Alternateur Alpha Compact 14/120 incl. Alpha Pro III

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Mastervolt

46614120

Alpha Compact 14/120 Alternator with Alpha Pro III

The Mastervolt Alpha Compact 14/120 alternator delivers a continuous charging current of 120 A at 12 V, with a capacity of 70 A even at idle (1800 rpm) for large-capacity battery banks, including Lithium-Ion. This compact model features dual internal ventilation and is controlled by the supplied external regulator, enabling full integration into the MasterBus network and a three-stage programmable charging algorithm.

Included with the product: Alpha Compact 14/120 alternator, Alpha Pro III charge regulator, and temperature sensor (drive pulley not included).

Retail priceBenefit from the professional rate

2.498,32€

2.498,32€ ~~2.859,60€~~

Tax included. Shipping calculated at checkout.

In stock

Free pickup point shipping over €150 in France
Pickup at Skysat possible

Custom installation

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Installers near you

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Support service

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Technical specifications

Series	Alpha Compact
Nominal voltage	12.0
Nominal current	120.0
Power	1.44
Max rotation speed	6000.0
Cut-in speed	1300 RPM
Idle current	70.0
Mounting style	Saddle mount
Rotation direction	Clockwise
Galvanic isolation	No
Field control type	N-type (negative command)
Housing temperature sensor support	Oui
Min pulley diameter	53.3
Max pulley diameter	71.1
Min pulley ratio	2.25
Max pulley ratio	3.0
Cooling method	Dual integrated fan
Cooling fan count	2.0
Max operating temperature	120.0
Température d'arrêt de charge	120.0
Weight	6.7
Marine-ready	Oui
Taille du terminal de sortie (mm)	M8

Detailed description

Alpha Compact 14/120 Alternator with Alpha Pro III Regulator

The Alpha Compact 14/120 Alternator by Mastervolt (reference 46614120) is a high-performance charging system designed for marine and mobile energy storage installations. Operating on a 12 V network (14 V charging voltage) with a 120 A output current, it is specifically optimized to deliver high power continuously, even at low engine speeds (idle). The unit weighs 6.7 kg and features an open construction with an integrated dual internal fan for optimal cooling, even in high ambient temperature environments.

Comparison with standard alternators and the Alpha range

Unlike OEM alternators installed by default by engine manufacturers, or Mastervolt’s standard Alpha range, the Alpha Compact series stands out with a 25 % smaller footprint and 40 % lighter weight. Its patented magnetic design reduces fuel consumption by 30 to 40 % compared to equivalent competitors. Designed to fit directly onto factory power take-off (PTO) mounts, it offers a superior alternative to basic alternators, capable of handling the intensive charging cycles required by modern service battery banks.

Technical specifications and wiring

This alternator features a clockwise rotation direction and is mounted using a swivel arm. It includes two M8 positive output studs, an isolated W (RPM) signal connection via Faston terminal, and a dedicated Mastervolt connector for excitation current. By default, the system is not galvanically isolated (negative pole connected to the housing), but isolated operation is possible by installing optional insulating sleeves. Cables and electronics are sealed against oil, moisture, and contaminants. Note that the multi-groove free-wheel pulley is not included, allowing selection of the exact diameter suited to the installation.

Advanced regulation with Alpha Pro III and MasterBus compatibility

The package includes the Alpha Pro III charge regulator (firmware 4.0 or higher), which transforms this alternator into a true three-stage (Bulk, Absorption, Float) smart charger. It is compatible with lead-acid, Gel, AGM, and Lithium-Ion battery banks. The charging process is temperature-compensated via an integrated probe (RJ12 connection) to prevent overcharging. The Alpha Pro III is fully connectable to the MasterBus network for real-time monitoring of RPM, charge state, and alarm configuration. It also features an engine load balancing function to reduce mechanical wear and a "Keep alive" function ensuring reliable signal transmission to the onboard tachometer.

Documentation

Type	Nom
	FR - Manuel d'installation et d'utilisation - Alternateur Alpha Compact 14/120 incl. Alpha Pro III
	EN - Manuel d'utilisation et d'installation - Alternateur Alpha Compact 14/120 incl. Alpha Pro III
	FR - Manuel d'installation et d'utilisation - Alternateur Alpha Compact 14/120 incl. Alpha Pro III
	EN - Manuel d'utilisation et d'installation - Alternateur Alpha Compact 14/120 incl. Alpha Pro III

Expert opinion

Pol CONIN

Digital Manager

« The benchmark for fast charging at low RPM with intelligent regulation MasterBus »

The Mastervolt Alpha Compact 14/120 alternator represents a strategic upgrade for vessels requiring rapid and reliable charging of large 12 V service banks. One of its key advantages is its ability to deliver 70 A even at idle speed, addressing the typical shortcomings of factory-fitted alternators. The inclusion of the Alpha Pro III regulator is decisive: by switching to a 3-stage charging algorithm with thermal compensation (-30 mV/°C), it maximizes the lifespan of AGM, Gel, or Lithium-ion banks. Native integration with the MasterBus network ensures perfect synergy with a MasterShunt, providing full visibility and secure management up to 120 °C in confined engine compartments.

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Alpha Compact 14/120 Alternator with Alpha Pro III

2.498,32€

2.498,32€ ~~2.859,60€~~

Frequently Asked Questions

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What is included with the Alpha Compact 14/120 alternator?

The alternator is supplied complete with the Alpha Pro III smart charge regulator, a battery temperature sensor, and the oil-resistant wiring harness required for installation.

What power output does this alternator deliver at idle?

This alternator is designed to deliver high performance even at low engine speeds. It provides 70 A of current at idle, with a maximum nominal capacity of 120 A at cruising speed.

Is this alternator compatible with lithium batteries?

Yes, thanks to the included Alpha Pro III regulator, this system is fully compatible with lithium-ion batteries, as well as classic technologies such as lead-acid, gel, and AGM.

What is the role of the Alpha Pro III regulator supplied with the alternator?

The Alpha Pro III regulator converts the standard alternator into a genuine 3-stage (Bulk, Absorption, Float) smart battery charger. It optimizes charging speed, protects batteries from overcharging, and compensates voltage based on temperature.

How does temperature compensation work on this model?

The system uses an included battery temperature probe to be mounted on your battery bank. The controller automatically adjusts the charging voltage with precise compensation of -30 mV/°C, protecting your batteries from overheating and extending their lifespan.

Can the Alpha Compact 14/120 alternator be connected to a MasterBus network?

Yes, the Alpha Pro III regulator has two RJ-45 ports that allow direct connection to the MasterBus CAN-bus network. This enables full monitoring and configuration from compatible helm displays.

What is the weight and dimensions of this alternator?

The Alpha Compact range has been specifically designed for the limited spaces of modern engines. This model features a compact footprint and weighs only 6.7 kg, making handling and installation significantly easier.

What is the maximum operating temperature of the alternator?

The Alpha Compact 14/120 alternator is designed to withstand confined and very hot marine environments. Its patented magnetic design allows it to support operating temperatures up to 120 °C without critical performance loss.

What are the default charging voltages applied by the charge controller?

For a 12 V battery bank, the charge controller applies a default voltage of 14.25 V for Bulk and Absorption phases, and 13.25 V for Float phase. These values are fully adjustable via the MasterBus network.

How to connect the tachometer (W signal) to this alternator?

The connection for the W signal, essential for the dashboard tachometer to function, is made very simply via a dedicated insulated quick-connect terminal directly on the alternator body.

Is it possible to mount this alternator in an isolated configuration from the ground?

Yes, if your installation requires an isolated ground mount (common on aluminum hulls), you can use insulating sleeves (available as an option) to insert on each side of the mounting holes to electrically isolate the alternator from the engine block.

What type of wiring should I use to connect the regulator to the alternator?

You must use the wiring loom supplied with the Alpha Pro III regulator. This specific cable is hydrocarbon-resistant and ensures a reliable connection for the excitation current and sensors.

What to do if the regulator alarm indicates an excessive field current?

If the LED flashes 3 times every 2 seconds, this indicates an overcurrent in the excitation circuit. The regulator stops charging for safety and retries every 5 seconds. Check the wiring between the regulator and the alternator for any short circuit.

How is the alternator cooled during operation?

The Alpha Compact alternator features a high-performance cooling system with a dual-fan design. This design allows it to maintain a high energy output even in poorly ventilated engine compartments.

Can this alternator be used on a 24 V battery bank?

No, the Alpha Compact 14/120 model is specifically wound and designed for 12 V battery banks. For a 24 V installation, you must choose a model from the Mastervolt 28/xx series (such as the 28/110 or 28/150).

What are the connection terminals for the power output?

The Alpha Compact 14/120 alternator is equipped with two robust M8-type positive output terminals. This allows for load distribution and ensures optimal and secure power transfer to your battery bank.

Can the Alpha Pro III regulator communicate with a MasterShunt?

Yes, via the MasterBus network, the regulator can communicate directly with a MasterShunt battery monitor. This allows the regulator to use the shunt's ultra-precise data (temperature and actual terminal voltage) to fine-tune the charging cycle as accurately as possible.

Should the temperature sensor be installed on lithium batteries?

No, lithium-ion batteries do not require external temperature compensation for charging. The temperature sensor is only required if you are charging battery banks of lead-acid, gel, or AGM types.

What happens if the alternator temperature becomes too high?

Thanks to the temperature sensor integrated into the Alpha Compact alternator, the regulator will automatically reduce the output power from 85 °C and will completely stop charging if the temperature reaches 120 °C, to protect the equipment autonomously.

How to configure the battery type on the Alpha Pro III charge controller?

Battery type configuration (lead-acid, gel, AGM or lithium) is performed easily via the MasterAdjust software or a compatible display using the MasterBus network. This allows perfect adaptation of charge algorithms to your bank specifications.