The rate of adoption in North America will be growing steadily, according to Navigant’s report, with 29.0% of new vehicles sold in North America by 2018 having the feature. Some with this feature will be selected as options, the forecast notes, but adds that “this level of penetration will only be achieved because manufacturers choose to make the functionality a standard fitment on some of their popular models.”

Lead-acid batteries will lead in revenue for energy storage in SSVs, according to Navigant, with 99.1% of the $2.6 billion total in 2013. In 2022, the total SSV energy storage revenue will grow to $9.8 billion, by which time Li-ion batteries will hold 12.6% of the market.

To keep drivers happy with a stop-start vehicle’s (SSV’s) performance, the process must be seamless, and it must not have any measurable effect on performance. The latest systems are starting to adopt some of the features that were first developed for full hybrid vehicles, Navigant notes. The challenge is to get the most efficiency benefits from the smallest cost increment.

Restarting can be accomplished by beefing up a conventional starter motor, adding an electric motor in line with the engine, or replacing the alternator with a starter-generator. Greater efficiency comes from implementing regenerative braking energy capture, which changes the demand on the energy storage system. Some level of electric drive assist is also possible. A longer period with the engine off also changes the nature of ancillary systems that must be electrified.

OEMs must choose carefully the functionality to implement when designing a stop-start system. They must also ensure it is seamless and comfortable for their customers. Some early systems have attracted negative attention by not being smooth in operation. Consumers are keen to experience the benefit of better fuel economy, but they are not necessarily willing to change their driving styles or requirements. Expectations are not uniform across all regions. As with many new technology introductions, consumer education would be a worthwhile investment to help manage expectations.

—“Stop-Start Vehicles”

Stop-start systems will help to roll out other electrification features that will combine with engine downsizing and other enhancements to increase efficiency without large-scale adoption of full hybrid or plug-in electric capability, Navigant suggests.