Start-Stop Batteries for Hybrid Electric Vehicles
After years of growth, the automotive market contracted after 2009, and manufacturers shifted focus towards the “green” segment of hybrid and pure electric vehicles. Mild hybrid vehicles with start-stop systems use conventional starter-lighting-ignition (SLI) batteries in a much more demanding way: they must accept charge quickly, deliver strong starting performance, and cycle frequently at high rates in a partial state of charge.
The battery challenge in mild hybrids
Conventional SLI batteries are not designed for this duty. Frequent cycling at a high-rate partial state of charge (HRPSoC) shortens their life, which is why hybrid programmes moved towards nickel-metal-hydride and other chemistries in early designs. Lead-acid manufacturers responded with improved battery designs.
How lead-acid adapted
Start-stop-specific lead-acid batteries – EFB and AGM – were developed to meet the cycling and charge-acceptance demands of mild hybrids. Carbon additives in the negative plate improve charge acceptance, and reinforced plate designs extend cycle life. These batteries deliver the cranking performance of an SLI battery with the cycling capability a start-stop system needs, at a cost that keeps the vehicle affordable.
Why it matters
Start-stop systems reduce fuel consumption and CO2 emissions by a meaningful margin, and the battery is the component that makes the strategy work reliably. Choosing the correct start-stop battery specification is essential for the system to perform across seasons and driving patterns.