Projecta 45A 3-Stage DCDC Charger

No, you do not need an external solar regulator if your DC-DC charger features a built in solar input. These units are designed to act as the primary charge controller for your auxiliary battery, with a built in MPPT or PWM regulator that manages the raw voltage coming directly from your solar panels.

Using a solar panel that already has its own regulator attached can actually reduce charging performance, as the two controllers will compete and potentially cause the system to shut down. To get the best results, you should connect "unregulated" panels directly to the dedicated solar input on the DC-DC unit. This allows the charger to properly manage the flow of power and maximize the energy harvested from the sun.

Check out our range of 12V Solar Panels to find compatible unregulated options, or browse our standalone Solar Controllers if you prefer a separate setup.

Sizing depends on the capacity and chemistry of your auxiliary battery bank. For a standard 100Ah AGM battery, a 20A to 25A charger is usually ideal for maintaining battery health.

If you have upgraded to a 200Ah Lithium setup, a 40A or 50A charger will provide faster recovery times without overstressing the cells. It is important not to go too large, as every battery has a maximum recommended charge current that should not be exceeded. Matching the charger output to your battery size helps achieve efficient charging from both your alternator and solar panels.

Always match the charger to your storage capacity. Explore our 12V Batteries collection or browse our high performance Lithium Batteries to find a suitable match.

Most modern DC-DC chargers can draw power from the alternator and solar panels at the same time. This process is often called solar blending or Green Power Priority, and it allows the unit to reach its maximum charge rate faster by combining both energy sources.

The charger typically prioritizes solar input to reduce the load on your vehicle alternator. If your panels are producing 10 amps and the charger is rated for 40 amps, the unit will draw the remaining 30 amps from the alternator. It is an efficient way to manage power while driving, especially if you have a larger battery bank that requires a high volume of energy for recovery.

Balancing these inputs is the key to running high draw appliances. Explore our 12V Pure Sinewave Inverters to see how to use that extra power, or check our Battery Monitors & Shunts for a clear view of your charging data.

Yes, your DCDC charger will continue to charge from the solar panels while the vehicle is parked and the engine is turned off. The unit is designed to switch over to the solar input as soon as the alternator stops providing power.

This keeps your auxiliary battery topped up throughout the day without draining your starter battery. Most chargers feature an isolation function that disconnects the vehicle battery once the ignition is off, allowing the solar regulator to focus entirely on maintaining your house battery for fridges and lighting. This functionality is what makes these units so effective for extended stays where you are not moving the vehicle for several days.

Explore our range of solar gear to find the right panel to pair with your charger.