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The tough Mac Plus keeps service battery in peak condition

Short trips or variable input can mean that the service battery is never properly charged, but by monitoring and compensating for voltage loss, the Mac Plus DC-DC charger ensures an optimal charge.

Mastervolt, the Dutch-based pioneer of off-grid power systems, is pleased to announce the launch of the new Mac Plus DC-DC charger, designed to ensure the quick and safe charging of a boat or RV’s service battery even in the most challenging conditions.

The service battery provides the energy to run all the supplementary systems, such as lights, entertainment systems, fans and inverters. However, whereas the engine start battery is usually located right beside the engine and receives priority when it comes to recharging, the service battery is often some distance away, at the end of a long cable run. This creates a voltage drop and means it is less likely to receive a full charge, especially on short trips. Smart alternators found on many fuel-efficient modern engines deliver a variable voltage rather than a fixed output, which exasperates the problem.

The Mastervolt engineers have risen to the challenge by developing the new Mac Plus, a DC-DC charger that constantly monitors the service battery and ensures it always receives an optimal charge. Even fully depleted batteries can be quickly revived.

The Mac Plus achieves this by using Mastervolt’s proven 3-step charging characteristic to compensate for voltage loss, and can be paralleled to obtain charging capacities well over 100 A. The unit is built to the same rugged standards as the rest of the Mastervolt range, and is suitable for all types of battery chemistry, including Lithium Ion.

There is no fan so the unit runs silently with plenty of built-in protection. This includes engine run detection to protect the starter battery, and voltage stabilisation to safeguard delicate equipment.

With heavy duty connections for easy installation, and a MasterBus data cable connection for intelligent system monitoring and automation, the Mac Plus will guarantee the optimal condition of your service battery, even on short trips, and greatly extend its working life.

Key features

  • Fast and safe charging during short trips.
  • Suitable for all types of battery chemistry, including Li-Ion.
  • Temperature compensation and voltage sensing for optimal charge.
  • Silent operation from fanless design.
  • Starter battery protected by engine run detection.
  • Capable of charging fully depleted batteries.
  • Adjustable current limits to meet Euro5/6 requirements.
  • Voltage stabilisation to protect delicate equipment.
  • Parallel operation to achieve charging capacities well over 100 A.
  • Heavy-duty connections.
  • E-mark certification for mobile applications.
  • MasterBus data connection for system integration and automation.
  • Dip switches for quick set up.


Technical specifications


12 / 12-50 (12 V 50 A)


24 / 12-50 (24 V 50 A)


12 / 24-30 (12 V 30 A)


24 / 24-30 (24 V 30 A)


255 x 165 x 66 mm (10.0 x 6.5 x 2.6 in)


1990 g (4,4 lb)


-20 °C till +60 °C > 40 °C derating

Protection degree:       


Battery type:

Flooded, AGM, Spiral, Li-ion, Traction

Charge characteristic:                       

Mastervolt 3-step algorithm

Output voltage:

10-15 VDC / 20-30 VDC model dependent

Max. output:

50 A (12 V-models), 30 A (24 V-models)


natural convection

Sensors: battery temperature, battery voltage, motorloop
Status indicator:

3 LEDs


CE, ECE R10 (E-mark)


DC short circuit, overload, over temperature, reversed polarity (fuse)


3 x M8 terminal, wire 10-50 mm2


6-pole screw connection, wire 0,75 - 1,5 mm2