Energy storage has long been recognized as the most critical component of electric-vehicle technology, presenting the greatest engineering challenges, economic expense, and technical risk. Conventional lead-acid batteries are impractical for most vehicle applications because of their low energy density. Using lead-acid batteries, a large Class 8 truck would require about 15,000 kg. of batteries to achieve an operating range of just 150 miles. Lead-acid batteries also have other issues in heavy-duty vehicle applications, such as power drop-off as they become discharged, and greater chances of fires or explosions when used in large high-voltage strings. For these reasons, TransPower and others have studied and experimented with a wide variety of alternative vehicle energy storage technologies over the past decade, including nickel metal hydride (NiMH), nickel cadmium (NiCad), nickel sodium chloride (NiNaCl), and of course a variety of lithium-based chemistries.

Lithium battery pack built by TransPower team member ISE.

Lithium battery cells are TransPower's choice for our first generation electric drive system because they offer the highest energy densities of any mature battery technology, which greatly reduces the weight and cost of the energy storage system. To safely harness the immense amounts of energy contained in large packs of lithium batteries, integrated packs must contain wiring, sensors, and controls to monitor and regulate battery temperature, voltage, and other characteristics. A prptotype lithium pack built by TransPower team member ISE is shown at left. TransPower is working closely with leading battery pack integrators such as ISE and Quallion to develop large lithium battery packs optimized for Class 8 trucks. These energy stroage systems will emply modular designs so that the size of the battery pack can be tailored to vehicle power and operating range requirements.

A key aspect of TransPower's product offering is our "EnerLease" option, which provides lease financing for battery pack purchases. Under the EnerLease option, lease payments for the battery pack can be spread out for as much as ten years. In many cases, these payments can be comparable to vehicle fuel savings, making the net cost of using batteries equal to or less than the cost of owning a truck using diesel or compressed natural gas fuel.