DIY Electric Car Forums banner
1 - 20 of 86 Posts

·
Registered
Joined
·
35 Posts
Discussion Starter · #1 · (Edited)
Hello you awesome people,

I'm on the hunt for lots of info to build a very special car with very special needs.
Our small team wants to build a specific car to raise funds for an organization focused on children's wellbeing.

Of course we need to check the viability and cost involved, to inform our sponsors. You could consider this a charity start-up.

The team is technically, mechanically, and fabricationally (is that even a word?) skilled. Help is all around us.

The car in question is a 90's compact car, small petrol engine, manual gearbox, fwd, 1000kg driveable. It has a smaller tire size. (185cm circumference).

The Aerodynamics will be taken care of to bring it to much higher levels of efficiency.
The car will be purpose built, so no extra weight, no luxery for the driver... Basically, an empty shell to build on.

The car will be used for international long distance Road rallies. (+10h driving) The goal is to have a large range, short charging time, and high speeds. Since the end goal is the lowest time to arrival.
So charge fast, drive fast (sub 120mph). And efficient

I am a petrolhead at heart and this electric stuff is very new to me.. but basically the build has yet to start so we are open to any direction regarding parts etc.
So here are the questions I hope you can answer before we continue.

Efficiency factors:

- tire size, does it make much of a difference to change circumference / width
(To like i3, 155 wide, 220cm circumference).
I know it does with an ICE, so I'm guessing YES

- is there an efficient rev range in electric motors?

- size of motor or way of driving for longest range?

- most efficient air / water cooled Netgain?
HyPer9 is available in Europe.

- any other motors you would advise? Preferably available with controller as pack

- gearbox or direct drive? (HyPer9 diff 1:5 or 1:7)
See also 2nd question/ efficient rev range

- gearbox with straight cut gears worth the investment?

- is rwd more efficient in EV's ( enough to convert, because I could)?

- I understand Tesla units are the most efficient, but need a very expensive controller? And they are also aircooled?

Range:

- size & type of battery pack (I'm thinking Tesla all day long?)
You guys probably can advise when the weight outweighs the advantages of range.
I think the car could haul about 16 Tesla modules.
We would love to surpass 400miles range.

- is a 130v motor more/less efficient than a 400v with the same battery pack (say 16 cells, differently connected of course )

- dual packs, dual loading system? Halve the charging time.

- what would be the charging (stopped) time, and to what % would you advise loading?

- is it possible to add an extra pack when a very long run is planned? (I don't mean plug&play, since there is cooling etc...)

- solar panels on car efficient? kWh?

Thank you for answering all the previous.
I thought it was best to ask most questions at once, instead of scattered throughout the thread.
There is, however, more to come.

Can you please advise before we proceed so we can steer this build in the right direction before electrifying?
We really need the expertise on this forum to succeed...
We would thus like to eliminate most of trial&error and go straight to Kick-Ass build/ end product.

I have been reading A LOT already (most of it on this forum, love the Wiki), please excuse me for wanting to repeat the same questions (if that sort of thing annoys you). But I would rather have all the answers in one place to document.

That way we can anticipate (and stretch) the budget.
And this makes it also possible for everybody interested or involved to understand the complete build (not just the person who did al the research. aka myself) and form their opninions on all the options and considerations. Hopefully you all understand.

So hey, what would be the setup of YOUR dreams for our goals?

Thank you all very very much!
 

·
Registered
Joined
·
7,950 Posts
- tire size, does it make much of a difference to change circumference / width
(To like i3, 155 wide, 220cm circumference).
I know it does with an ICE, so I'm guessing YES
Width matters - more width is more drag. Overall diameter doesn't matter much; aspect ratio and tire construction are more important.

- is there an efficient rev range in electric motors?
Not a single specific speed range applying to all motors in general - that would make no physical sense. For any given motor there is an optimal combination of speed and load, with all other combinations less efficient. Just do a web search for something like "Nissan Leaf motor efficiency map" to see examples (showing best efficiency in roughly the middle of the speed range and at the full load allowed by the controller), since the Leaf is well studied and reported. Other motors will have other optimal points.

- most efficient air / water cooled Netgain?
HyPer9 is available in Europe.
Why limit the choice to NetGain, a company which doesn't make any modern motors? The HyPer9, which they buy from Dana TM4, is the only modern motor that they sell.

- any other motors you would advise? Preferably available with controller as pack
Nearly any motor will be sold with a controller, or one or more controllers will be suggested as suitable matches.

- gearbox with straight cut gears worth the investment?
For efficiency? I suggest doing some searching to see if you can find an objective measurement of transmission efficiency which shows any difference at all between straight-cut and helical gears.

- is rwd more efficient in EV's ( enough to convert, because I could)?
Compared to front wheel drive, rear wheel drive has handling advantages, and of course a traction advantage in rear-heavy vehicles. Neither is inherently more efficient.

- I understand Tesla units are the most efficient...
If you've swallowed that nonsense, you need to forget anything you've heard about Tesla from Tesla fanatics, and instead look at objective facts.

And they are also aircooled?
No, no modern EV has an air-cooled motor.

- is a 130v motor more/less efficient than a 400v with the same battery pack (say 16 cells, differently connected of course )
No. There is no inherently best voltage for efficiency. You need to look at specific motors to meet your needs, and the what voltage they would need to operate properly.

But motor voltages as low as 130 V are just to make projects easier for small industrial vehicles and DIY conversions - no production EV or even hybrid would go that low, just because they couldn't get adequate motor performance at that voltage.

- solar panels on car efficient? kWh?
What do you mean by "kWh?" in this question? A panel is limited in the power it can deliver; there is no energy value associated with a panel. And it's rarely worth the cost to mount a solar panel on a vehicle.
 

·
Registered
Joined
·
35 Posts
Discussion Starter · #4 · (Edited)
You'll get more funds into the children's hands by handing over the project money.

Your goals are impossible. 10h rally with an electric? No way.
Well where's the fun in that?
+ There is no way sponsors will pay anywhere near the same amounts without publicity involved ...

I'm sorry I should have stated the rallies are 10+h of driving time NOT including charging stops.
Hence the other questions. Because we would like to somehow keep up with the pace.

Therefore we are exploring the possibility to twin charge separate packs in public chargers
 

·
Registered
Joined
·
35 Posts
Discussion Starter · #5 · (Edited)
Thank you brian_ (y)
The hyper 9 is just easy available here. There is also a watercooled option.

We will take a look at the leaf motor specs and availability here.

Is it doable to couple several Original battery packs together? Say 2x 40kw leaf batteries. Does this require a special controller?
 

·
Registered
Joined
·
35 Posts
Discussion Starter · #6 ·
So I've been reading up on the leaf option.
It seems they are available at around €2000.

It is not an option to buy a complete car and transfer all the gear. So what would we need to source extra?
From what I read
  • there is a need for an external controller. But the complete drivetrain from charger to inverter and motor + "drive gear" is useable
  • the external controller only works from my2013 (correct?)

What would be the build sheet with a complete Leaf drivetrain with self made battery packs.

Would it be adviseable to ditch the charger and install another one? Or is that insane.
The height of the complete assembly may pose a problem. And they are cheaper without charger on top

In any case, the Leaf route seems a viable option.
 

·
Registered
1996 Toyota Land Cruiser
Joined
·
488 Posts
Aero drag will be your biggest nemesis at those high speeds. Everything else will be secondary. If you don't already have a car I suggest a convertible, then chop off the windshield and build a tonneau cover around everything but the driver and a small windshield like a 50s racecar. Otherwise you might consider chopping the windshield and lowering the roofline of whatever vehicle you choose. Frontal area is frontal area and you need to minimize it.
 

·
Registered
Joined
·
1,759 Posts
I might suggest ECOMODDER as an aero forum for design parameters.

Recent data suggests short charge times from not draining the pack is more effective use of stops.

Two words GEO metro or equivalent aero vehicle as the base, perhaps a honda cvrx. 90's weren't noticeable aero efficient.

Whatever you do, it will be a kludge, ask Elon.
 

·
Registered
Joined
·
35 Posts
Discussion Starter · #9 ·
Thanks guys for your input

The aero side of things we've got covered.
I've read the books, watched the video's, joined the ecomodder forum recently (long time lurker) and the team is very skilled to make it all happen.

So now we've got to cover the Driveline side of things.

Electric land cruiser, you have the leaf engine right?
 

·
Registered
Joined
·
7,950 Posts
... Two words GEO metro or equivalent aero vehicle as the base, perhaps a honda cvrx. 90's weren't noticeable aero efficient.
A CRX? Yes, they're very good for their time, although that was decades ago. There's an active first generation CRX conversion project in the forum now, and recent second-generation CRX project.
 

·
Registered
1996 Toyota Land Cruiser
Joined
·
488 Posts
Thanks guys for your input

The aero side of things we've got covered.
I've read the books, watched the video's, joined the ecomodder forum recently (long time lurker) and the team is very skilled to make it all happen.

So now we've got to cover the Driveline side of things.

Electric land cruiser, you have the leaf engine right?
Yes I'm using a LEAF motor as well as other parts and a Resolve-EV controller. It would be a good choice for you IMO as you could drop the FWD drivetrain in the front of another FWD car pretty easily. Also as to your question which is better FWD or RWD. It doesn't matter if the drivetrain is the same but typically RWD cars use a drive shaft and rear differential which reduce efficiency quite a bit. On the other hand RWD cars like the MR2 or Fiero use the same drivetrain as a FWD car, just in the back. Those have the same efficiency as a typical FWD car. For your project whatever is easiest, lightest, and simplest is best.

Do you have a vehicle yet or are you still looking?
 

·
Registered
Joined
·
287 Posts
If you can fit 16 modules, then you should be using a Tesla drive unit. More efficient and more powerful than a low-voltage motor, plus then you just have series connections at the module level, which is more reliable.

16 modules, Tesla small drive unit, no gearbox (drive unit has an integrated differential), no onboard charger (weight reduction). DC fast charging is actually simpler on the vehicle side as all the high voltage AC/DC conversion circuitry is handled by the fast charging station.

You could probably get 400 miles of range with such a setup. Possibly more.
 

·
Registered
Joined
·
7,950 Posts
A drive shaft makes little difference to efficiency, but the final drive of a traditional front engine and rear wheel drive system typically uses a hypoid ring and pinion gear set, which is less efficient than the non-hypoid bevel gear that could be used, or the parallel gear set that a transverse engine or motor configuration uses.
 

·
Registered
Joined
·
35 Posts
Discussion Starter · #14 ·
Yes I'm using a LEAF motor as well as other parts and a Resolve-EV controller. It would be a good choice for you IMO as you could drop the FWD drivetrain in the front of another FWD car pretty easily. Also as to your question which is better FWD or RWD. It doesn't matter if the drivetrain is the same but typically RWD cars use a drive shaft and rear differential which reduce efficiency quite a bit. On the other hand RWD cars like the MR2 or Fiero use the same drivetrain as a FWD car, just in the back. Those have the same efficiency as a typical FWD car. For your project whatever is easiest, lightest, and simplest is best.

Do you have a vehicle yet or are you still looking?
Well in fwd you always have the extra losses (=less efficient) because of the angles the driveshafts turn at. Percentage-wise this will be the same with an ICE or electric. I was just wondering how sensitive an electric drivetrain is to all of this. But then when wanting to maximize range I guess I answered my own question. The other option is to transversely mount the engine in the back axle as you suggest. But I would rather stay away from all this.
Fabricating difficulties aside this sounds like a nightmare to legalize for road use.

We are dead set on a car but still have to buy the right example.
 

·
Registered
Joined
·
287 Posts
Thank you brian_ (y)
The hyper 9 is just easy available here. There is also a watercooled option.

We will take a look at the leaf motor specs and availability here.

Is it doable to couple several Original battery packs together? Say 2x 40kw leaf batteries. Does this require a special controller?
Leaf batteries have heat dissipation problems, they're just passively cooled. You'll run into problems if you try to charge them up quickly (DC fast charging). Leaf motors are good though. Leaf motor and tesla modules is a range-maximizing combination. Leaf motors are also cheap and simple.
 

·
Registered
Joined
·
7,950 Posts
Tesla components are no more efficient than every other events manufacturer's components, and they all run at roughly 360 volts, or on a few cases about twice that. There's not much difference in efficiency between a modern EV motor and a modern lower-voltage motor (such as the Dana TM4 motor sold by NetGain as the HyPer 9), but lower voltage means higher current and thus more power loss in wiring unless massive conductors are used.

I didn't get the impression that high power is required. Carrying more motor than needed and more battery than needed is a weight and therefore efficiency issue.

An onboard charger could be eliminated, as long as the car can be charged at service stops as needed. Without an onboard AC charger, that means compatible DC charging consistently available.
 

·
Registered
Joined
·
7,950 Posts
Well in fwd you always have the extra losses (=less efficient) because of the angles the driveshafts turn at. Percentage-wise this will be the same with an ICE or electric. I was just wondering how sensitive an electric drivetrain is to all of this. But then when wanting to maximize range I guess I answered my own question. The other option is to transversely mount the engine in the back axle as you suggest...
What angles do you think are involved? If you mean the changing angles of the half shaft CV joints due to suspension movement, you'll have that with any suspension, unless you mount a motor directly on a beam axle (and I don't suggest that). If you mean the changing angles of the half shaft CV joints due to steering, it's not a meaningful issue.
 

·
Registered
Joined
·
35 Posts
Discussion Starter · #18 ·
If you can fit 16 modules, then you should be using a Tesla drive unit. More efficient and more powerful than a low-voltage motor, plus then you just have series connections at the module level, which is more reliable.

16 modules, Tesla small drive unit, no gearbox (drive unit has an integrated differential), no onboard charger (weight reduction). DC fast charging is actually simpler on the vehicle side as all the high voltage AC/DC conversion circuitry is handled by the fast charging station.

You could probably get 400 miles of range with such a setup. Possibly more.
Do we need a separate controller?
 

·
Registered
Joined
·
7,950 Posts
Do we need a separate controller?
Every motor needs a controller; in an AC motor that includes an inverter. In the Tesla case and now most others, the controller/inverter assembly is mounted directly to the motor or transaxle. The two common approaches to using salvaged EV motors (including any model of Tesla) are:
  1. use the original inverter/controller with an aftermarket external device which manages computer network (CAN) messages; or,
  2. use the original inverter with the controller (logic) board replaced an aftermarket or DIY board which controls the inverter.
 
1 - 20 of 86 Posts
Top