Solectria Sunrise vs. Sunrise EV2 -- a Comparison

The Solectria Sunrise cost $100,000 because it was designed to be mass produced in high volumes, but was actually hand made in low volumes. It was optimized for efficiency, not performance; and built around donor car parts that are now over 20 years old. There were also aspects that were unfinished, to be optimized later if/when full production could be achieved.

The Sunrise EV2 design has therefore been updated and improved in a number of areas. Here are the differences between the original and our version.

Body:

• The original Sunrise body was a carbon fiber / E-glass composite that weighed just 250 lbs. It was produced in one piece by a very complex mold intended for mass production. Many aspects were optimized for light weight at the expense of practicality; for example plastic windows, ill-fitting doors, poor ventilation, non-replaceable bumpers, etc.
• The EV2 body has been simplified to allow production in lower volumes with simpler molds. Among the many improvements:
  • Converted to a hatchback, for improved trunk space and utility
  • Glass in all windows, for durability
  • Improved ventilation, for all-weather use
  • Real doors, with better weatherstripping, roll-down windows etc.
  • Larger wheel openings for bigger tires
  • Increased headroom
  • Minimization of hard-to-mold pockets for door hinges, headlight and taillight buckets, etc.
  • Separate replaceable bumpers

Battery Box:

• The original was 108"L x 14.5"W x 11"H. It ran from just behind the front wheels to just behind the rear wheels. This made access difficult, and limited battery size choices.
• The EV2 box is larger; 120"L x 15"W x 12"H. This allows a much larger range of standard batteries. It extends from the front bumper to just ahead of the rear differential. The batteries are in a tray that slides out the front, for fast easy servicing and maintenance. Multiple trays can be used; one for range, one for speed, or even a hybrid tray that's half batteries and half ICE generator.

Brakes:

• The original Sunrise had manual Geo Metro front disks, and Dodge Neon rear drum brakes. The mismatched front/rear setup provided mediocre braking. The AC drive system provided regenerative braking.
• The EV2 braking system comes from the donor car. Depending on the year and options chosen, it can be power assisted front disks, rear disks or drums, and with or without ABS. The vacuum pump doubles as an air compressor for adjusting air bag ride height and emergency tire inflating. Regenerative braking is not planned for the prototype (Minnesota is pretty flat), but is provided for if desired.

Motor:

• Solectria used an expensive custom air cooled AC induction motor and controller, rated at 50 KW. Though highly efficient, acceleration was weak and there were overheating problems.
• The Sunrise EV2 has a universal motor mounting plate that accepts virtually any motor. The prototype uses a Netgain WarP 9" series DC motor. Though this reduces efficiency 10%, the price is drastically lower and it provides several times more peak horsepower. The motor is mounted behind the rear wheels and directly coupled to the differential with a standard spider coupler with virtually no machining.

Transaxle:

• The original Sunrise used a Geo Metro transaxle to drive the front wheels. It was locked in 2nd gear, as the AC motor had a 13,000 RPM limit and was electrically reversed. Though light, it was not very strong. As the batteries were in the rear, you had the odd situation of a front wheel drive car that was tail-heavy -- not good for handling.
• The EV2 has been changed to rear wheel drive, more befitting a sports car. A Ford 8.8" differential from the donor car is used, with new gears for a 5.14:1 ratio. This is a very strong part, often used in drag racing. No transmission is needed, and the motor is electrically reversed. The differential is flipped 180 degrees so it is upside down with the drive shaft pointing rearward. Dry sump lubrication is used with lighter weight oil to improve efficiency.

Suspension:

• The original used 1994 Geo Metro front, and 1994 Dodge Neon rear suspension components. Though light, they were inadequate for the car's 2979 lbs GVWR; handling and braking were mediocre.
• The EV2 uses 1989-1997 Ford Thunderbird, Mercury Cougar, or Lincoln Mark 8 front and rear suspension components. These cars are "super coupes" with the excellent handling of luxury sports cars. Their 4800+ lbs GVWR can safely carry considerably more weight. They have the power disk brakes and power steering expected in a modern car. Everything attaches to easily removed bolt-in front and rear subframes. Air bags and adjustable shock absorbers are used to accomodate the large range of vehicle and battery pack weights possible.

Wheels and Tires:

• Original: 13" Geo Metro front and Dodge Neon rear. These are small tires considering the weight of the vehicle. The front/rear bolt circles were different, which made spare tires and matching rims difficult.
• EV2: 15" from Thunderbird/Cougar donor. Our prototype uses Goodyear Integrity 185/65R15 low rolling resistance tires from the 2004-07 Prius.