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what’s the weight of the 25 kW DC electric motor?
Isn’ t a 3phase AC electric motor lighter, more efficient and reliable, even less costly ?
What about the life and the number of charge/discharge cycles of the lithium battery? Do you envisage to fully discharge it ?
Alessandro (Pisa, Italy)
The motor we used to drive from Darwin to Adelaide was a brushed DC motor, with a mass of about 40 kg. An AC induction motor would be lighter, more efficient and perhaps even cheaper, but requires a more complicated and more expensive controller.
A permanent magnet brushless motor is smaller, lighter and more efficient again. We have recently replaced our entire rear end with the swing-arm from a Vectrix scooter. The swing-arm, motor, reduction gear, wheel and tyre have a mass of about 27 kg. The motor is a permanent magnet brushless motor. More efficient, more reliable, but more expensive.
Our current (120 km range) lithium ion polymer battery has an estimated life of 250000 km. The new battery will be larger, and have an even longer life.
We have designed the car so that we do not (often) have to discharge beyond 80%.
Thanks for your response
Correct if I wrong,
but as far I know an induction motor is far lighter than ANY dc motor (besides the right arguments about expensive controllers and so on)
For example, the Tesla Roadster 3-phase, 4-poles AC motor is only ~ 30 kg but for a power of about 250 HP, much better (x 5) than the power density you envisage. Moreover, it doesn’ t need any permanent magnet and thus rare earths resources that it’s very likely they run out in the short term
You might be right about the mass of an induction motor. We should be comparing continuous power per mass, and it is not always easy to find the data. I was not able to find motor mass and continuous power figures on the Tesla web site. Brusa induction motors have continuous specific power of about 0.4–0.6 kW/kg. The Raser Technologies induction motor has 0.9 kW/kg. For permanent magnet machines, the UQM machines have continuous power density of 0.75–1.1 kW/kg. But there are large variations in specific power for both types of machine.
Tesla has an article comparing permanent magnet motors and induction motors.
Of course, Trev could use either type of motor. The difficulty for us was to find a low-mass, efficient motor that would operate at our chosen voltage (we were operating at 150 V, for historical reasons).
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up to 10 teams from around the world will take part at the Euro EV Race 2010 with their electric vehicles across Europe from October 3rd to 19th, 2010. We noticed your acitvity at the zero-race and thought that you might generally be interested in the Euro EV Race 2010.
If you are, we send you further details.
Best regards from europe
Euro EV Race 2010
Zero Race will still be running at the time of the Euro EV Race, and there is only one Trev (at the moment). However, we will watch your race with interest.
Hi, I am just going to answer one of Alexandro’s question..
this was the post he wrote:
“For example, the Tesla Roadster 3-phase, 4-poles AC motor is only ~ 30 kg but for a power of about 250 HP, much better (x 5) …”
Hi Alexandro, Tesla does have a 250Hp motor, but you have to take in account that they are watercooled, and have a radiator to dissipate the heat from both the motor and the traction inverter. This lowers the overall power density.
Then again, the inverters also weigh quite a considerable amount. Take in account of a Calmotor controller prototype GP450A,it weights 16kgs (just the controller, ignore the piping and the glycol solution flowing through it.)
btw that inverter costs around the region of $8k, but then you add your tuning of your AC motor, which is another $3k, and then add another $1.5k for diagnostic tools. So we are looking at around $13kUSD, without even the motor.
Now take in consideration of a Agni Motor, its Axial-brushed DC, yet upto 93% efficient. it weighs around 11 kgs, and produces 25Hp(1.7kW/kg) ( with proper clean airflow, and as much as 40Hp for around 40Seconds(tested on my electric Boat and Motorcycle).
As mater of fact,Considering only AIR COOLED motors, DC motors pack more power if properly designed and they are simpler, and lower cost.
Thats why you will see most EV conversions start with DC motor. Look at the White Zombie (Electric Car Dragster) that uses DC, not AC, or perm-mag
But DC are not the most efficient. The work efficiently near No-load. Thus for any application using DC, Bigger the motor, the more efficient it will be during usage.
But more comparative load, more is the loss.
I hope that clear’s out the confusion.
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Dear Trev Team,
We highly respect your diligent efforts and results, saw your movie driving through the AUSTR. desert, fantastic spirit. Working our GreenPowerTrike we transport 2 people side by side in complete comfort by pedal power or 250W pedelec assist for doing daily chores. More than 100 units have been sold and are used by triathlon people, veterans, physically habdicapped people, by hotels and resort places to be rented out to tourists. When can we expect that your high powered trike is ready for production and export?
Several of the Team Trev members have electric-assist bicycles. They are a great way to get around, and make cycling easier for long commutes or in hilly terrain. They are inexpensive to buy and operate (compared to cars or motorcycles), easy to use, simple, clean, quiet, and fun.
At the moment, Trev is a prototype only. More work would be required to get it to a stage where it could be manufactured and sold, and at the moment we do not have anyone working on this. However, we we are working on developing a kit-car version. Trevipedia has more details.
Is Trev back in Australia yet ?
Alan … waiting waiting
Trev was delivered to UniSA at the end of last week. We checked that the battery was still charged (it was) and gave it a quick drive around the workshop. We will be giving Trev a thorough check, and 30000 km service, next week.
How does one obtain a complete set of plans for the Trev?
We do not have a complete up-to-date set of plans for Trev, because Trev has been modified several times and is still not perfect. But we are, with the help of volunteers, creating a set of plans. Take a look at http://trevipedia.net/ .
Do you have a BOM for the front supension?
Best regards, Dan
Originally we designed and built our own suspension, but did not have enough movement for the rough roads we were likely to encounter driving around the world. We modified the front suspension using components from a Can Am Spyder (three-wheeled motorcycle); we shortened the wishbones and used a modified steering rack from a small car. This approach was not entirely satisfactory—the turning circle was larger than necessary, and we could not get the ideal Ackermann angle. To avoid these compromises, we need to design and build our own.
Gentlemen, 10’s of thousand of hours by talented engineers have been spent on supension design and there is always a new approach to every challenge. Maybe contacting these engineers could quickly solve this issue and develop a new outside the box design.
Designing suspension was not a problem, though an experienced suspension engineer could undoubtedly have done it better and quicker. The difficulty was finding and adapting approved off-the-shelf components.
What capacity is the battery pack, and what cells does it use? Is it located in the front in the floor, and how far back does it extend? Were there any stability issues with two people and/or luggage; and have you ever run a double lane accident avoidance test? Here in the States this has to be done at 45+MPH.
I’m curious as to the range you get at a constant 88kph/55mph? Do you know an approximate kWh/km consumption? Do you have any defroster or heat in the Trev? What about passive air flow through the passenger compartment?
I’m currently building a 5 seat electric car I’m calling CarBEN EV5 that I hope will have a range of 300-400 miles, weigh under a ton, and have a Cd of <0.15. I using a moldless composite sandwich, and I cut 1" layers of XPS foam with a CNC machine. I did a 3D model in SketchUp, and sectioned it and then generated the g-code.
Trev’s original battery was 36 40 Ah lithium ion polymer cells, with a total energy of 5.5 kWh and a range of about 100 km. For Zero Race, we used 35 100 Ah lithium ion polymer cells, with a total energy of 13 kWh battery and a range of over 200 km.
The original battery was in the front compartment. The larger battery is in a tray beneath the floor, and extends from the nose of the car to about the front of the rear seat.
We have passed a lane change test at about 90 km/h, though that was with only one person in the car. Directional instability is noticeable at high speeds with a passenger; this could be improved by moving the rearmost cells back into the front compartment.
We drove from Darwin to Adelaide with one occupant (400 kg total mass) at about 80-90 km/h. The energy required to recharge Trev on this trip was 62 Wh/km.
We have a 12 V hair dryer pointing at the windscreen as a defroster. It is usually adequate with one person in the car, but does not clear the sides of the canopy (we have a cloth). We have an air intake on the front of the car, which we have to close when it is cold or wet; this needs to be improved. We are going to add small fans to blow air onto the driver and passenger for days when it is over 35 Celcius.
A range of 300-400 miles is going to require a big battery. Our polymer cells have a specific energy of about 150 Wh/kg. If you can achieve an energy consumption of 100 Wh/km (your vehicle is larger and heavier than Trev) then your battery mass will be over 300 kg.
Thank you for the details! It is great to have you folks with so much direct experience. The Trev is an amazingly efficient car, up there at the top with the Edison2 eVLC and the Bochum University SolarWorld GT.
Did you consider entering the X-Prize? I know they had a lot of rules, and requirements for cooling and heating and CANbus etc. discouraged a lot of folks from participating; people like Dave Cloud who has a car called Dolphin which has a 200+ mile range on a lead acid battery pack. It has 60 batteries, each weighing 33 pounds, and the total car weighs about 3200 pounds – the streamlining carries the day!
Have you considered an air exhaust vent on the back fascia say near the tail lights? This being a low pressure pocket of air could help pull air through the vehicle, and maybe avoid the need for a fan (at least as much).
You might also see a fair bit of improvement in Cd and consumption by using smooth flat covers on the front wheels. On typical (4 wheeled) cars, the spinning wheels and the wheel openings can contribute 20-30% of the overall drag; so in the Trev 10-15%? Tuft testing would show if this around the wheels and with improved flow toward the back. Aero drag is the key challenge once you settle on the most efficient drivetrain.
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