's been very popular with Teslas and Leafs.

Prius is just starting to hit completion on some projects. Kevin Sharpe's company hosts Damein in Ireland to do weekend courses (10 people each) teaching them how to convert using a Prius transaxle, they've been running that monthly for half a year now.

The Open Inverter forums might help you out a bit more there.

I haven't followed it too closely since I'm not building my vehicle like that.
 

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Makes you a bit of a poser, no? You want to sell the image that you have a passion for engineering, but you actually... don't. You don't care for the process, to learn, or even have the end result. You just want to look like you do.
In the end, I'm making up excuses to try to avoid doing the fabrication because I'm scared that I'll sink to much money into something that I don't really know anything about. Physically pulling the trigger on this project has been pretty hard for me in general.

That being said, I do have in interest in trying this out but I just have a lot of reservations. I just want to have a solid plan before jumping into this.

I've been looking through Damien Maguire's videos and the prius inverter is probably the best and cheapest choice I have available to me. The fact that its a Controller and a dc to dc converter all for around $535 USD is unbeatable. My question is what a good AC motor would be. The only budget AC motor I can think of (without using prius transaxle with custom axles) would be the nissan leaf motor. At that point, would it better to use the nissan leaf controller?

Another question is if I should go for higher voltage (seeing as the batteries im going to use are $10 a pop)
 

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In the end, I'm making up excuses to try to avoid doing the fabrication because I'm scared that I'll sink to much money into something that I don't really know anything about.
I hear ya.

$5000 is a lot of money for something you don't care about, and you just hope to use to get into a different college.

I'd suggest building something you might actually use, or be usable. If that's enough to commute around in for college, then good. If your only expansion is going to be to buy better batteries for more range later, that's still a useful project.

My question is what a good AC motor would be.
I got mine out of a forklift. I don't know if I've seen anyone else using an AC forklift motor for a project.

Mine was free. I don't recommend it.

Go with solved problems if you can. Use a Prius Gen2 or Gen3 transaxle if you can.

A leaf motor is nicer but it's overkill for your shitty car.

By using an existing transaxle you're trading off dodging the hassle of a coupler, with adding the hassle of making the suspension and such match, or something. I don't know, I'm not knowledgeable much about suspension work, Brian might be able to offer better advice.

Another question is if I should go for higher voltage (seeing as the batteries im going to use are $10 a pop)
The Prius inverter is good for up to 550v I think. But the Prius pack itself only has 200v. If you want to use the DC/DC, you'll have to be above 110v or so. Higher voltage is generally better, no reason not to keep going.

...

Things are moving fast. Since I last gave you advice, 3 big developments:

1 - Damien finished his Prius Gen3 kit thing and started making a video tutorial. If you can't buy them already, you will be able to very very soon.

2 - Johannes designed and ordered a Prius Gen2 kit, to arrive and be tested soon. He ran a batch of 10 so if they work, they should be for sale soon.

3 - Damien finally got around to ordering his Prius Gen2 DC motor controller boards, they've arrived, he's yet to test them. He's got 10, so, they'll be up for sale soon too.

...

If you're concerned about the motor you could just grab the pump motor from a DC forklift, which will be smaller and light, and use it to turn the existing transaxle in your shitty Civic. You'd have to create a mounting plate and some kind of coupler, or pay for that to be done. But that's just about it. Use Damien's Prius Gen2 DC controller, you won't find anything else cheaper.

Damien has a 1000 pound-sterling build on his channel (including the price of the car). You can't follow that exactly, as, you just won't come across the same resources Damien does and you're probably not as charismatic. But it has lots of good details about all the extra fiddleybits you'll need to pick up and use. Contactors, vacuum pump, gas pedal, etc.

...

On the subject of crappy batteries, I decided to see how good or bad my own advice was last week. I called up the biggest auto store that sells batteries to people I could think of, and asked them if I could buy their old batteries for the core charge. They hemmed and hawed and said no, it all goes into a system and blah blah. I said they could leave them aside as they come in, so they never enter the system, and then I pay them for them. I didn't try very hard, nor in person, so I got mostly rejected there.

Then I called NAPA and asked. They were reluctant and asked what they were for, I said "a science project". Manager said sure. I specified that they'd have to be decent batteries, maybe 2/3 of the CCA they were rated for, and asked if I could come in and test them. Manager said no, that's okay, they'll charge and test them. It'll probably take a couple weeks to accumulate how many I asked for (3 normal size, 3 motorbike sized) that were worth using.

So, 1/2. However, their core charge was $20 CAD.

Costco is $10 CAD, but I don't have a membership so I didn't call.

NAPA is a poor choice. People who shop there fix their own cars. Their dead batteries are probably actually dead. You want ignorant consumer shops that get their battery tested as part of their regular oil change service, get told it's time for a new one, and say yes. Those are going to have the best used batteries.

But you probably want neither of those sources, I thought of a better one. Call up alarm or fire certification services places. Maybe a smaller guy, but not too small. (Small has more freedom and less rules, but larger will have access to bigger jobs). Alarm batteries typically get replaced on a schedule, not on a need basis. For liability reasons, they'll just be on a schedule, every 2 years, 3 years, whatever it is, and the rule will be that every battery in the building gets replaced, no point in testing, it's not worth the administrative hassle.

Condo projects (every hallway, every 50 feet in the parkade) will have lots. Office buildings. Etc.

Most of these batteries literally only get used during the annual light-out fire inspection to make sure they can power the emergency egress lights. They should be functionally virgin, and there's only a few form factors.

You could ask them to set aside good batteries of a specific common form factor. The core charge is probably cheap, but ask and check. They may just send them straight to a scrapyard rather than return them for core charge, I've seen whole pallets of identical alarm batteries at recyclers.

The good thing about UPS / Alarm / Etc batteries is that they'll be deep cycle too, with literally zero cycles below 95% full in their lives. So you can get deep cycle batteries which are way better than starter batteries for your application. And, with smaller form factor, you can get to a higher voltage easier, and higher is better (better top speed, more choices about where to pack them).

Anyway, food for thought.
 

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Discussion Starter #12
If you're concerned about the motor you could just grab the pump motor from a DC forklift, which will be smaller and light, and use it to turn the existing transaxle in your shitty Civic.
Wouldn't you have to use a ac to dc converter to do this? The problem I foresee with using the prius inverter is the fact that you are forced into using a 3 phase ac motor.

Use Damien's Prius Gen2 DC controller, you won't find anything else cheaper.
Any notable differences between gen 2 and gen 3 inverters? There is a negligible difference in price on ebay and I cant find any prius's on classifieds that are being parted out.

As for batteries, I found a listing on craigslist for a bunch of old batteries pulled out of an old ev, but since I dont know the whether sealed batteries are still semi usable after a long time of non use I havent pulled the trigger.
https://sfbay.craigslist.org/sby/pts/d/los-gatos-lead-acid-batteries-ah-and/7125714663.html

Another thing I have some questions about is the wiring. I was under the impression that you could use the existing fusebox in a car to power all the 12v odds and ends that you needed but judging by most of the wiring diagrams I've looked up so far, it seems that everything is wired individually.
 
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