3-Pin Anderson Plugs Explained: What They're For and How to Mount Them

Most people know the standard two-pin 50A Anderson-style plug. The three-pin version is newer and less familiar, but it solves a common wiring headache, especially when you're installing a DC-DC charger to run a second battery in a camper trailer or caravan. Here's what it does, what it connects to, and how to mount it properly.

What is a 3-pin Anderson plug?

A 3-pin Anderson-style connector is a single, one-piece housing with three contacts instead of two. It lets you run three conductors through one plug. A typical use is positive (from the alternator), negative (ground) and an ignition signal together, which is exactly what many DC-DC chargers need to know when the engine is running.

The 3-pin connectors VP Design sells are:

• fully insulated
• rated to 50 amps
• made from strong polycarbonate
• about 58 mm x 48 mm x 11 mm (plug size)

Will it connect to my existing Anderson plugs?

Yes, with one catch. A 3-pin Anderson-style plug can connect to another 3-pin plug and to standard 50A Anderson plugs. Colour still matters, though: grey connectors only mate with black and grey connectors. Check colours before you wire up a vehicle-to-trailer link.

Being able to mate with a standard 50A plug is handy. A trailer wired with an ordinary 50A plug can still connect to a vehicle fitted with a 3-pin socket for basic charging, while a trailer wired for 3-pin gets the ignition signal as well.

Why use 3-pin instead of two plugs?

• One connection instead of two. There's less to plug in at camp and less to forget.
• A neater install. One cut-out and one cover rather than a separate signal plug.
• Fewer mistakes. The ignition signal can't be left unplugged while the main power is connected.

Mounting options

The 3-Pin 50A Anderson Style Connector with Cover comes in a wide range of layouts:

• Flush mount panel with no plug, one plug or two plugs. The flush mount measures 110 mm x 49 mm x 40 mm and needs a 66 mm x 25 mm cut-out. Stainless hardware and lock nuts are included.
• Wall-mounted sloped mount (92 mm x 22 mm x 102 mm), with or without a plug. The slope helps shed water and makes plugging in easier.
• Combination mounts pairing a 3-pin Anderson with a 7-pin or 12-pin trailer plug, or with standard 50A plugs. These are useful on a tow bar or rear bar where both trailer lighting and charging connect.
• Bumper mount option.

Related products:

• 3-pin 50A Anderson plugs (replacement connectors)
• 7-pin trailer plug mount with Anderson plugs (includes a 3-pin option)
• Ford Ranger PX2/PX3 Anderson plug tub mount (3-pin option available)
• 175A Anderson flush mount panel (3-pin version for 175A connectors)

Wiring tips

1. Plan your pin-out and write it down. Use the same layout on the vehicle and trailer ends.
2. Size your cable for the current and run length. Undersized cable is the usual reason a DC-DC charger underperforms.
3. Strip about 1 cm of insulation from each core, then crimp the terminal lugs firmly with a proper crimping tool. A tug test should show they can't be pulled off.
4. Seat the terminals fully in the housing until they click home.
5. Fuse the positive close to the battery, following your charger's instructions.
6. Fit a cover or dust cap to keep the contacts clean on dusty roads.

If you're not confident with high-current wiring, have an auto electrician do the install. Your mount and plug choice will still make their job quicker and neater.

Made for touring

VP Design's 3D-printed mounts are printed in PETG and made in Victoria, Australia. The plugs themselves are polycarbonate connectors. Delivery is 3-18 days Australia-wide, with 30-day free returns.

See the full Anderson plug range, or read our Anderson plug cover and flush mount size guide.