What is a Land Rover MHEV 48V DC-DC Converter?

Understanding the Heart of Your Land Rover's MHEV System: The DC-DC Converter

If you own a modern Land Rover with a Mild Hybrid (MHEV) engine, you have a sophisticated 48V electrical system working alongside the traditional 12V system. The crucial component that links these two worlds is the 48V to 12V DC-DC Converter. This guide explains what it is and why it's so important.

The Two Voltages in Your MHEV

Your MHEV Land Rover has:

• A 48V system that powers the Belt-integrated Starter Generator (BiSG). The BiSG acts as a powerful motor to assist the engine and as a generator to recharge a small 48V lithium-ion battery during braking.
• A 12V system that powers everything else: lights, infotainment, windows, and all the control modules. This system uses a conventional 12V battery.

Crucially, MHEV models do not have a traditional alternator to charge the 12V battery.

The Role of the DC-DC Converter

The DC-DC converter's job is simple but critical: it acts as the modern alternator. It takes the high-voltage power from the 48V system and ‘steps it down' to a lower voltage (~14V) to continuously charge the 12V battery and power the 12V electrical network while the vehicle is running.

How it Works

1. The 48V BiSG generates power and stores it in the 48V battery.
2. The DC-DC converter draws power from this 48V supply.
3. It converts the 48V DC power into ~14V DC power.
4. This ~14V power is fed directly to the 12V battery and other 12V systems, keeping them running and fully charged.

Without a functioning DC-DC converter, the 12V battery will not be charged, and the vehicle will quickly become inoperable. If you've been diagnosed with a faulty unit, find the genuine replacement part here.