DC/DC Chargers

It charges your auxiliary (second) battery from the vehicle while you drive, delivering a proper multi-stage charge rather than just connecting the two batteries together. You'll want one for any dual-battery or deep-cycle setup — and it's effectively essential on vehicles with a smart or variable-voltage alternator, or if you're running a lithium auxiliary battery, where a basic relay simply won't get the battery to a full charge.

A VSR just links the two batteries together when the engine is running. That was fine on older vehicles, but modern smart alternators vary their voltage to save fuel and often don't push out enough to fully charge an auxiliary battery through a relay. A VSR also can't multi-stage charge or safely handle a lithium battery. A DC-DC charger boosts and regulates the voltage to deliver a complete, correct charge regardless of what the alternator is doing.

As a rough rule, aim for around 15–20% of your auxiliary battery's capacity in amp-hours. A 25A charger suits roughly a 100–200Ah battery, which covers most touring and camping setups; a larger battery bank, or a faster recharge, calls for more amps. Tell us your battery capacity and how you use it and we'll point you to the right size.

Yes — many DC-DC chargers have a dual input with a built-in MPPT solar regulator, so your alternator and solar panels can both feed the auxiliary battery, drawing from whichever is available. That's ideal for touring and off-grid use, where you charge on the move and top up from solar while you're parked up. If solar is part of your plan, choose a model with the solar input built in rather than adding a separate regulator.

Yes, as long as you choose a charger with a lithium charge profile — most current models let you select the battery type (AGM, gel, calcium, lithium and so on). Setting the correct profile matters, because lithium needs a different charge curve to lead-acid batteries. If you're running or planning a lithium setup, let us know and we'll make sure the charger suits it.

It mounts as close to the auxiliary battery as practical, with correctly sized cable for the run and current, fused at both ends, and an ignition or trigger wire so it only charges when the engine is running. It's a manageable install if you're confident with cable sizing, fusing and earthing, but there's more to it than a basic relay — if you're not sure, it's worth having an auto electrician wire it so it's safe and reliable.

As close to the auxiliary battery as you can, to keep cable runs short and charging efficient. Pick a spot that's dry, secure and ventilated, away from direct engine heat, since these units can get warm under load. Keeping it near the battery it's charging also makes the wiring simpler and helps the charger reach the battery's target voltage accurately.