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Discussion Starter #1
I am a beginner. I owned a 1967 Mustang so I have some knowledge on cars. I am a mechanical engineering student so I plan to use this project to apply what I'm learning to something. And this will be a major project. I plan to spend around 15-20k in total on this build. I want this to be a quality build to get a reliable ev - I basically want a modern vehicle when it comes to driving and handling with the classic look so I thought EV would be the easiest way to get that combo.

The donor car is a 1978 Corvette with the stock auto. transmission - I hope to use the trans but I might go direct drive depending on what you all recommend (I don't know much about conversions and haven't been able to find too much info on direct drive vs. auto trans).

The plan is to use two Warp9 NetGain motors at 144v. The motors will be connected by an adaptor and they will be joined at the shaft.
Parts I plan on buying are:
1 x DC/DC Converter 400W 30 Amp
1 x Dual Motor Adapter for NetGain 9"
1 x Adjustable Temperature Fan & Pump Switch
1 x Charger
1 x HPEVS Curtis 144V 650 AMP Controller
1 x NetGain Speed Sensor
1 x Throttle Box
I know it's not a complete list, the rest will be bought with the batteries.

I need recommendations on batteries and other parts to buy. I want a sports car since this is a 1978 Corvette and I want range. It would be nice to get 100 miles a charge, but realistically I would want 40 - 50 miles since I'll probably be going pretty fast.

All of this is still in the development stages so all ideas are welcome. The main goal of this conversion is to have a daily driver that will put a smile on my face when I push on the accelerator. I want a fun fast car basically.

Thank you for your help,
EvC3/Sunvette
 

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You don't specify your range/performance plans which limits our ability to make recommendations, but a very good source for EV conversion batteries these days is wrecked nissan leafs. You could get a 24kwh nominal battery with a good C-rate for a few thousand that way. Just buy from a reliable source or verify the health of the pack while still in the donor car before handing over money.

Soliton and Zilla are the only dual motor capable DC motor controller manufacturers I know about.

A good strategy when doing a build is buy the batteries as LATE as possible in the process. Make cardboard mockups or something else to take their place during the design and build stage.
 

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Discussion Starter #5
Thanks for replying. Are there any similar builds with part lists that I could read as guidance?
 

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I changed the controller I just forgot to tranfer it in my journal.
What controller are you going with then?

I'm not sure it makes much sense to go with a 144V system if you have dual motors. That means you will have to wire the motors in parallel, which diminishes some of the advantages of having two motors.
 

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Sounds like a fun project!

With two WarP 9's you can get by without the automatic transmission. Make one of them a transwarp 9 and then you can tie it to the drive shaft and position the motors in the transmission tunnel.

The one disadvantage of elimination of the transmission is that you will need to provide a way to electrically reverse the motors. The Zilla has a direct way to do this.

You can do several different arrangements depending on how much power you want.

1) Use a battery with around 340 volts and a single 1000 amp controller. Wire the motors in series. A high voltage Zilla 1K can drive this arrangement with around 340 kw input to the motors. This would give you about 500 ft-lbs of torque and a WHP of around 300. This is a fairly safe peak power level from the motors standpoint for up to 30 seconds or so. Since cruising power at 60 MPH is around 20 kw (27 HP) the motors would be loafing on the highway. In this case the battery would need to be able provide a peak current of 1000 amps at something over 300 volts. Each motor will see around 150 volts at 1000 amps. In that car this should give performance similar to a Tesla.

2) Use a battery with around 340 volts and a single 2000 amp controller. As above wire the motors in series. A high voltage Zilla 2k can drive this arrangement with around 680 kw input to the motors. This would give you over 1000 ft-lbs of torque and a WHP of around 600. This is for really short duration use of perhaps 15 seconds. And like the one above your normal use case is motors loafing along. Each motor will see around 150 volts at 2000 amps. To operate at these currents you will probably need to do the Helwig brush holder upgrades on both motors. This arrangement would give performance far exceeding the Tesla ludicrous mode.

3) Use a battery with around 200 sagged volts and two 2000 amp controllers. Each motor is wired to its own controller. You would need a pair of high voltage Zilla 2k controllers. Each motor will be driven to 384 kw or a total of 1029 input HP. Again this would give you around 1000 ft-lbs but the peak WHP would be a little higher. And of course you would need to use the Helwig brush holder upgrade to keep from killing the motors.

There are other arrangements offering similar levels of performance but those are the most straightforward.

Your problem with the above is going to be batteries. I think you would need at least 3 of the Leaf packs paralleled to do the number 1 setup and 6 or 7 to do the others. And you don't have room or weight budget for this. On the plus side you would have plenty of range if you could fit even 3 of them in the car. Three of the leaf packs would be a 72 kwh pack and give around 200 miles of range.

I will leave the battery discussion until later.
 

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Discussion Starter #8
Thank you for your replies again. I decided to go with the Zilla 2K motor controller. Dougingraham's second option sounds most like what I want to do. Do I need to get the 72 kWh and 340v to get that power? Also, since I have the Zilla 2K controller, would a direct drove system be better to do?

Thanks for your help - I hope to get this project started soon.
 

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Thank you for your replies again. I decided to go with the Zilla 2K motor controller. Dougingraham's second option sounds most like what I want to do. Do I need to get the 72 kWh and 340v to get that power? Also, since I have the Zilla 2K controller, would a direct drove system be better to do?
This is more about expectations than anything else. If you want a car that feels quicker than it was with the original ICE you can get that with a single Warp 9 and a 1000 amp controller and tie it to the original transmission. How can this be? A WarP 9 puts out ~250 ft-lbs at 1000 amps and a peak input HP of 230 HP. It has to do with how that torque is delivered. An electric motor delivers the torque at Zero rpm up to around 4000 rpm. The ICE motors used in 1978 on this car delivered between 175 to 220 HP depending on options. With gasoline engines the torque tends to track with the HP figure. The difference is that the torque in an ICE is a curve that peaks somewhere between 3000 and 5000 rpm and drops off dramatically on either side of the peak. At Zero RPM an ICE has zero torque. Tricks are used just to get the car moving. A flywheel to store the energy and then a clutch that you can slip and very low gears to boost the torque. In the case of an automatic you have the torque converter to replace the slipping clutch. With an electric motor everyone finds that the lowest gear is pretty much completely worthless. A single WarP 9 would have a peak output power of around 185 HP so it is in the range of the original engines for Peak HP but the torque is higher over a wider rpm band.

Adding the second motor is the key that doubles the torque giving you effectively an apparent power output that looks like more than a 500 HP ICE would give you. And it gives it to you from Zero to around 4000 rpm which means you can get rid of the gearbox as well. This is going to be a seriously fast car. For a recent example look at the Zombie 222 which is a dual motor setup. Or for an older example look at the White Zombie which weighs about half of what your car will weigh.

The problem with batteries is that even lithium batteries are heavy and bulky when you start to talk about these kinds of power levels. If we look at the Leaf pack we see a pack with a nominal voltage of 355 volts (3.7 volts per cell or 7.4 volts per module) and an AH capacity of 66.2. This gives a 23.5 kwh pack (Nissan calls it 24 kwh). Nissan in the Leaf pulls a peak current of around 300 amps which is about 5C. This is why I suggest the need for 3 in parallel to have a similar load on the battery at 1000 amps. It may be that a single pack could do 10C which still means two in parallel. Three minimum would be prudent. If you elected to use two you could limit the performance to that of the battery. This would be 600 battery amps at 300 volts would still be a peak HP into the motors of 180 kw (241 input HP). You would still set the motor current to 1000 amps and would still see full torque at the lower RPM's It would probably limit the torque curve to around 3000 rpm or maybe a bit less than that instead of 4000 rpm. A pack under the trunk where the fuel tank was and one under the hood would give a decent weight balance. I have heard of the Leaf packs going for around $2500 each. The pack weighs about 650 lbs so with two of them you are talking about 1300 lbs.

If you want to use LiFe type batteries you need enough capacity to get 2000 amps. This means at least 200 AH of cells so you can do 10C briefly. The CALB CA cells would be able to do this. You would need to parallel 100 AH cells to get there. And to get 340 volts you need to put 100 in series. This would be a nominal 320 volt pack and 64 kwh. It would weigh over 1500 lbs and cost around $25000. Your weight and $ budgets are completely blown.

The highest power batteries are the high C hobby packs. John Metric sells these for drag racing purposes with heavy wire in a convenient size for building packs. Each module is 4.5 ah and can do about 450 amps (100C) for a few seconds. But they sag a lot at 450 amps so if you were to use these for street purposes you would probably want to limit them to 50C or 225 amps each. This means you need to parallel 9 to get the amp rating you need. Each module has six 4.2 volt cells in series so they have a peak voltage of 25.2 volts but are considered to have a nominal voltage of 22.2 volts. To get your 360 volts peak for the Zilla means 16 in series. 16 in series times nine in parallel gives 144 modules. This is a pack of 14.4 kwh and would weigh 230 lbs for the cells. That is the good news. Your range would be around 41 miles with this pack. Neither good nor bad. Doubling that would give 81 miles range and the batteries would never be stressed. Cost for each module is $120 so the 144 module pack would be $17280. I have spent a LOT of time looking at this and for convenience I bought 29 packs from John. I will be using 28 in my car so one of those is a spare. You could trade a lot of extra work for perhaps 25% cost savings if you were to buy the packs in a more granular form from the discount hobby retailers. The other downside of these packs (besides cost) is that if you use them for daily driving and use a significant amount of the charge you are looking at only 300 cycles of life. For drag racing this is more than likely 3000 to 5000 runs down the drag strip. I did 19 runs down the 1/8th mile strip a year ago. Lets say you could do 20 per day at 4000 runs this would be 200 days at the drag strip. Basically a lifetime of racing.

I don't know what to suggest. A heavy car is not going to corner well. I expect that you could fit three Leaf packs in the car if you can suffer the weight. You might consider a staged approach. One motor into the transmission with one leaf pack. The car will be light and agile Probably lighter than with the ICE. It will be quicker off the line than the original car. If that is not enough pull the transmission and add a second motor and battery. Add a third battery and turn up the current. Change your mind and pull the third battery and turn the current back down.

Good luck! I look forward to watching your build.
 

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Hello,

I know this is an oldish thread, but I'm in the early stages of planning a pretty identical project as evc3. I'd like to ask dougingraham a few questions.

First, I'm looking at the simplest set up with a single Warp9 motor mounted to the original transmission (not sure if I'm going to find a manual or auto, though). I'd like to keep the weight down as much as possible, so I'm wondering if one leaf pack would be enough for ICE-similar performances, and a range of about 50 miles (when I'm not flooring it, of course).

Second, has there been significant changes in tech or battery availability since the last post?

Thanks!
 
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