Nylon Blue 2 Pole VSR Isolator Switch Voltage Sensitive Relay Dual Battery Isolator Switch for Marine Boat RV

The MT003-BL brings the same voltage sensitive relay design to a blue housing, giving installers a colour option that separates the dual-battery relay from other components on a crowded panel. Everything inside is unchanged: a 12V DC unit rated at 140A continuous with a 160A intermittent allowance, built to manage charge flow between a start battery and an auxiliary bank.

In daily use the relay closes as soon as charging voltage appears, letting both batteries share the charge, then opens again when the engine or charger stops. That automatic behaviour keeps the cranking battery in reserve while the fridge, lights or electronics run from the auxiliary side — no manual switch, no procedure to remember before leaving the dock.

The nylon housing keeps weight down and resists moisture, fuel splash and the steady vibration of an engine bay, so the relay can be mounted where the batteries actually live rather than in a protected cabinet far away.

• Colour-coded blue housing — easy to identify the dual-battery relay in a dense wiring panel.
• Automatic charge linking — the relay closes once charging voltage rises and both batteries share current.
• Automatic separation at rest — when charging stops, the contacts open to keep the start battery isolated.
• 140A continuous, 160A intermittent — covers typical charge and accessory loads with headroom for short surges.
• Nylon moulding — moisture, fuel-mist and vibration resistant without adding bulk.
• Two-pole layout — simple in-and-out positive routing with one shared ground.
• Service-free operation — no knob to turn, no contacts to clean, nothing to forget at the ramp.

Work out the cable route before cutting anything — the relay sits between the two positive feeds and shares one ground:

• Pick a rigid, dry mounting point near both batteries, away from exhaust heat, belts and moving linkages.
• Run a cable from the start battery positive to the main terminal, and from the auxiliary positive to the second terminal.
• Take the ground lead to a clean chassis or engine-block fixing and check that each lug seats firmly.
• Match cable gauge to the 140A continuous rating, and fit a fuse at the battery end of any long run.
• After wiring, verify terminal torque by hand and confirm the relay only closes once charging voltage is present.

• Boats — charge splitting between start and house banks on outboards, inboards and compact yachts; the blue housing reads clearly against a marine wiring panel.
• RVs and campers — leisure battery charging with the vehicle battery held back from fridge and lighting loads.
• Cars and 4x4s — dual-battery layouts feeding fridges, compressors, work lights and recovery equipment.
• Workshops and plant — auxiliary power on trailers, compressors and mobile equipment.

For installers building several vehicles, the colour difference doubles as a quick visual check that the right unit went into the right build.

• Minimum order — 1 piece, so single units and trial batches both work.
• Price — negotiable, quoted against quantity and packing requirements.
• Capacity — 500 pieces per week.
• Lead time — 5 to 7 days for standard orders.
• Payment — T/T or Western Union.
• Packing — carton, with reinforced export packing for long-haul consignments.
• Support — selection advice, pre-dispatch batch inspection and follow-up on field feedback.