Campervan DC-DC Chargers

A DC-DC charger is a battery-to-battery charger that takes power from your vehicle's starter battery and alternator and converts it into the correct charging voltage for your leisure battery.

Unlike traditional split charge relays, DC-DC chargers actively regulate the charging process, delivering a multi-stage charging profile designed to maximise battery performance and lifespan.

In simple terms:

Alternator → DC-DC Charger → Leisure Battery

The charger monitors voltage and safely controls the charging current, ensuring your leisure battery receives the optimal charge while you drive.

Modern vehicles often use smart alternators that reduce charging voltage to improve fuel efficiency and lower emissions.

While this benefits the vehicle, it can make charging a leisure battery difficult when using older split charge systems.

A DC-DC charger solves this problem by:

• Boosting charging voltage when required
  
• Providing a dedicated charging profile
  
• Protecting both batteries
  
• Maximising charging efficiency
  
• Ensuring compatibility with smart alternators
  

For many modern campervans, a DC-DC charger is considered essential.

The correct size depends on your battery capacity, charging requirements and electrical system design.

Most campervan installations use either a 30A or 50A charger.

Put simply, the bigger the amp (A) rating, the faster your leisure battery can be recharged from your vehicle's alternator. However, the charger should always be correctly matched to your battery bank and electrical system.

Both DC-DC chargers and split charge relays allow your leisure battery to charge while driving, but they work in very different ways.

A split charge relay simply connects your starter battery and leisure battery together when the engine is running. This allows the alternator to charge both batteries at the same time. While this method is cheap and simple, it relies entirely on the alternator's output voltage and offers very little control over the charging process.

A DC-DC charger takes power from the vehicle's electrical system and actively converts it into the correct charging voltage and current for your leisure battery. This ensures the battery receives a proper multi-stage charge, improving charging performance and battery lifespan.

How A Split Charge Relay Works

When the engine starts, the relay detects charging voltage from the alternator and closes the circuit between the starter battery and leisure battery.

This means:

• Both batteries are connected together
  
• The alternator attempts to charge both batteries
  
• Charging voltage is not regulated
  
• Charging performance depends entirely on the vehicle's alternator
  

While this worked well in many older campervans, modern vehicles often use smart alternators that reduce voltage during normal driving conditions. This can prevent the leisure battery from charging fully.

Why DC-DC Chargers Are Better For Modern Campervans

Smart alternators often lower their charging voltage after the starter battery is recharged. While this benefits the vehicle, it can leave a leisure battery partially charged when using a traditional split charge relay.

A DC-DC charger compensates for these voltage changes and continues charging effectively throughout the journey.

Yes. Most modern DC-DC chargers offer dedicated lithium charging profiles and are specifically designed for LiFePO₄ battery systems.

Yes. Many campervan electrical systems combine solar charging and alternator charging for maximum off-grid capability.
We sell a selection of combined DC-DC chargers with built in MPPT solar control chargers.

For most modern campervans, particularly those with smart alternators or lithium batteries, a DC-DC charger is highly recommended.