SLTF Marine LLC.
Technology Done Right


Columbia, MD 21045
410.799.3915

1-2-BOTH Battery Switch
On many older boats, the big 1-2-BOTH battery switch can be either a make-before-break switch or a break-before-make switch. Engineering speak! What it really means is a description of what happens when you turn the switch knob/handle/etc.:

Make-Before-Break

Nowadays, all switches are make-before-break., As you turn the handle from 1 to BOTH to 2, the battery voltage to the boat will never go to zero, i.e., there is never a voltage interruption. If you had a light on while turning the switch, you would see that it doesn't blink, though the light brightness might change, depending on your battery voltages. If this is your switch type, you can switch it while the engine is running.

Break-Before-Make

As you turn the handle from 1 to BOTH to 2, the battery voltage gets disconnected before each new switch position. If you had a light on while turning the switch, you would see it blink off then on. If this is your switch type, don't ever switch it while the engine is running or you could blow out your alternator!

Never switch off the battery switch with the engine running. Doing so will destroy your alternator!

 

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