The Blue Sea Systems 3003 HD-Series Battery Switch Selector with Alternator Field Disconnect is rated 500A continuous and accepts 4/0 battery cables.
This is the selector version, choosing between two banks, where the 11003 is a straightforward On/Off isolator with the same rating. Both carry the alternator field disconnect, which breaks the field circuit before the main contacts open so the alternator is not switched off-load and its diodes survive.
The footprint fits common Perko and Guest low-amperage battery switch hole patterns, which makes an upgrade a straight swap on many boats. That avoids cutting a new opening in finished joinery, which is usually the hardest part of replacing a battery switch.
Tin-plated M12 copper studs give conductivity and corrosion resistance with extended length for multiple cable terminals. Tactile knob textures identify position by feel, it mounts surface or rear-panel, and it is ignition protected and meets ABYC battery switch requirements. Explore more battery switches.
- A selector, where the 11003 is On/Off isolation
- Both include alternator field disconnect
- Fits Perko and Guest hole patterns for a straight swap
- 500A continuous on 4/0 cable
