This guide explains the simplest and cleanest way to get 12V power on a 72V ONYX RCR: tapping into the existing headlight or tail light wiring. It starts basic and gradually goes deeper, so you can stop at the level you’re comfortable with.

Beginner: The short answer

Your ONYX already converts 72V from the battery down to 12V for the lights.

Two easy places to tap that 12V are:

  • The headlight harness (behind the headlight)
  • The tail / brake light harness (under the front of the seat, behind the battery)

Both provide switched 12V power that turns on and off with the bike.

Safety first (don’t skip this)

Before touching any wires:

  • Turn the bike on
  • Disconnect the battery
  • Wait a few seconds for the system to fully discharge

This prevents short circuits and protects the controller and DC converter.

Also:

  • Do not exceed 8A on a single 22 AWG copper wire
  • Use 18 AWG copper minimum

What wires to look for

At either the headlight or tail light harness you will find:

  • Yellow = +12V (positive)
  • Black = Ground (negative)

These two wires are all you need to power accessories like:

  • LED lighting
  • GPS trackers
  • USB chargers
  • Small amplifiers
  • Relays

Intermediate: how to tap the wires cleanly

Best practice is to use crimp connectors, not solder.

They:

  • Handle vibration better
  • Don’t become brittle
  • Maintain low resistance
  • Are easier to service later

Basic process:

  1. Cut the yellow and black wires
  2. Strip both ends
  3. Crimp your accessory’s positive wire together with the bike’s yellow wire
  4. Crimp the grounds together on the black wire
  5. Wrap with loom tape or heat shrink

That’s it. You now have a solid 12V tap.

Where exactly to find the harnesses

Tail / brake light harness

Location:

  • Behind the battery
  • Under the front of the seat

Pros:

  • Thick factory wiring
  • Hidden
  • Easy to route accessories under the seat

Headlight harness

Location:

  • Directly behind the headlight assembly

Pros:

  • Perfect for front-mounted accessories
  • Short wire runs
  • Easy access

Advanced: Understanding the stock 12V system

The ONYX RCR uses a built-in DC-DC converter that steps the main 72V battery down to 12V. While the unit is rated for up to 10A (≈110W), it is designed to operate reliably at about 85W continuous.

To stay within that safe continuous limit and leave headroom for the bike’s own electronics (display, controller logic, lights, etc.), you should plan on using no more than ~6A for added accessories.

Typical accessory power usage:

  • LED strips: 0.5-2A
  • USB charger: 1-3A
  • GPS tracker: <0.5A
  • Horn upgrade: 2-5A

If your accessory load begins to approach 7A or more, you should strongly consider upgrading to a 15A DC-DC converter to avoid overheating the stock unit and to ensure long-term reliability.

For higher-draw setups, also consider:

  • Adding an inline fuse
  • Using a relay for high-current devices
  • Or installing a higher-capacity DC-DC converter

Load & fire safety

If you add multiple devices:

  • Add an inline fuse
  • Make sure switches are rated for the current
  • Avoid thin wires for high-draw accessories

Overloaded wiring is the #1 cause of melted insulation and electrical fires on custom builds.

Optional: turn signal wire colors (for reference)

If you are also tapping turn signals:

  • Red = right signal
  • Purple = left signal

Front signals are near the headlight harness. Rear signals are in the tail light harness.

Quick checklist

  • Battery disconnected first
  • Yellow = +12V, Black = ground
  • Use crimps, not solder
  • Stay under 10A total draw (stock system)
  • Add fuses for high-load setups

If you stick to the headlight or tail light harness and respect the current limits, tapping 12V on the ONYX RCR is simple, safe, and fully reversible.