Dreamers Questions. Hillclimb 4wd Racer

Technical discussion on converting internal combustion to electric
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Dburto1btw
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Dreamers Questions. Hillclimb 4wd Racer

Post by Dburto1btw » Sat, 21 Oct 2017, 18:20

Hello ladies and gentleman

My name is Daniel Burton and I own a company called Burton's Tube Worx.

I have a few questions to ask regarding some ideas ive had with building hybrid racing car similar to the Porsche 919 Le Mans Car.
https://newsroom.porsche.com/en/motorsp ... 12724.html

Im building a hill climb racer from scratch and im in the CAD design faze of my build.
My company will be fabricating the entire build in-house so changes can happen fluidly and hopefully cheaper.

The design at the moment is essentially like any formula car with rear wheel drive and a mid engine layout.
Its designed to run a transverse mounted turbo Hayabusa 1300cc engine and gearbox with a chain to a final drive.
The longest run time i will be doing is approximately a minute plus i need reversing power when in the pits from one of the electric motors

My idea is to run one of these electric motors http://emrax.com/products/emrax-268/#14 ... 2c2ea-c5c5 mated to a final drive at the front of the car to make it 4wd.
Also to add something along the lines of a KERS system for the rear wheels to fill in any power gaps

My question is whether i need to run a massive battery to give it all power

or

Can i run a small battery like on of these https://www.elmofo.com.au/lithium-batteries.html and use a generator mated to some kind of constant speed drive to keep it powered.

Knowing the answer to these questions will answer packaging concerns and will help me change it to suit the job at hand.

Thank you to anyone that can shed some light on this. I am in no way an electrical engineer so please help a stupid fabricator.


Cheers

Daniel Burton
Chief Technical Officer
Burton's Tube Worx

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Re: Dreamers Questions. Feel free to call me an idiot.

Post by jonescg » Sat, 21 Oct 2017, 19:07

Sounds like a fun project. If the purpose is hill climbing, I'd say go full electric rather than a hybrid. Hybrids have been done before, but they are not common - check out Elmofo's Nissan project for example.

The Emrax motor is a popular choice but there are a few points to consider; mainly it is a giant outrunner which means you will have to take care in packaging the motor. Also, it's a liquid cooled stator which was optimised for adding propulsion to a glider. There's lots of cool air for keeping things happy at 2000 m, but in a car it's a different story. You may find it will de-rate considerably without such airflow. But power to weight, and dollar per kW it's pretty good on paper.

An alternative motor would be the Phi-Power motors (including the Evo motor replacement - PhE38x). I use the 381 in the race bike and it's a massively powerful motor which has never let us down.

And you don't need to be an engineer to build cool projects! There's always room to learn.

Cheers,
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Re: Dreamers Questions. Hillclimb 4wd Racer

Post by Dburto1btw » Mon, 23 Oct 2017, 11:59

Cheers for your reply jonesscg.


I had considered going full EV but it would exclude me from running in Formula Libre 'RACE' and 'SPEED' classes and would turn my car into an exhibition with no cars to run against in my area. Its a shame because i love the idea of electric vehicles. The chassis has been designed to run in a variety of high aero, single seater classes and also has provisions for the use of a full electric system eventually when others start running too.

I want to be able to disengage or remove the 4wd system from the front of the car to be able to meet the Formula libre 'race' regulations which exclude 4wd systems and to meet the formula libre speed regulations i want to make the electric power system selectable so that i can use it out of low speed corners, parts of the course with low grip, off the line for acceleration, etc.
Im hoping that with the system being selectable that i will be allowed to race in the speed classes as a hybrid and be included with the other cars

I couldnt find any information on the ELMOFO R33 except that it had a electric boost system.

I assume you mentioned the packaging with the outrunner due to more rotating mass. If so that makes good sense not to use it. A large enough outrunner like that would presumably have a pretty large gyroscopic effect? Could affect the handling in the front of the car if so.

The Phi-power motor looks like it would be better if its more suited to EV's and wont have that gyroscopic effect being an in runner.

Did you happen to have any of the answers to my questions above. Contrary to popular opinion autistic people aren't all good at maths as proved by myself. lol

Cheers for reading and for any help you can provide.


Daniel Burton
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Burton's Tube Worx

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Richo
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Re: Dreamers Questions. Hillclimb 4wd Racer

Post by Richo » Mon, 23 Oct 2017, 12:55

Dburto1btw wrote:
Sat, 21 Oct 2017, 18:20
My question is whether i need to run a massive battery to give it all power or

Can i run a small battery like on of these https://www.elmofo.com.au/lithium-batteries.html and use a generator mated to some kind of constant speed drive to keep it powered.
The elmofo batts appear to be rated to 15C.
$3750 for ~30kW peak, 19kg 1865Wh.
Claimed to be the most "ENERGY" dense.

Well really for this application you want the most "POWER" dense.
TBH for short racing li-po is more in line.
For about the same 30kW it would be $350, 5kg, 580Wh.

If you run 230kW for 60secs thats 3833Wh.
So 2 elmofo batts would get the energy but NOT the power (60kW). $7500 38kg
Lipo ~$2700 4446Wh 38kg 230kW

I wouldn't bother with a generator for a 1min race?!?
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Re: Dreamers Questions. Hillclimb 4wd Racer

Post by Richo » Mon, 23 Oct 2017, 13:06

Dburto1btw wrote:
Mon, 23 Oct 2017, 11:59
I assume you mentioned the packaging with the outrunner due to more rotating mass. If so that makes good sense not to use it. A large enough outrunner like that would presumably have a pretty large gyroscopic effect? Could affect the handling in the front of the car if so.

The Phi-power motor looks like it would be better if its more suited to EV's and wont have that gyroscopic effect being an in runner.
I doubt there would much difference between the outrunner or Phi motor in terms of gyroscopic forces.
It's just an issue having the whole outer case spinning form a mechanical assembly point of view.
I'm sure you could cope with either...
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Re: Dreamers Questions. Hillclimb 4wd Racer

Post by jonescg » Mon, 23 Oct 2017, 14:15

I'd agree with Richo - power is what you need for short format racing. Lithium cobalt chemistry is perfect for the job as it's got reasonably good specific energy (150-160 Wh/kg) and very high specific power (>6 kW/kg).

Either motor can be made to work - the Emrax will just need a bit more thought as to how to direct airflow over the rotor. The rotational inertia won't be that big a difference.

I can see what you mean about having the versatility of a hybrid, but there's nothing stopping you from building a very fast car capable of at least 100 km range either. It just won't be cheap, but hey, that's racing...
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Re: Dreamers Questions. Hillclimb 4wd Racer

Post by Richo » Tue, 24 Oct 2017, 12:33

Also when considering lipo some of them only have 100-200 cycles.
Although the quoted >6000 cycles for the elmofo battery is only at 1C not racing 15C so that could easily drop to 1000 cycles.

So $2700 for 200 cycles would be $13.5 PER RACE.
$13.50/minute - I hope racing is better than a hooker :lol:

I'd never consider lipo for anything other than racing as for a regular road car it works out to like $58/100km!
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Re: Dreamers Questions. Hillclimb 4wd Racer

Post by mikedufty » Wed, 25 Oct 2017, 10:44

I got about 400 cycles (5000km) out of the first set of lipo model aircraft batteries on my e-bike. Mostly at around 1C. Second set are still going OK at 7000km/500 cycles. Not a huge lifespan, but they are very small and light and cheap, so good for that application. I don't think I'd want to be replacing the i-MiEV battery twice a year, but on the bike it is a 5 minute job, costs under $100 and keeps me going for a year or two.

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Re: Dreamers Questions. Hillclimb 4wd Racer

Post by Dburto1btw » Wed, 25 Oct 2017, 19:33

I would like to say thank you all very much for your detailed replies. Im learning a lot just from looking up some of the things your saying i dont understand.

So i think from your replies i would be needing to go with a lithium cobalt battery that has enough power and energy to do the job im after without the added weight of an onboard generator. I will use the EMRAX 268 motor i listed above i think. It has the correct dimensions to fit in such a small area in the nose of the car behind the crash structure and will also be easy to fit in the rear of the car.

100 km range should be enough to do a sprint race in formula libre. Thats 14 laps of Bathurst or 22 laps of SMP. Rippa!!!

Any recommendations as to what battery brand and size i should be looking at for the hill climb running two of these EMRAX 268 motors http://emrax.com/products/emrax-268/#14 ... 92c2ea-c5c

Id like something with some reliability if possible.

Also hypothetically what battery/s would i need for doing the 100km's?

Im not to worried about the cost of running it to be honest. Once you factor in tyres, fuel, accomodation, travel, hookers, etc. lol $15 is a small cost in my eyes. I will probably only use two batteries for the life of the car so its hopefully worth the cost.

Cheers again fellas. This info is helping me alot. I will be posting the progress on here and a race car building forum once it starts.

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Re: Dreamers Questions. Hillclimb 4wd Racer

Post by jonescg » Wed, 25 Oct 2017, 20:13

14 laps of Bathurst at 80 km/h. Maybe 4 at full race pace.
If you want 100 km range at normal road going pace, then 20-30 kWh would work. This will drop to about 40 km as soon as you put the hammer down because speed kills range.
I put lithium cobalt packs together if you're interested - not cheap, but well built.
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Re: Dreamers Questions. Hillclimb 4wd Racer

Post by Dburto1btw » Thu, 26 Oct 2017, 10:32

Cheers for that info mikedufty.

Ah ok. I thought you meant for race pace in that other post. I should have put two and two together. lol.

What would you charge for a battery pack for my application Jonesscg? Also what would a company charge me if you dont mind me asking?

Also ive been reading aboit lithium cobalt batteries. Are they dangerous? Everything i read is saying they can be quite dangerous. Are you fellas talking about the LiFePO4 batteries or the LiCoO2 batteries?

Cheers. :)

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Re: Dreamers Questions. Hillclimb 4wd Racer

Post by jonescg » Thu, 26 Oct 2017, 10:44

LiFePO4 cells are safer for sure, but they lack the energy density we desire for a road-going EV. I think most LiFePO4 cells are 110 Wh/kg at best.
However within LiFePO4 is a range of capabilities, including very high discharge rates (30C) and very low rates (think yellow Thundersky cells etc).

LiCoO2 cells are more volatile, but with great power comes great responsibility :) 200 Wh/kg + is possible. And even 180 Wh/kg with 20C discharge rates are possible. This chemistry comes in both pouch cells and cylindrical cells, but I find cylindrical cells a PITA to work with - lots of spot-welding and they do get warm under modest rates (1 to 3C).

LiNiMnCoO2 (commonly called NMC) is a popular choice as it's a compromise of energy density and power, but no more or less safe than LiCoO2. It comes in pouches or cylinders and is in the 1C-3C range for discharge.

I build packs using 5 Ah pouch cells and put these inside either a polycarbonate or aluminium enclosure. They end up costing about $1120 per kWh excluding GST. This also doesn't include the enclosure (as this is normally heavily customised) and the BMS choice is up to you. Happy to help, but I also appreciate that the cost is significant.
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Re: Dreamers Questions. Hillclimb 4wd Racer

Post by Dburto1btw » Fri, 27 Oct 2017, 19:38

Ok. Cool. Thats excellent information chaps.

So i should be using the LiCoO2 chemistry for this application for the ultimate in Wh/kg with applicable disharge rates.

So i guess this gets us back to the basis of my original questions.

What approximate size/area of battery will i need to run the two motors for 1 minute @ full power and 1 of the motors in the pits for 2min at 25km/h max?

I am a way off from actually building the car but i will definitly want you to build the battery if your still willing when its time jonescg.

I really appreciate this help gentleman. This electric drive system is a linch pin in the design and this info will really help the progression of the car.

Cheers. :)

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Re: Dreamers Questions. Hillclimb 4wd Racer

Post by jonescg » Fri, 27 Oct 2017, 20:18

Hey we're all here to help!

Definitely choose the motor and inverter first. That's the heart of it all - the electric moor is what makes the EV such a dream to drive/ride. Pick the power you want and make sure the motor spins in the right range for your final reduction. For a car with a 3.5:1 or 4.2:1 differential, that's probably about 6000 rpm. Then pair that motor with an appropriate inverter. The most valuable number here is the torque constant, or Kt. This will let you know how much torque per amp of phase current you can expect, and from that, you can size the inverter and battery.

Most inverters and AC motors are optimised to run on either a 400 V DC bus or a 650 V DC bus. You can get lower voltage systems, but there seems to be a sweet spot over about 350 V DC.
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Re: Dreamers Questions. Hillclimb 4wd Racer

Post by Richo » Mon, 30 Oct 2017, 12:42

Dburto1btw wrote:
Fri, 27 Oct 2017, 19:38
What approximate size/area of battery will i need to run the two motors for 1 minute @ full power and 1 of the motors in the pits for 2min at 25km/h max?
Planning is the most important part - even before you buy anything or pick up a tool.
If you run 230kW for 60secs that's 3833Wh.
So running 2 motors 460kW for 60sec is 7666Wh

An estimate would be 4kW for 25kph.
So that would be 134Wh for 2minutes.

Total 7800Wh used.
But for ~80%DOD you would be looking at a 10kWh pack size total.
$6,100 86kg 40L 500kWpeak.
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Re: Dreamers Questions. Hillclimb 4wd Racer

Post by Dburto1btw » Thu, 02 Nov 2017, 22:26

Ok. So the only problem im gonna have now is weight. Its gonna be tipping the scales at 160 odd kilos for batteries, motors etc. So im thinking i will need some track information. The track that uses the highest and longest throttle percentage should be my aim i guess. Im gonna have to find someone with a data logger fitted that doesnt mind filling me. That can help me lighten the battery/s by knowing how much power i need. I think

My dad always said "The only stupid question is the one you didnt ask." So in that vain. I have another question. Lol.

Could i go without a battery all together and use the engine hooked to a generator to power the electric motors? Or is that something that makes no sense. Please tell my why if so.

Cheers again lads this help is invaluable.

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Re: Dreamers Questions. Hillclimb 4wd Racer

Post by jonescg » Fri, 03 Nov 2017, 12:19

Re: generator-motor, you'd be better off leaving a gas engine in there if you take that approach.

Re: battery - yes I'd say a 16 kWh, 150 kg battery is about right for most hillclimb/burnout activities. The Mitsubishi iMiEV has a 16 kWh battery and it has a range of 100 km at responsible road speeds. I think it weighs in at about 1100 kg. No reason you can't get your race car under 900 kg either - It should still go like a rocket.
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Re: Dreamers Questions. Hillclimb 4wd Racer

Post by Richo » Fri, 03 Nov 2017, 12:46

Dburto1btw wrote:
Thu, 02 Nov 2017, 22:26
Could i go without a battery all together and use the engine hooked to a generator to power the electric motors? Or is that something that makes no sense. Please tell my why if so.
Ok so you need a 460kW generator ie 2 electric motors 230kW ea to produce the electricity.
Then you need a petrol motor with a surplus 500kW of mechanical power.

The battery weighs like 80kg.
I doubt you could get a generator and petrol motor to do 500kW under 80kg.
Not to mention the cost.

If you had a 500kW petrol motor then would be no point adding electric motors to it at all.
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Re: Dreamers Questions. Hillclimb 4wd Racer

Post by Richo » Fri, 03 Nov 2017, 12:53

jonescg wrote:
Fri, 03 Nov 2017, 12:19
Re: battery - yes I'd say a 16 kWh, 150 kg battery is about right for most hillclimb/burnout activities.

No I think he means 150kg for the whole system.
80kg battery (10kWh Lipo)
40kg 2xERmax268 motors
30kg other crud - couplers, controllers, wires etc

A datalogger with GPS+G sensors my help trim down the actual requirements.
But running 460kW peak will mean there will always be a minimum battery pack size.
And it wont be much smaller than what I have already said.

The only way you can reduce this is to reduce the peak power.
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Re: Dreamers Questions. Hillclimb 4wd Racer

Post by jonescg » Fri, 03 Nov 2017, 15:19

Yeah we had a 9 kWh battery on Voltron and it would have put out ~190 kW to the rear wheel. The current 6 kWh pack puts out 175 kW to the wheel.
I'm just thinking he might want the extra capacity in order to get to the event sort of thing. The added power of a big pack would certainly help but the weight is a detractor.
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