[brian_]

- 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.

 

[brian_]

... 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.

 

[brian_]

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.

 

[brian_]

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.

 

[brian_]

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.

 

[brian_]

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.

 

[brian_]

Keep in mind that more batteries will increase charging time, assuming that charge rate is held constant.

On the other hand, a larger battery will accept a greater rate of charge, so if the constraint is how quickly you can get a fixed amount of energy into the battery (rather than how fast a battery can be fully charged), a bigger battery is better. For example, a 100 kWh battery could charge at 50 kW for an hour (from 25% to 75% charged), while a 50 kWh battery would not be able to sustain 50 kW all the way from 0% charged to 100% charged.

As with everything else in life, and especially technical design, it's a compromise.

 

[brian_]

The OP is talking about going fast, over 100 MPH at least (he says "sub-120 MPH).

Ah, I remember the original "fundraiser rally" description and forgot about that. Certainly up to 120 MPH (or even the sustained 80 MPH actually expected) means lots of power... and an unreasonable event. A long distance road rally is generally an open-road event, so it cannot safely or legally operate at high speed. High speed performance rallying is fast... and occurs on closed road for short distances.

All things being equal at 100 MPH the car will be using 4 times the power as it will be at 50 MPH because of the inverse-square law.

He's going to need literally as many batteries as possible.

I agree. Except that it's four times the aerodynamic drag (and therefore four times the energy used to overcome aero drag per distance travelled), and so eight times the power. Of course all drag and therefore all energy needed to move the vehicle isn't aerodynamic drag; rolling resistance and mechanical friction are roughly constant forces, so energy per unit distance for that component is roughly constant and power varies in direct proportion with speed.

The goal of this build is crossing countries. When Stated sub 120mph, I meant to say we're not building this car to compete with the speeds tesla's are capable of. Sustained 80 - 90 mph is probably more the goal.
The real race (when driven along with ICE Cars) is limiting stopped charging time. So that's our goal along with creating a more Aerodynamic car than any Tesla.
...
500KG batteries is really stretching it, so less may be more desirable. The real race, as said, is minimizing charge time.

With stops designed for cars burning fuel, 500 kg of battery will likely be too low to make it to the next stop, rather than too high.

 

[brian_]

Despite Brian's comment today Tesla's have a higher efficiency than any of their competitors in terms of energy usage per mile

In the published claims, yes. In real-world testing, not so much. And those are complete vehicles being tested, not just motors and controllers, so the actual efficiency of the motors is unknown for most motors.

There's nothing wrong with Tesla efficiency, and it's probably better now that they have caught up with the rest of the world and use permanent magnet synchronous motors, but there's also nothing magical about it.

 

[brian_]

Is that what the leaf motor is?

Yes - PMAC. If you tear down a Leaf motor and a Tesla Model 3 rear motor, you can see that internally they are nearly identical.

 

[brian_]

You might be disappointed with the Leaf motor View attachment 127526

The top speed of any single-gear-ratio EV is determined directly by the maximum motor speed, the gearing, and the tire circumference. The top speed of a Leaf is not a failure of the vehicle or a limitation on another vehicle using the motor, it is the consequence of good design: choosing the lowest gear ratio (most reduction) which allows the vehicle to reach the highest required speed. There's no reason to drive a Leaf over 90 MPH, so the gearing isn't taller.

If you use an absolutely stock Leaf drive unit but want to go fast, use taller tires. You can also provide more battery voltage to extend the top of the motor's performance, within inverter limits for voltage and bearing limits for mechanical speed.

 

[brian_]

Yup, for sure. Engineer it for the application. If you can safely get 34% more speed with bigger tires then that'll work. Or a combination of more voltage and bigger tires. A 500V nominal system will likely achieve that too with a motor speed of 13400rpm, if it can survive mechanically, electrically and thermally.

OP wants to go up to 120mph in a race...

The initial comment about speed was

...
So charge fast, drive fast (sub 120mph). And efficient

but that was later clarified to

... When Stated sub 120mph, I meant to say we're not building this car to compete with the speeds tesla's are capable of. Sustained 80 - 90 mph is probably more the goal.

... so even stock Leaf speed could work, and not much more would be needed.

 

[brian_]

Tha advantage of the Civic is we can start with the bare shell and not add luxury's.
In the leaf we are bound by complex electronics and their weight.

What luxury items or "complex electronics" are there in a Leaf that you couldn't remove from the Leaf and would not need to add to the Civic to make it run as an EV?

 

[brian_]

Can-bus, doorlocks, modules, full wiring harness, Abs, stability program, safety electronics, aircon, multimedia, you know...modern technology...

You need CAN-bus communications to operate the Leaf components that you will using, regardless of what car they're in. The rest could be deleted from any EV, and will exist to some extent in the Civic. All are trivial compared to the EV battery. Build what you want; I'm just suggesting that you be realistic about what the result will weigh.

 

[brian_]

A controller that regulates the workings of the inverter/ motor. Like an the ECU for an engine. Just a single controller to drive the car.

These are commonly called a "VCU" (vehicle control unit) in EV conversions, and are offered for the most common drive units & inverters, which are the old Model S/X induction units, the Nissan Leaf, and now the Tesla Model 3.

Another example is the Dilithium VCU from Thunderstruck; that's not an endorsement at all, just the first example that came to mind with a supplier link.

 

[brian_]

What would be the ideal rev range for the LEAF motor?
If one had a gearbox to remain in this range... View attachment 127604

Looking at this diagram I would say between 4k and 8k rpm.

Yes, the ideal speed depends on the power requirement, but that's the range.

The field weakening starts as soon as 2800rpm?

No, the break at 2800 RPM doesn't have anything to do with field weakening - it is where the line of constant torque at low speed resulting from the motor or inverter's current limit intersects with the line of constant power at moderate speeds imposed to protect the battery, so the system goes from current-limited to power-limited.

No idea which EM57 version this represents

The form of the data doesn't change much - if at all - between Leaf versions. What changes are the current and power limits. The top edge of the operating range shown in this graph is 80 kW (about 20 Nm @ 2800 RPM, or 80 Nm @ 9800 RPM, or any other combination on the hyperbolic curve between those points), indicating that this is from a motor and controller from a Leaf with 24 kWh or 30 kWh battery (the first generation of Leaf, model years 2011-2017). A later motor and controller combination will look similar but extending further out to the curve corresponding to 110 kW (with 40 kWh battery) or 160 kW (with 62 kWh battery).

 

[brian_]

Assumption: Tesla batteries are most energydense. ... They charge faster & more efficient than alternatives. (I believe this was stated on a YouTube channel).

There's all sorts of nonsense on YouTube channels. Unless someone provides test data, I would assume that they are just repeating rumours.

 

[brian_]

Well, my idea was to swap the trunk pack at charging Points. I read somewhere (this is successfully attempted before) that a different pack runs a different BMS and needs to be physically connected and disconnected from the inverter. At that Point you disconnect the other pack.

You're describing two packs which are used as two separate batteries, only one at a time connected to the inverter. That fixes the problem of connecting two packs at dissimilar voltages to each other, but how does the built-in (not swappable) pack ever get charged?

But any battery that Runs on empty is Dead weight.

It's even worse than that. Using two half-sized batteries instead of one whole-sized battery means that whenever you are using or charging a battery, you're doing it at double the rate (relative to battery capacity)... which is less efficient.

You're designing a solution to a problem which is very specific to your use - which is why no production EV does this - so to get the right solution you need to understand your specific situation very well. By that I mean having a very specific plan for distance travelled, energy consumed, and peak power required for each leg between service locations, and how much time and charging power is available at those locations.