OFF-1-BOTH-2 Marine Battery Selector Switch DC 32V Dual Battery Isolator with 1,200A Cranking Rating

A selector switch is really a small battery management system: three studs, four positions, and every decision about which bank feeds the boat. The MT081 handles that job at DC 32V with 350A continuous, 600A intermittent and a 1,200A cranking burst — sized for twin-bank 24V installations where the selector is also the master switch.

The dial order is marked OFF-1-BOTH-2. Putting OFF at the end of travel is deliberate: the position you need in a hurry is the one you reach by turning the dial all the way, not one you have to find in the middle of the scale.

1. OFF comes first — The dial begins at OFF in the clockwise order, so killing everything is a short counter-clockwise move rather than a hunt around the scale. For a boat that is left unattended for weeks, that is the position that matters most.
2. 1 — bank one only — The everyday running position on a twin-bank installation. Bank two stays isolated and fully charged for the day it is needed.
3. BOTH — paralleled — The two banks are joined to the common output. Useful for an emergency start or for letting a single alternator top up both banks while under way.
4. 2 — bank two only — The reserve position. If bank one has been flattened by a fridge left running, one move brings the electronics and the engine back.

• Bank 1 positive to the first stud — Crimp a closed ring lug, seat it flat, and torque it before moving to the next stud.
• Bank 2 positive to the second stud — Keep this cable the same cross-section as the first; unequal cable makes one bank work harder in BOTH.
• Common output to the starter or distribution panel — One cable carries everything the dial selects. Size it for the total continuous load, not for one bank.
• Fuse each bank at the battery end — The selector can break the circuit but it cannot protect the cable between battery and switch.
• Support the cables — Clamp each run within a short distance of the stud so vibration does not work the terminal nuts loose.

• With the dial in BOTH, a single alternator or charger feeds both banks at once. Convenient, and adequate on a small boat with matching lead-acid banks.
• Leave the dial in 1 or 2 when the boat is unattended. Paralleled banks equalise through the switch, so a weak cell in one bank will drag the other down.
• Do not pair a lithium bank with a lead-acid bank in BOTH. Their charge profiles differ and the switch cannot arbitrate between them.

MT081, OFF-1-BOTH-2 selector, DC 32V maximum, 350A continuous, 600A intermittent and 1,200A cranking. There is no minimum order quantity: single units, samples and mixed containers are all accepted, with pricing quoted against quantity and packing. Standard production takes 30 days from deposit, paid by T/T or Western Union with 30% down and the balance before shipment. Units ship in cartons; pallet lots quoted separately.