Charging via the Tow Vehicle (120A Anderson Plug)

Your Harvok® electric caravan is equipped with a 120A Anderson-style plug and 25mm² cable to allow high-capacity charging from your tow vehicle’s alternator. This setup supports reliable charging while driving and is designed for compatibility with most standard 12V vehicle systems.

System Overview

  • A DC-DC converter (Model BI124) is pre-installed in your caravan.
  • It supports up to 1200W / 100A @ 12V charging.
  • Power is only drawn based on what your vehicle alternator can provide; the converter does not force draw.
  • Charging begins automatically once ignition is detected and minimum voltage is met.

Required Tow Vehicle Setup

To enable safe and efficient charging, we recommend the following:

  1. Install a 120A Anderson plug at the rear of your tow vehicle.
  2. Use a 25mm² heavy-duty cable from the alternator to the Anderson plug.
  3. Add a relay to prevent the caravan from drawing power when the vehicle is off.
  4. Do not install an in-vehicle DC-DC charger — it may interfere with the caravan’s built-in unit.

Important Technical Configuration

To ensure proper operation of the built-in DC-DC charger:

  1. Ignition Wire Setup:
    • The #1 “IGN” wire from the DC-DC unit must connect to Pin #12 on the caravan’s 12-pin flat plug.
    • Tow vehicle wiring must send a true ignition signal to Pin #12, which activates the DC-DC charger when the engine is on.
  2. DIP Switch Configuration (inside DC-DC unit):
    • DIP #1: ON
    • DIP #2: OFF
    • DIP #3: ON (use OFF if vehicle has a standard alternator)
    • DIP #4: OFF
    • DIP #5: OFF
    • DIP #6: OFF
  3. Charging Voltage Detection:
    • If DIP #3 is ON (Smart Alternator mode), charging begins when the input voltage exceeds 11.6V.
    • If DIP #3 is OFF (Standard Alternator mode), charging begins when voltage exceeds 12.8V.
  4. Load Impact on Tow Vehicle:
    • Once charging starts, the DC-DC will step up and draw significant current, causing a voltage drop on the towing vehicle.
    • If the vehicle cannot maintain voltage, the DC-DC may behave erratically (clicking on/off repeatedly).
    • Ensure your alternator and wiring are sufficient to maintain stable supply during load.

Charging Behavior While Driving

  • When all conditions above are met, the DC-DC charger activates and steps up the voltage to charge the caravan’s battery bank.
  • Charging continues as long as:
    • Ignition is active
    • Minimum voltage is met
    • Anderson plug is properly connected

Troubleshooting Checklist

  • Is your tow vehicle engine running?
  • Is Pin #12 on the 12-pin plug connected to vehicle ignition?
  • Is the DIP switch set correctly?
  • Are cable size and Anderson plug rating correct?
  • Is your alternator capable of supporting sustained output?

Manual Reference