Perko Medium Duty Battery Disconnect Switch, Key Lock

The Perko Medium Duty Battery Disconnect Switch is rated 250A continuous and 360A intermittent, with an alternator field disconnect.

The alternator field disconnect is the feature worth understanding, and it protects the alternator rather than the battery. Switching a battery off while the alternator is charging strips its load instantly, and the resulting voltage spike destroys the diodes. The field disconnect breaks the field first so the alternator stops producing before the main contacts open.

That protection only works if the field circuit is actually wired to the switch. Fitting the switch without connecting the field terminal leaves the feature unused and the alternator exposed, which is a common omission on a rushed installation.

Ignition-protected construction supports installation in demanding onboard spaces, across 12, 24 and 32 volt systems. Two hundred and fifty amps continuous with 360 intermittent suits starting, house-bank and general marine power applications. Explore more battery switches.

• Field disconnect protects the alternator, not the battery
• Switching off under charge destroys the diodes
• It breaks the field before the main contacts
• Only works if the field terminal is wired