Charging while driving

Charging your leisure battery while you drive is one of the easiest ways to make better use of your time on the road. It tops up your power supply as you travel, lets you run appliances like fridges, fans or pumps without dipping into your stored energy, and helps keep your battery healthier for longer. Your engine is already doing the work, so it makes sense to put it to good use.

There are two main ways to do this, and the right choice depends on your vehicle and what you are hoping to get out of it.

Two ways to charge while driving

DC-DC Charger (Battery-to-Battery)

The modern, all-in-one solution. A DC-DC charger regulates and boosts the alternator's output to deliver a controlled, multi-stage charge suited to your battery, whether that is lead-acid, AGM, gel or lithium. It handles the variable voltages from smart alternators and stop-start systems, making it the most versatile and future-proof choice for any vehicle.

Key benefits:

• Works with all vehicle types including modern smart alternators
• Compatible with all battery types including lithium
• Delivers a controlled multi-stage charge — bulk, absorption, and float
• Only activates when the engine is running — never drains the starter battery
• Future-proof — any battery upgrade you make is already covered

Split charge relay

A simpler, more traditional option that links your starter and leisure batteries while the engine runs. It does not regulate or boost voltage, so it suits older vehicles built before 2015 with standard alternators and wet lead-acid batteries. It is not suitable for lithium batteries, and it is not reliable on modern vehicles with smart alternators.

If you are not sure which to go for, a DC-DC charger is the stronger choice for most setups.

How a DC-DC charger works

A DC-DC charger sits between your starter and leisure batteries, taking power from the alternator and converting it into a safe, correct charge for your leisure battery. It delivers power using the same multi-stage charging process as a mains charger:

• Bulk: charges at maximum current up to around 80% capacity
• Absorption: slows the charge to bring the battery to full without stressing the cells
• Float: drops to a low maintenance voltage to keep the battery topped up without overcharging

It monitors your starter battery's voltage and only switches on once the engine is running, so it never draws power while you are parked. Because it cuts off the moment you stop driving, you are always left with enough power to start your vehicle.

For most drivers, a DC-DC charger is the better long-term choice. It charges reliably on the move, works with any vehicle and battery type, and any upgrades you make down the line are already covered.