DC-DC Charger
Also known as: B2B charger, battery-to-battery charger, split charge charger
A battery-to-battery (B2B) charger that takes power from the van's alternator while driving and charges the leisure battery at a controlled, correct voltage.
A DC-DC charger (also called a battery-to-battery or B2B charger) sits between the starter battery and the leisure battery. It steps the voltage to the proper multi-stage charge profile for your leisure battery's chemistry — essential for LiFePO4, which a raw alternator feed charges badly.
On modern Euro 5/6 vans the alternator is 'smart': it varies its output voltage and often drops it under load, so an old voltage-sensitive split charge relay barely charges at all. A DC-DC charger ignores that and pulls a steady current — Sterling Power's BB1230, for example, is a 12V 30A unit explicitly built for Euro 5/6 smart alternators and regenerative braking. Sizes are rated in amps (typically 18–50A); bigger charges faster but draws more from the alternator.
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