Automotive Start-Stop Systems are Tough on SLI Batteries

Voluntary and mandated efforts to reduce CO2 emissions and improve fuel economy are resulting in more significant numbers of vehicles being equipped with start-stop engine systems. 

Start-stop engines automatically shut off when the vehicle is at idle and restart when the driver’s foot leaves the brake pedal saving fuel and reducing emissions. During this time, the energy needed to power a growing number of electrical loads is provided by the battery rather than the engine alternator. While this saves fuel and reduces emissions, batteries now must do even more:

• Deliver 30,000 starts annually vs. 700 a few short years ago
•  Deliver 500 million-watt seconds of energy vs. half that previously
•  Support micro-cycles as electrical loads run off of the battery instead of the engine

Unlike in the past when batteries were maintained in a fully charged state and charged over time, vehicle batteries today are constantly operated in a partial state of charge and must support rapid recharging between engine on-off periods. Therefore, it is not surprising that battery life expectancy has decreased as vehicles have evolved.