Glossary

Battery main switch

Unit A

What is Battery main switch?

A switch that disconnects a battery bank from the on-board system — for maintenance, longer lay-ups and emergencies. Every battery bank needs such a means of disconnection.

What matters about Battery main switch in practice?

It belongs in a place that can be reached without tools and without climbing, and is selected according to the system's continuous current — not the starter current, provided the starter has its own path.

Loads that must remain permanently supplied — bilge pump, alarm, gas detector — are deliberately connected before the main switch, but then with their own fuse. Internal contacts burn invisibly over the years: a warm main switch under load is a finding.

How large must a battery main switch be?

What matters is the continuous current flowing through the switch in use, for example from inverter, anchor windlass or bow thruster. On top comes the short-term rating for starting currents. Both values are in the data sheet and should be above the actual demand.

What kinds of switch are there?

  • On-off switches for a single battery or battery bank.
  • Selector switches with the positions 1, 2, both and off.
  • Remote-operated switches controlled by push buttons or the on-board control system.

What to watch when switching

Do not switch off while the alternator is running: if the battery suddenly disappears, the voltage spike can damage the regulator. The main fuse also belongs directly at the battery terminal; the switch does not replace it. The page battery main switch gives an overview of types and selection.

Related terms

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