Charging Systems


Euro 4 and earlier vehicles


The traditional way to charge a demountable camper or caravan  ‘service’ battery with older vehicles is via a Split Charge or Voltage Sensing Relay (VSR).

This method does work to a fashion, however it is very inefficient and the service battery rarely achieves 100% charge. In truth ‘fully charged’ with a typical Split Charge or VSR system is often only around 80% charged. When you consider the voltage drop caused by the long wire runs, undersized wire and dodgy connections, together with the differing types, sizes and needs of the starter and service batteries, a realistic expectation of anything better is really just pie in the sky.

In addition AGM and GEL batteries are extremely sensitive to over voltage so the  power spikes that take place whenever the service battery has been exhausted and the engine is started will damage them, dramatically shortening their lifespan. If you want to stick with this charging method a ‘Deep Cycle’ flooded lead acid battery is much better bet.

Fortunately the technology developed to cope with the needs of Euro 5 & 6 vehicles works just as well with older vehicles and simply by installing a Battery-to-Battery charger charging performance will be dramatically improved .

The Battery-to-Battery charger operates in the same way as a high end mains charger. The input voltage is irrelevant, just so long as the engine is running the service battery gets precisely the level of charge it needs. Multiple charging curves are incorporated so the charger can be optimised for flooded lead acid, GEL or AGM, and the special charging curves needed by Lithium batteries are usually included too (so if you want to upgrade to Lithium in the future you’ll be ready to go). With a typical Battery-to-Battery charger system the service battery will be FULLY charged around 5 times quicker than with the most efficient of VSR or Split Charge systems while at the same time significantly improving battery life.

Battery-to-Battery systems are integrated as standard into the onboard systems of many of our demountable and adventure campers and available as options on all others.


Euro 5/6 vehicles with ‘Smart’ Alternators/Regenerative braking


In order to reduce emissions and improve fuel economy Euro 5 & 6 vehicles are generally fitted with Smart alternators and a crude form of regenerative braking.

Driving the alternator takes power so the ECU essentially puts the alternator into idle when the vehicle is under load and seeks to compensate for this by working the alternator extremely hard when the vehicle is decelerating or braking. By harnessing the vehicle’s inertia to generate electrical energy, rather than petrol or diesel, fuel is saved and emissions reduced.

For this system to work the battery needs to be able to take very high charging loads so the batteries on these vehicles must always have some ‘headroom’ available for this charge. Generally this is achieved  by maintaining the starter batteries at around 80% charged.

Clearly with such a widely fluctuating alternator voltage, simply connecting our service battery to the vehicle battery in the normal way (VSR or Split Relay) is not going to be much help to us. Not only will the battery not be charging most of the time, GEL or AGM service batteries will be irreparably damaged by the very high voltages used by the smart/regen system when the system is charging.

The solution is simple and comes in the form of the Battery-to-Battery charger. As discussed earlier, the Battery-to-Battery charger operates in the same way as a high end mains charger. The input voltage is irrelevant, just so long as the engine is running the service battery gets precisely the level of charge it needs.

The vehicle’s Smart Charging and Regen systems are completely unaffected by the addition of the charger.

Battery-to-Battery systems are integrated as standard into the onboard systems of many of our demountable and adventure campers and available as options on all others.