Blue Sea Systems e-Series Selector 4 Position Battery Switch

The Blue Sea Systems e-Series Selector Battery Switch lets you isolate two battery banks to separate loads, or combine them into one for charging and emergency starts, all from a single 4-position knob. A make-before-break contact design means switching between banks never interrupts power to whatever's running.

Key features

• 4 positions: Off, Battery 1, Battery 2, Battery 1+2 Combine
• 325A continuous, 600A intermittent (5 min), 1200A cranking (30 sec)
• 32V DC maximum, 3/8"-16 (M10) tin-plated copper studs
• Ignition protected, IP66 rated, fits most Perko and Guest hole patterns

This is the standard 4-position selector without Alternator Field Disconnect. If the switch could ever be turned to Off while the engine is running, an AFD-equipped switch protects the alternator's diodes from damage in that scenario — Blue Sea's PN 9002e is the identical switch with that feature added, at a modest price difference.

Torque the terminal studs to 140 in-lb. This switch accepts up to 4/0 AWG cable, and its make-before-break design means it's safe to switch banks under load without a momentary loss of power to connected electronics. An optional ICON label kit (PN 7902) is available for customized position labeling.

This is a common upgrade for boats moving from a simple on-off disconnect to real battery-bank management — separating a start battery from a house bank day to day, while still having the combine position on hand for an emergency start if the house bank runs down. Mount it somewhere visible and reachable at the helm or engine compartment so its position is easy to confirm at a glance.