OEX ACX3412 Battery Master Isolation Switch On/Off SPST (Contacts Rated 275A @ 12V)

OEX ACX3412 275A Heavy Duty Battery Master Isolation Switch 12V to 48V DC SPST Self-Cleaning Contact 10mm Stud Terminals

The OEX ACX3412 is a heavy duty battery master isolation switch rated at 275A and compatible with 12V through to 48V DC systems. With a two-position On/Off SPST configuration, two 10mm stud terminals, a built-in self-cleaning sliding contact mechanism and corrosion resistant black plastic housing, it is designed for the main battery disconnect on high-current 12V, 24V and 48V installations including lithium battery banks, large dual battery systems, inverter-based setups and high-draw commercial vehicle applications where the lighter ACX3409 (75A, 12V only) would be insufficient. Surface or recessed mount, 52mm hole for recessed installation. 68x74mm. Covered by a one year warranty.

Product overview

The ACX3412 steps up from the ACX3409 significantly from 75A at 12V only to 275A across 12V, 24V and 48V DC, and from 8mm to 10mm stud terminals for heavier gauge main battery cables. This makes it the correct choice for lithium battery bank isolation, large dual battery systems with high combined current draw, inverter-based installations requiring a main disconnect rated above 75A, and 24V or 48V commercial vehicle applications where the ACX3409's voltage range is insufficient.

The built-in self-cleaning sliding contact wipes the contact surface mechanically on each switch operation, removing oxidation and contaminant buildup that would otherwise increase contact resistance over time. This is particularly valuable in marine, dusty and infrequently operated installations. The key removal mechanism differs from the ACX3409 on the ACX3412, the key cannot be removed in either the On or Off switch positions. The key is removed by rotating it 45° counter-clockwise to a dedicated removal position, allowing normal day-to-day operation without the key being removable, while still providing a security option when needed. The removable rear cover and side panels allow wiring access from multiple directions.

Features and benefits

275A at 12V to 48V DC: High-current rating suited to lithium battery banks, large dual battery systems, inverter installations and 24V/48V commercial vehicle applications. Steps up significantly from the ACX3409 (75A, 12V only).

12V to 48V compatible: Covers 12V, 24V and 48V DC systems wider voltage range than the ACX3409.

Built-in self-cleaning sliding contact: Wipes the contact surface on every operation to maintain reliable connection quality and reduce contact resistance buildup over time. Particularly valuable in marine, dusty and infrequently operated installations.

2x 10mm stud terminals: Larger stud size than the ACX3409 (8mm) for heavier gauge main battery cables.

Corrosion resistant black plastic housing: Suited to underbonnet, marine and outdoor mounting environments.

Key removable at 45° counter-clockwise: Key cannot be removed in On or Off switch positions. Requires rotation to a dedicated removal position, allowing keyless daily operation with security when needed.

Surface or recessed mount: Recessed installation requires a 52mm panel hole. Surface mount available without a cutout.

Removable rear cover and side panels: Flexible wiring access from multiple directions.

68x74mm: Compact form factor for a 275A-rated switch.

One year warranty: Covered by a one year OEX warranty.

Technical specs

Goes well with

OEX ACX3057, Ring Crimp Terminal 10.5mm ID Blue, suits 10mm stud, pack of 100

OEX ACX3057BL, Ring Crimp Terminal 10.5mm ID Blue, suits 10mm stud, pack of 14

Frequently asked questions

What is a battery master isolation switch used for? A battery master isolation switch provides a single point of disconnect between the battery and the vehicle's electrical system. It is used for safe servicing preventing accidental starts and protecting against short circuits for extended storage to prevent battery drain, and as a security measure. At 275A and 12V to 48V, the ACX3412 is suited to high-current and higher-voltage systems where a standard 75A 12V switch would be inadequate.

How does the key mechanism work on this switch? Unlike the ACX3409 where the key is removable only in the Off position, the ACX3412 key cannot be removed in either the On or Off switch positions. The key is removed by rotating it 45° counter-clockwise to a dedicated removal position separate from On and Off. This allows the switch to be operated normally without the key being removable during everyday use, with the key available when needed to prevent unauthorised operation.

How does the ACX3412 differ from the ACX3409? The ACX3409 is rated at 75A at 12V with 8mm studs. The ACX3412 is rated at 275A across 12V to 48V with 10mm studs, suited to significantly higher-current applications and multi-voltage systems. The ACX3412 also features a self-cleaning contact mechanism, is physically larger and uses a different key removal mechanism. Select the ACX3409 for standard passenger vehicle battery isolation and the ACX3412 for high-current, higher-voltage or demanding installation environments.

What ring terminal size suits the 10mm studs? The 10mm studs accept ring terminals with a 10.5mm or larger ID hole. The OEX ACX3057 (10.5mm ID, blue, pack of 100) and ACX3057BL (pack of 14) are suitable options. For heavier gauge cable at 275A, ensure the ring terminal's cable range matches the wire size being used.

What does the self-cleaning contact mechanism do? The built-in self-cleaning sliding contact wipes the contact surface mechanically on each switch operation. This removes oxidation, dust and contaminant buildup that would otherwise increase contact resistance over time, maintaining reliable low-resistance switching throughout the switch's service life particularly beneficial in marine, dusty or infrequently operated installations.