# 85kwh model s pack emrax 268 design ideas/advice



## sanjuga (Feb 12, 2016)

here's some more direct questions

will the outrunner motor need a bearing block to add extras support or can i attach a cv joint directly to the floating face of the motor?










can i run the motors and batteries in a single cooling loop?

something like this: Motor>Radiator>battery>motor>radiator>battery>motor>radiator>battery etc.

the tesla modules have cooling input and output at one end and electrical connections at the other

what would be the best config to try and isolate bus bars from cooling tubes

red lines are bus bars, blue lines are cooling, in the front and rear module i cant isolate cooling from electrical,


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## RIPPERTON (Jan 26, 2010)

In this case because there are no radial loads on the motor you wont have to put a bearing to support the inner CV joint but I would get rid of the central motor mount frame and motor mounts and have 2 smaller plates spaced apart so there is a common room between the 2 plates for cables and cooling hoses. The motors would be the same distance apart as they are now.

PS you could actually get rid of all 3 of those bulkheads and replace them with 2 plates of say 10mm aircraft alloy pocketed.


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## sanjuga (Feb 12, 2016)

yeh that sounds like a much better solution, i think it will still need two plates outside of the motors to mount the wishbones to though

unless the plates are made larger, but you also lose quite alot of rigidity by only having the 2 central plates


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## sanjuga (Feb 12, 2016)

its looking like a better solution will be to have each pair of motors cooled by their own radiator plus one radiator for all inverters and one radiator for the batterypack 

i would like to implement a system that can change the cooling loops if needed, some kind of solenoid valve manifold to regulate temperature of all components


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## Tomdb (Jan 28, 2013)

Why go more complex with the cooling then needed? This will all just be weight and things that can go wrong.
I would believe having a reduction will help you out in the long run, tweaking the reduction so you get the best torques spread. Tires will want to light up at any speed, however You might want more torque lets say above 100km/h due to downforce coming into effect.

Is there a reason for wanting to have it a two seater? Otherwise go full out for the Palatov d1 setup, battery pack riding shotgun.
I also believe that having the battery spread out like that will give you issues in the long run, no way to easily wire it all up, HV and bms, plus the cooling loop will be crazy.


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## dougingraham (Jul 26, 2011)

The Tesla batteries are not a good choice unless you want to go a long distance. They are energy cells instead of power cells. You need to have too many of them paralleled to get the power. You are needing 4 * 75 kW peak. The Tesla pack at full charge is just over 400 volts and sags pretty badly under load. Nominal voltage is 355.2 and it probably sags 25% under an 850 amp load.

You might be able to combine the battery and motor/inverter cooling loops. Depends on if you can get the heat out of the coolant.

Best Wishes on your project!


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## jwiger (Oct 18, 2014)

I agree with Doug on the cooling. As long as you can get enough heat out that you're not sabotaging components further down the line.

I would recommend a bearing to protect the motor from side loads though. When CV or U joints are flexed, they want to straighten out. It's a trick that is taken advantage of in old school drag racing with leaf springs. If it's enough to lift the back end of a old school Plymouth GTX a few inches, then it will play havoc on motors.


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## sanjuga (Feb 12, 2016)

do you know what the discharge specs on the tesla cells are?

i thought with a 96s 74p pack, and an 850 amp load, its only 11 amps per cell?


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## dougingraham (Jul 26, 2011)

sanjuga said:


> do you know what the discharge specs on the tesla cells are?
> 
> i thought with a 96s 74p pack, and an 850 amp load, its only 11 amps per cell?


Yes, 11.5 amps on a 3.250 ah cell is 3.5C and if you look at the chart for a Panasonic NCR18650B cells (which is what many people believe they are using) you see pretty terrible sag. Like I said in an earlier post, these are energy cells and are great for going long distances, but not so great for power output.

KMAN (look for his channel on youtube) is going to do some testing on a couple of actual Tesla cells soon.

I have not seen the inside a 90 kWh pack yet. I am guessing is looks just like the 85 but they use a little different cell with a little better characteristics both power and energy.

The tradeoff is energy or power. They want to go a long way. If you are racing you are generally more concerned about power and weight.


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## sanjuga (Feb 12, 2016)

ok, so why do tesla use these cells, doesnt the model s have terrible sag?

they have 300kw of motors and 96s 74p pack, i dont get why your adverse to the tesla cells 

imagine a model s that weighs 800kg thats what i would be trying to achieve

whats currently on the market that would perform better? a samsung 30q pack?

tomdb, i have been thinking about your recommendations, heres a single emrax 348 motor design, single seater even more like the palatov, it would use lsd's front and back driven by chains, this would simplyfly things lots, but would be losing out on the individual wheel control, which attracted me to the 4 motor design










and 4 motor single seater:










i expect it would work out cheaper and easier, what do you guys think the disadvantage would be like on the track, between

a car with 4 motors, torque vectoring, regen brake vectoring, and 300kw, 1600nm 

and a car with a single motor, mechanical diffs, no torque vectoring, no brake vectoring, 300kw, 1000nm


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## Tomdb (Jan 28, 2013)

I would go two motors. One front one rear. Keep the drivetrain simple.

The sag you can live with, how ever pounding the amps back into the batteries will be the issue.

Depending on what kind of tracks you want to run, and what events you could tune your battery motor combo. Getting a right balance between torque and topspeed so you are not missing on the bottom or top end.
If its time attack runs go with some http://ampahaulic.com/ ampahaulic cells. 

However chevy volt packs can also be pushed hard, check out that thread, http://www.diyelectriccar.com/forums/showthread.php/2012-chevy-volt-battery-93101.html
I believe these packs are the best preformance per dollar when in need of amps.


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## dougingraham (Jul 26, 2011)

sanjuga said:


> ok, so why do tesla use these cells, doesnt the model s have terrible sag?
> 
> they have 300kw of motors and 96s 74p pack, i dont get why your adverse to the tesla cells


Yes the Model S has terrible sag at full load. However the intention of the car is to go 250 miles over a 4 hour period. This is a C/4 load on the cells which means the design goal is not 12 amps per cell loading but 813 ma per cell average (60 amps at a 60 mph cruise). I am not adverse to the cells Tesla used. They are just not necessarily appropriate for your application.



sanjuga said:


> imagine a model s that weighs 800kg thats what i would be trying to achieve


If long range is your goal then there is nothing wrong with the Tesla cells. But if you can maintain the ratio of vehicle weight to battery weight your battery must weigh about 1/4 of that of the vehicle. This means a 200kg battery. Which means about 1/2 of a Tesla pack or about 40kwh. And if you reduce the size of the Tesla pack in half you have reduced the peak power output to 1/2 of what Tesla can do. 

You keep mentioning track use and the Tesla model S and Roadster are not known for their performance on the track. They can sort of drag race but only because the races are so short. If you do too much you will overheat the cells and you end up with a huge cooling issue. If you are talking Tesla model S peak power levels you need the whole pack and the Tesla pack contains 16 modules that each weigh about 24.5 kg for a total of 392 kg. Can you design a car where half the mass is the batteries? How much energy do you need? How much power do you need? Those are the key questions in determining the battery. Energy equates to range and power to acceleration and top speed.


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## sanjuga (Feb 12, 2016)

the chevy volt packs look good, the different sized modules puts me off though
what kind of motor could be run? could it do 150kw?

say two volt packs running 2 150kw motors, front and rear, that sounds good

it would give the ability to change torque bias between front and rear better than nothing i suppose

what kind of drive time could i expect from 2 volt packs driving hard with 300kw of motors? thats only 32kwh vs teslas 85kwh seems like a big compromise in capacity for roughly similar module weights

doug i didnt realize the tesla would overheat from hard driving, doesnt it just limit its output to cooldown a little?


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## Tomdb (Jan 28, 2013)

Again this would all depend on track. Ratio accel to decel to coast.

Got some simulations on a 1600kg electric race car doing laps of the Nurburgring Nordschleife, doing roughly 800-1000wh an lap. Track is 21 km roughly, so 21kwh for an lap. This was with next to no regen simulated. 

I would figure in at 600wh/km-800wh/km, on 2 volt packs, 16 x 2 kwh, 40-50km on charge.

I would run two 268 emrax motors highvoltage versions.


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## dougingraham (Jul 26, 2011)

sanjuga said:


> doug i didnt realize the tesla would overheat from hard driving, doesnt it just limit its output to cooldown a little?


It limits power if the motor and inverter are hot. Probably it knows just how much heat it can shed and how much is generated. I just have a regular 85 kw Model S and at the 80 mph (129 kph) allowed on the local highways it never power limits. I've seen video of extended autobahn runs at 200 kph where the current limiting bar shows up. On tracks I think regen is one of the things that is a problem. Because on the track you are either accelerating or decelerating and regen heats the motor/inverter too so no chance to cool down.

If you read carefully you find that the Ludicrous mode Teslas are not limited by the motors but by the battery output. And from what I have read the insane and Ludicrous mode cars are no faster than the regular ones when you get below half charge. Too much voltage sag on the pack.

You have an ambitious project here. I wish you the best.


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## sanjuga (Feb 12, 2016)

here is the best i can think of for a dual 268 motor with 8 chevy volt 24s modules










chain driven would be simplest because you could just buy the whole suspension and differential setup from palatov


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## jwiger (Oct 18, 2014)

I'm looking at the manual for that motor. 
http://www.enstroj.si/images/stories/manual_for_emrax_motor_december_2014_new.pdf

Page 12 says the continuous power output of the motor is 50-90hp with combined cooling. Is that enough power per motor to do what you want to do?


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## Tomdb (Jan 28, 2013)

Did some solidworks layout.
Using my old Hybrid layout as a starting point. This one has a differential, with two Emrax 268's attached. the gas engine is a r1 engine. The battery is modeled as 3 4 kwh volt modules. And again two Emrax motors upfront I would build this in a heartbeat if I had the cash, ofcourse engineering the details before investing.

For the ev conversion, I removed a rear emrax motor and moved the other to the input of the differential. Then added more volt modules, depending on your desired wheelbase these can be behind the driver. Just to give you an idea.

Wheelbase is 2000mm, the tire tracks are now 1700mm (1800mm outside width)

Edit: Since I had solidworks fired up, I loaded in a haynes chassis and mocked up a two motor 4wd ev using chevy volt modules. So far this also looks like a quite feasible route. 
A haynes/locost 7 roller have been known to weight between 350-450kg depending on the exact spec. So a car below the 800kg should be easily achievable. Plus this chassis is quite proven and easily built.


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## Karter2 (Nov 17, 2011)

dougingraham said:


> Yes, 11.5 amps on a 3.250 ah cell is 3.5C and if you look at the chart for a Panasonic NCR18650B cells (which is what many people believe they are using) you see pretty terrible sag. Like I said in an earlier post, these are energy cells and are great for going long distances, but not so great for power output.
> 
> KMAN (look for his channel on youtube) is going to do some testing on a couple of actual Tesla cells soon.
> 
> ...


 The guys reselling the Tesla cells are convinced they are the Panasonic 18650BE cell, identified by its unique circular indent mark on the base. 
These are from 85S and P85D packs, which incidentally weigh over 600kg in thier complete cased form with all cooling and interconnects etc.
But again even the BE cell is only rated at 3 amps continuous !.....but it is almost indestructible ( eg, Discharge to 0 volts doesn't damage it !)
However, There are much better cells if you need high output.
EG :- Samsung 25R, Sony VT 5, LG HE2, etc
Tesla cells are chosen for life cycle, capacity, reliability, etc....rather than ultimate performance. 
Performance would be the likes of A123, Saft, etc as used by the F1 teams.


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## sanjuga (Feb 12, 2016)

its looking more and more like batteries arnt economically viable for this project yet.

i need watercooled modules that can give high peak power

tesla modules are no good

a123 and saft im sure will be beyond my budget, 

other 18650 like samsung, are also beyond my budget, not to mention the complexity of making the modules with water cooling

the chevy volt batteries look good but the size, shape and weight for the capacity isnt ideal

maybe in a year or 2 the market will have improved

the 2017 chevy bolt pack looks good, especially if it can output 300kw like the volt pack, does anyone know the specs of this pack, is it the same chemistry as the volt pack?










also possibly whatever comes out of the gigafactory? 20700 cells?

are tesla planning to create modules the same size as their 444 cell 18650 modules with 20700 cells so they can upgrade the modules in the model s

may just have to wait until some better batteries enter the salvage system


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## Karter2 (Nov 17, 2011)

Ahh !.. A common problem !
The plan is good, the technology exists, ..there is just one problem..
..a mismatch between desire and budget !


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## sanjuga (Feb 12, 2016)

Karter2 said:


> Ahh !.. A common problem !
> The plan is good, the technology exists, ..there is just one problem..
> ..a mismatch between desire and budget !


can you suggest a 400v, ~400kg battery solution that can output 300kw peak? for under $10,000?

i dont think the plan is good yet


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## Duncan (Dec 8, 2008)

sanjuga said:


> can you suggest a 400v, ~400kg battery solution that can output 300kw peak? for under $10,000?


Yep - two Chevy Volt packs - about 400Kg,
over 300Kw peak and about $5000


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## Tomdb (Jan 28, 2013)

This may also be achievable with two nissan leaf packs, however these are not watercooled so, the thermals will be harder for a racing application.

You could always get into 18650's however the making of suitable modules will take alot of work or money.


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## Karter2 (Nov 17, 2011)

There are several options that could deliver 300kW @ 400v for under $10k...
But that isn't a very full specification.
3.0 kWhrs of John Metrics cells would meet that requirement..with change, ...and weigh less than 50kg !
But I suspect a few more KWhrs may be in the plan ?


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## sanjuga (Feb 12, 2016)

nissan leaf is a no go without watercooling, 

chevy volt is good but an awkward shape not quite got the capacity i would like

chevy bolt pack looks perfect if it can do a similar discharge to the volt pack


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## dougingraham (Jul 26, 2011)

sanjuga said:


> chevy bolt pack looks perfect if it can do a similar discharge to the volt pack


I am guessing that it could a few times. But they are going to be using energy cells to keep the weight down. They don't need power cells because they have such a large pack that it can make the power they need anyway.

Racing places a lot higher stress on the components. Especially when you factor in Regen. You are either drawing out a lot of power or you are putting back in a lot of power. No time to rest, no time to cool off. If all you were doing is drag racing then that is different. 10 seconds of huge grunt, no regen needed, several minutes rest before you could possibly do it again. Easy.

I suspect the Volt batteries would not like racing behavior too much. You would need to parallel them to get the load down to typical driving levels if you want them to last.


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## sanjuga (Feb 12, 2016)

2 volt packs vs a bolt pack, im just guessing the dimensions of the bolt pack based on a cell profile of 100mm x 340mm

2 x 228 motors front 2:1 gearing

1 x 348 motor rear driving lsd

seating position is more like an f1 car with feet up in the air

would it be beneficial to run the volt packs in parallel with 32kwh at 400v or series and upping the voltage with 16kwh?

if the batteries are warrantied for 8years? then surely they would last more than a few cycles? i suppose the driver would have to monitor the battery temperature and drive accordingly?


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## P0IS0N (Feb 19, 2016)

You could wait for the Emrax 348T, here's what the guys on Estroj are saying: "We are also preparing documentation for EMRAX 348T, with folowing specifications: torque 2000 Nm, power 600 kWp, weight 70 kg, dimensions: dia 348 mm, lenght 170 mm."
I have no idea what inverter, controller and battery pack you would need for that one.


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