Solar is great when the sun's out - but a DC-DC charger tops up your house battery every time you drive, so you arrive at camp with a fuller bank no matter the weather. It's one of the highest-value additions to an off-grid RV. Here's how it works and how to size one.
Shop DC-DC converters & battery-to-battery chargers.
What a DC-DC charger does
A DC-DC (or battery-to-battery) charger takes power from your tow vehicle's electrical system and delivers a proper multi-stage charge to your house battery - safely, at the right voltage for lithium. It isolates the house bank from the starter battery so you can't flatten the one that starts your vehicle.
Why modern vehicles need one
Many newer vehicles use smart/variable-voltage alternators that don't hold a steady charging voltage - so a simple relay won't properly charge a lithium house battery. A DC-DC charger fixes this by regulating the output regardless of what the alternator is doing.
Sizing a Victron Orion
DC-DC chargers are rated by output current - commonly 30A or 50A for campers. Match the charger to your alternator's spare capacity and your battery bank size: a 30A unit suits smaller banks, 50A recharges larger banks faster. Heavier draws may call for the isolated Orion models. Keep cable runs short and correctly fused.
Solar and DC-DC together
The two are complementary: solar charges while parked, DC-DC charges while driving. Running both is the most reliable way to stay topped up - see the full picture in how to build a Victron off-grid system.
Frequently asked questions
Do I still need solar if I have a DC-DC charger?
If you move most days, a DC-DC charger may cover a lot of your needs - but solar keeps you charged when parked for longer stays. Most off-grid rigs use both.
Will it drain my starter battery?
No - a DC-DC charger isolates the house bank and only draws when the engine is running (or per its configured settings).
Shop DC-DC chargers and the full Victron range. Ships from Upland, CA.