ER2 electric race car on Pikes Peak 2002
Compact Power ER2 negotiates slippery hairpin curve on 12.5 mile race to top of Colorado's Pikes Peak. The car is powered by new lithium ion polymer batteries.

ER2 Conquers Pikes Peak

Interview with Compact Power's Dan Rivers and Tim Eckert

By Bill Moore

The first time Compact Power took a run at the 14,000 summit of Colorado's Pikes Peak in the summer of 2000 the mountain won. Powered by high-powered, but low energy-density lead-acid batteries, the car ran out of ‘juice' before it reached the end of the 12.5 mile winding dirt and gravel road that is one of America's most daunting automotive challenges.

Last summer the story was different. Equipped with a hastily assembled and installed set of lithium ion polymer cells from its partner, LG Chem, Ltd., in Korea, the new ER2 not only made it to the top but did so in record time for an electric vehicle. Of course, the purpose wasn't to beat the record set by a Honda EV Plus, but to demonstrate the ruggedness, durability and flexibility of Compact Power's new battery technology.

The story begins with GM's EV1, then known as the Impact, in the early 1990s. GM had claimed it could produce a modern electric car at the LA Auto Show in 1990, an off-handed comment that lead to the passage of California's Zero Emission Vehicle mandate a few months later. To prove its technical prowess, as well as to save face, General Motors assembled a team of engineers from GM, Aerovironment and Hughes Electronics to take the Impact from concept to a viable production vehicle. One of the members of the Hughes team was Dr. Dan Rivers, now the president of Compact Power, Inc. of Monument, Colorado.

As one of the program managers, Rivers was responsible for integration of the inductive charging system and inverter. It was an assignment and an experience he would look back on with fondness.

"I think it was the best program I ever did for Hughes. It was very exciting... a lot of fun and also very challenging," he commented to EV World, confiding that he enjoyed being able to drive some of the early prototype vehicles home after work on city streets and freeways.

"The main thing that I realized though was that we needed better batteries,' he noted, "and that's why I am in that part of the business now."

That experience eventually led him to form a partnership with Korea's L.G. Chem, Ltd. in the late 1990s, eventually incorporating as Compact Power in 2000. Rivers and his partner, Howard Song, approached L.G. Chem about helping them scale up their small, lithium ion cellular telephone batteries for use in hybrid and battery electric cars. After extended negotiations, LG Chem invested as majority owner in Compact Power, which currently has 17 employees.

River's explained that Compact Power's core responsibility is to take the individual lithium ion cells its larger partner provides and integrates them into larger, automotive size batteries, including incorporation of the battery management system. River's sees his initial market being 42-volt and fully hybrid-electric vehicle battery packs, the later of which currently depends heavily on D cell-sized NiMH batteries.

He stressed that because lithium ion batteries must be kept within strict voltage limits, the battery management system is critical to maintaining the health of the system, including state-of-charge and temperature. While all of the manufacturing of the battery components will continue to be done in Korea, Compact Power also is evaluating new cell materials.

According to Rivers, lithium ion polymer batteries differ from conventional lithium batteries in several important ways. Lithium ion batteries are also known as liquid lithium ion. Their core components are usually wound or folded into a metal container which maintains pressure on the electrodes to promote ion exchange. Polymer versions of the battery are laminated and don't require the metal sleeves. Instead they can be inserted into metal foil pouches, which makes them ideal for cellphone batteries.

The advantage of this approach is that the finished batteries can be significantly cheaper and thinner. "We make them... also like stacking battery plates in a battery," he stated. But most importantly, they are considerably more powerful than competing battery chemistries. Rivers said that the batteries used in the ER2 are rated for their specific energy at 95 watt hours per kilogram and 2,000 watts per kilogram for specific power."

River's explained the difference between the two metrics, specific power and specific energy. Hybrid electric vehicles that must accept and deliver high transient electrical energy loads either from regen braking or demands by the electric motor require a battery with high specific power. By contrast, a battery electric vehicle like the EV1 or Th!nk city, which are destined for street operation, need all the range they can get. That power comes from batteries with high specific energy.

Intuitively, one would think that the batteries in the ER2 would be designed for high specific energy, but the opposite is the case. Because the race up Pikes Peak is relatively short, just 12.5 miles, Rivers and Eckert decided to use high specific power batteries to get the maximum amount of energy to the wheels during the brief run up the mountain. What they discovered was that when all was said and done, they had more than enough power and maybe too much for the design of the car, a point Eckert explains in detail later in the interview.

To understand the difference modern lithium ion polymer batteries can make in hybrid, 42-volt, fuel cell and battery EV performance, Eckert noted that the ER1 equipped with conventional lead acid batteries only made it about three-quarters of the way up Pikes Peak using over 1,200 pounds of batteries. By contrast, the entire ER2 -- including its 245 pound lithium ion polymer battery pack -- weighs only about 1,200 pounds total.

According to Eckert, the biggest difference in the car is its power-to-weight ratio, which has dramatically improved the performance of the car. In addition to the Compact Power twin Compact Power battery packs that are placed outboard of the driver compartment, the Le Mans style racer utilizes a 165kW AC Propulsion drive motor and inverter.

As we'll see in Part Two of the interview next week, according to Eckert who drove the car, racing up Pikes Peak with that kind of power was like racing on a bed of marbles with no guard rails and 1000 foot drops.


Times Article Viewed: 8183
Published: 11-Jan-2003


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