Glossary

Starter battery

What is Starter battery?

A battery that briefly delivers very high currents for the starter motor and is then immediately recharged. It is not built for cyclic use.

What matters about Starter battery in practice?

Its thin, large-area plates deliver a lot of current but tolerate few deep discharges. Connecting loads to it shortens its service life considerably.

The starter cable is the only circuit on board that is usually not fused — it is short, thick and carries currents in the hundreds of amps. Its ground belongs on a separate short path, not via the star point of the loads.

What matters in a starter battery?

The cold cranking current, i.e. the current the battery can briefly deliver in the cold, and a capacity that suits the engine. The engine manufacturer’s specifications are the basis for this.

How is the starter battery charged?

  • While driving, directly from the alternator.
  • On shore power via a charger with its own output for the starter battery.
  • Via a split charge relay or a DC-DC charger working in reverse, if the device supports it.

Are there lithium starter batteries?

Yes. LiFePO4 starter batteries are lighter and hold their voltage better during cranking. They need an alternator and regulation that suit the battery type, and a solution for winter if charging takes place in frost. More on charging from the engine on the page boat alternator.

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