Lithium-ion batteries are helping to usher in a new era of transportation, allowing automakers to bring new hybrid-electric, plug-in hybrid-electric, and battery electric vehicles to market. Additionally, advancements in certain battery chemistries have enabled engineers to design and develop a number of other cutting-edge systems using lithium-ion technology beyond the electrified drivetrain.
While these next-generation applications boost fuel economy and enhance overall vehicle performance, they present unique engineering challenges—leveraging breakthroughs in battery technology for these applications requires a comprehensive understanding of vehicle electrical/electronic engineering and how various systems integrate.
For example, certain lithium-ion battery chemistries can be implemented in start-stop systems to replace existing lead acid designs. Automakers, especially in Europe, have embraced the concept of start-stop as a means of increasing fuel economy and reducing emissions. However, relying on a single lead acid battery limits the potential of start-stop capabilities—the expected life cycle of lead acid batteries will typically not support repetitive start-stop, and a single battery usually cannot sustain the voltage required to power the vehicle’s electronics while the engine is off. Some automakers are designing vehicles with two lead acid batteries, but this adds weight and decreases fuel efficiency, so it is proving to be an impractical solution.
Lithium-ion offers an attractive third option—depending on the chemistry, a single lithium-ion system can replace both lead acid batteries, providing cleaner, more reliable performance in a package that is about one-half of the weight. Lithium-ion systems also offer a far greater charge acceptance rate than lead acid, allowing the battery to capture more of the vehicle’s energy during deceleration/braking and store it to support electrical loads when the engine is off. This also reduces parasitic loss when the engine is on, further boosting fuel economy and increasing engine performance.
The engineering challenge, though, is how to integrate these advanced lithium-ion battery systems to maximize their full potential while ensuring compatibility with existing vehicle electronic design. With savvy systems engineering, communication and monitoring intelligence can be integrated directly into the lithium-ion battery pack, providing automakers with an advanced start-stop system that does not disrupt the normal operations of the vehicle’s electronics.
This start-stop function is just one example of how lithium-ion batteries can enhance existing automotive design. The key to unlocking the technology’s true potential is through a complete understanding of automotive systems engineering. A battery must respond quickly and consistently to power demands from any electronic component without impacting the performance of the other systems in the vehicle.
As automakers continue to face tremendous pressure to develop more fuel-efficient vehicles—both to comply with government regulations and to meet consumer demand for cleaner, more environmentally friendly cars and trucks—lithium-ion battery technology offers significant engineering advantages for improving existing systems.
In the near future, the value of lithium-ion will not be measured only in advanced cell design but also in complete systems that offer fully integrated electronics. Successful energy storage suppliers are currently investing the engineering resources necessary for understanding systems integration, so these next-generation solutions are rapidly progressing toward commercialization. Leading automakers are already starting to integrate lithium-ion replacements for lead acid batteries into their designs, signaling an immediate need for robust knowledge of electronics systems integration.
Glenn Denomme, Vice President of Engineering, A123 Systems, wrote this article in celebration of SAE's centennial.