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PostPosted: Fri Jan 25, 2008 5:22 am 
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Joined: Tue Oct 28, 2003 2:52 pm
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Location: North Pole Alaska
After spending four years developing battery powered snowmobiles for the SAE Clean Snowmobile Challenge, the McGill University team decided to add a second vehicle to their program for 2007. Given the limited speed and range capabilities of the electric-only sled, they chose to follow the same path as General Motors and Ford did with their recent Volt and Airstream concepts and create a plug-in series hybrid snowmobile.

The new machine is an electrically driven unit like the previous one, but with the addition of an internal combustion range extender. The chassis comes from a Ski-Doo MXZ which is similar to the electric unit, but is designed for higher performance. The primary propulsion comes from a 35 kW motor made by Advanced AC. Electrical energy for the motor is stored in three lithium ion battery packs of twenty cells each with a total output of 72V. The three packs together have a capacity of 9.7kWh which can propel the sled about 30 miles.

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All this extra power and energy capacity has to have a cost and as usual with this type of system, that means weight. The new motor alone weighs in at 100lbs and the three lithium ion packs add another 240lbs. The combination of the larger base snowmobile and the hybrid drivetrain brought the total weight up to 850lbs, in line with the competing electric machines.

The payoff is dramatically improved range. Since a lot of recreational snowmobilers go a lot more than 30 miles at a time, the engine can raise that total range up to about 100 miles although as always, your mileage may vary. Warm March weather left the McGill team with only minimal testing opportunities and they didn't get the hybrid sled calibrated as well as they wanted. In spite of this, acceleration split the difference between the gas and electric machines.

Unfortunately the team also had to go back to mounting the batteries behind the seat on the hybrid machine making it prone to rolling during cornering. Those batteries and all the associated hardware are also expensive. The estimated cost of the hybrid came in over $20,000, a $15,000 premium over the stock unit. The team will be working diligently over the next year to improve the design and reduce the cost in time for the 2008 competition. In the meantime, the range extender has been temporarily moved from the sled to the Formula Hybrid racer the team will compete with at New Hampshire raceway next week.

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