For decades automotive OEMs have invested time and money into vehicle electrification with the ultimate goal of improving fuel economy and emissions of their vehicle fleets. One ironic fact about vehicle electrification is that the high voltage batteries required to accomplish this increase the overall weight of the vehicle. This weight increase works against the efficiency of the electrification and performance of the vehicles.
To give an example, the BMW 5 Series Sedan 530i is 3770 lbs with a 6 cylinder engine, while the BMW Active Hybrid 5 is 4244 lbs with the same body style and engine. This 474 lb increase reduces the performance of the vehicle, although the hybrid is 40% more fuel efficient on urban drive cycles. The weight challenge is even more magnified on fully electric vehicles. The Ford Focus SE sedan powered by a 2.0-liter Ti-VCT I-4 engine is 2935 lbs. The Ford Focus Electric is 3624 lbs, 689 lbs more weight to haul down the road.
A newer trend in the automotive industry is a less aggressive form of electrification called the micro-hybrid. A micro-hybrid enables the vehicle’s internal combustion engine to stop running when the vehicle is stationary, such as at a traffic light, saving fuel by up to 10% above conventional vehicles. When the driver releases the brake to press on the gas pedal, the engine quickly starts again before the vehicle moves forward. This system requires a more robust 12V battery than those on today’s vehicles since it must restart the engine over and over at each stopping point, and it must support the electronic loads of the vehicle while the engine is off at a stoplight. A more durable 12V lithium-ion battery can replace today’s lead-acid batteries with the side benefit of a weight reduction as well. This replacement can result in a 28 pound (12.5kg) weight save on full size models. According to the EPA, a consumer can improve miles per gallon usage by up to 2% for every 100lbs of weight removed from a vehicle. This results in an additional 0.6% fuel economy improvement from the weight savings alone using the less massive lithium-ion battery.
Many OEMs have caught on to the weight savings benefit of 12V lithium ion starting batteries, especially in the super car and luxury markets. The 12V lithium-ion starter battery offered by A123 Systems is the only form of electrification available today at a net weight save. As automakers are under more pressure to find fuel saving technologies and micro-hybridization becomes more mainstream, 12V lithium-ion batteries will be a solution which contributes to both fuel efficiency and weight reduction.
