Charging booster – effectively use electricity while driving
If you travel a lot, charging while driving plays a crucial role in your motorhome's power supply. This is where a charging booster comes in. It ensures that your leisure battery charges reliably, quickly, and completely – and all automatically as soon as the engine is running. In this article, we'll look at how a charging booster works, why it's practically indispensable in modern vehicles, and what you should consider when choosing and installing one.
Why a charging booster? Function & benefits.
As soon as the engine is running, the alternator generates electricity – ideally the perfect source to charge your vehicle's battery. However, in practice, this only works reliably in older vehicles. Modern vehicles meeting Euro 5 or Euro 6 emissions standards use intelligent alternator control , which frequently reduces the voltage or even shuts off the alternator completely to save fuel. This means your vehicle's battery doesn't receive enough voltage to be fully and efficiently charged.
A charging booster compensates for these fluctuations by raising the voltage to the appropriate level for the auxiliary battery, ensuring a constant and regulated charging voltage, and simultaneously guaranteeing that the starter and auxiliary batteries operate completely separately. This allows you to make optimal use of the available energy while driving – even if you stop frequently or only drive short distances.
Charging booster vs. isolation relay
Especially in older vehicles, you'll still find split-charge relays . These connect the starter and auxiliary batteries while driving, as soon as the alternator provides sufficient voltage. This is simple and inexpensive – but only works reliably if the alternator outputs a constant voltage. This is no longer the case with modern vehicles equipped with intelligent alternator control. In these vehicles, the auxiliary battery often remains incompletely charged.
👉 A charging booster is therefore indispensable for modern vehicles.
A split charge relay is only a sensible option for older vehicles without a regulated alternator and if you have an AGM battery installed. A battery charger is mandatory for lithium batteries.
Technical selection criteria
When choosing the right charging booster, it's crucial that it matches the output of your alternator – because a charging booster always uses the alternator as its power source , regardless of the vehicle type. It ensures that the vehicle battery receives the optimal charging voltage, even if modern alternators significantly reduce their voltage or temporarily shut off.
It is therefore crucial that the booster is compatible with the rated output of your alternator. As a rule of thumb, a charging booster should draw no more than one-third of the alternator's output. This ensures system stability and prevents the alternator from being overloaded.
👉 Example:
Alternator 90 A → Charging booster with 30 A makes sense
Alternator 150 A → Charging booster with 50 A makes sense
Installation instructions: Cables, fuses & cooling
Sufficient cable thickness is particularly important, because the higher the charging current, the thicker the cable needs to be. Cables that are too thin not only cause power loss but can also overheat dangerously. Appropriate fuse protection is equally essential. This ensures that no components are damaged in the event of a fault.
Since a charging booster generates heat during operation, it should always be installed in a well-ventilated location. Avoid enclosed boxes or hard-to-reach corners where heat could build up. An ideal spot is near the vehicle's battery, as this keeps cable runs short and prevents unnecessary energy loss.
Suitable boosters for various vehicle types
Recommendations vary depending on the vehicle type and battery system. Older vehicles without a smart alternator can sometimes still be operated with a split charge relay, but a charging booster – especially for lithium batteries – is mandatory. A charging booster is strongly recommended for Euro 5 vehicles, while it is practically indispensable for Euro 6 and Euro 6d vehicles. As a general rule: whenever a lithium battery is used, a charging booster must always be installed to ensure reliable and complete charging.
Conclusion & Outlook
A charging booster ensures that your vehicle's battery is reliably and efficiently charged while driving – independent of your vehicle's alternator control system. It makes your energy system more stable, safer, and more efficient. Whether you're planning short trips or long journeys, a charging booster ensures that your battery makes optimal use of your driving time.
In the next article, we'll delve deep into shore power supply and chargers – you'll learn how to charge your battery quickly, safely and easily at your campsite, and which components your setup really needs to be ready to go at any time.
