Alternateur Alpha Compact 28/150, régulateur Alpha Pro III inclus

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Mastervolt

46628150

Alpha Compact 28/150 alternator, Alpha Pro III regulator included

The Mastervolt Alpha Compact 28/150 alternator (24 V / 150 A), from the current high-performance range, delivers optimal charging current even at low RPM for demanding battery banks, including lithium-ion. Its control via the Alpha Pro III regulator ensures a three-stage charging cycle and native integration into the MasterBus monitoring network.

Includes: Alpha Compact 28/150 alternator, Alpha Pro III charge regulator, battery temperature sensor (supplied without pulley).

Retail priceBenefit from the professional rate

2.746,32€

2.746,32€ ~~3.130,80€~~

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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	24.0
Nominal current	150.0
Power	4.2
Max rotation speed	16000.0
Cut-in speed	1700 RPM
Idle current	28.0
Mounting style	Tiller pilot arm
Rotation direction	Clockwise
Galvanic isolation	Non-insulated
Field control type	Negative (N-type)
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 fans
Cooling fan count	2.0
Max operating temperature	120.0
Température d'arrêt de charge	130.0
Weight	7.9
Marine-ready	Oui
Taille du terminal de sortie (mm)	M8

Detailed description

The Mastervolt Alpha Compact 28/150 alternator (part number 46628150) is a high-capacity 24 V charging system designed for marine and industrial electrical installations. Supplied without a pulley, this model uses a specific magnetic design that reduces its volume by 25 % and its weight by 40 % compared to conventional alternators. It is provided with the external Alpha Pro III charge regulator to ensure precise control of the charging cycle for all types of battery banks.

Electromechanical and thermal performance

This model delivers a nominal current of 150 A at 6000 rpm (at 25 °C) and guarantees a production of 28 A at idle engine speed of 1800 rpm. The starting rotation speed is set at 1700 rpm, with a maximum tolerance of 16000 rpm. The mechanical power required on the power take-off (PTO) is 8.4 kW (11.4 hp). Cooled by a double internal fan within an open structure, the alternator supports an operating temperature of up to 120 °C. An integrated temperature probe with RJ12 connection ensures active thermal regulation. The electrical connections include two M8 positive output terminals, an isolated W-signal connection for the tachometer, and a proprietary Mastervolt connector for the excitation current. The net weight of the alternator is 7.9 kg, with a total packaged weight of 11.4 kg.

Alpha Pro III regulation and MasterBus integration

The Alpha Pro III regulator controls the output voltage via a three-stage charging algorithm (Bulk, Absorption, Float). This device compensates for temperature and optimizes charging for lead-acid, Gel, AGM, and lithium-ion batteries. The absorption phase is automatically timed (approximately 30 minutes for lithium-ion technology) before switching to float voltage. This regulator natively integrates the MasterBus communication protocol, enabling configuration of voltage thresholds, real-time charge data monitoring, and alarm management directly from the onboard network.

Positioning within the range and comparison

Within the Mastervolt catalog, the Alpha Compact series stands out from the standard Alpha range with an optimized power-to-size ratio and an estimated 30 % reduction in fuel consumption. Compared to competing equipment such as the 24 V Balmar XT series, the Mastervolt Alpha Compact 28/150 offers the advantage of direct software integration thanks to the regulator's native MasterBus network, eliminating the need for additional data conversion gateways. Its lightweight design is specifically intended for cramped engine compartments requiring high continuous charging power, where a traditional 150 A alternator would be too heavy or bulky.

Expert opinion

Pol CONIN

Digital Manager

« Compact power and intelligent MasterBus regulation for 24V systems »

The Mastervolt Alpha Compact 28/150 alternator represents a major evolution for embedded power architectures requiring high charging capacity under 24V. Delivering a nominal current of 150 amperes, its true operational advantage lies in its ability to provide very high power even at low RPM or idle speed, a critical requirement for modern marine applications. Thanks to a patented magnetic design, it is up to 40% lighter (7.9 kg net for the alternator alone) and 25% more compact than a conventional model of equivalent power. Its reduced footprint greatly facilitates integration as a secondary alternator (PTO). Note that this specific reference (46628150) is supplied without a pulley, allowing the installer to select the multi-groove interface that exactly matches the marine engine belt.

The strategic value of this system lies in the included Alpha Pro III regulator, which transforms this power block into a true 3-stage+ smart charger (Bulk, Absorption, Float). In practice, this regulator makes all the difference: paired with the supplied temperature probe, it dynamically adjusts voltage to protect battery banks from overheating and optimize charging cycles. Fully configurable and natively compatible with the MasterBus protocol, it integrates seamlessly into onboard networks and manages high-acceptance chemistry types with remarkable efficiency, particularly Lithium-Ion (Li-ion), AGM, or Gel. By pairing it with a MasterShunt on the network, centralized monitoring and surgical-precision energy management are guaranteed.

Designed for the harsh conditions of engine rooms, the Alpha Compact features internal electronics and heavy-duty wiring heavily protected against oil, moisture, and dirt. Cooling is provided by a dual internal fan, supported by active thermal protection that modulates performance to preserve equipment in high ambient temperature environments. This alternator-regulator pair is the solution of choice for yachts and professional vessels requiring maximum electrical autonomy and ultra-fast charging. It delivers OEM-level reliability while optimizing mechanical efficiency, enabling up to a 30% reduction in fuel consumption related to power generation.

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Alpha Compact 28/150 alternator, Alpha Pro III regulator included

2.746,32€

2.746,32€ ~~3.130,80€~~

Frequently Asked Questions

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What is included in the box when purchasing this alternator?

The packaging includes:

The Alpha Compact 28/150 alternator (delivered without pulley)The Alpha Pro III smart charge regulatorAn oil-resistant cable harness (1.5 m)A battery temperature sensor

What is the charging power of the Alpha Compact 28/150 alternator?

This high-performance alternator delivers a nominal current of 150 A at 24V (at 6000 rpm), corresponding to an electrical power output of 3.6 kW (with a required mechanical power of 8.4 kW). It can provide 28 A as early as 1800 rpm.

Is this alternator compatible with lithium batteries?

Yes, it is. Thanks to the included Alpha Pro III regulator, charging is perfectly suited to all battery types, including lithium-ion batteries, as well as flooded lead-acid, Gel, and AGM models.

Is the alternator supplied with its mounting pulley?

No, this alternator is supplied without a pulley. The pulley must be selected based on your engine’s specifications (power output, crankshaft pulley diameter, and desired reduction ratio).

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

The Alpha Pro III regulator converts the alternator into a smart charger. It provides a 3-stage+ charge (Bulk, Absorption, Float), compensates voltage based on battery temperature, and protects the system by reducing power in case of overheating.

How is the alternator protected against extreme temperatures in the engine compartment?

Unlike standard models, the Alpha Compact series is equipped with a highly efficient dual internal fan. This allows it to maintain optimal performance with an operating temperature up to 120 °C.

What is the maximum tolerated rotational speed for this model?

The alternator requires a starting speed of 1700 RPM to begin charging, and it can withstand a maximum rotational speed of up to 16,000 RPM.

Can I integrate this alternator into my existing MasterBus network?

Yes, the Alpha Pro III regulator is natively compatible with the MasterBus network. It features two RJ-45 data ports, enabling seamless communication with other components in your electrical installation.

What is the weight of the Alpha Compact alternator?

The alternator stands out for its exceptional power-to-weight ratio, weighing only 7.9 kg.

How does the system react in case of alternator overheating?

The regulator continuously monitors temperature. If the alternator reaches 85 °C, the regulator linearly reduces charging power. If the temperature climbs to 120 °C, it cuts off charging completely to prevent any damage.

Should I install a temperature sensor on my batteries?

Yes, for lead-acid batteries (Gel, AGM, flooded), it is strongly recommended to install the included temperature sensor. It adjusts the charging voltage and prevents thermal overload. Note that this sensor is not required for lithium-ion batteries.

Can I use this model to charge a 12V battery bank?

No, the Alpha Compact 28/150 model is exclusively designed for 24V DC service battery banks. For a 12V system, choose a model from the 14V range.

What type of mechanical mounting is used on this alternator?

This specific model is designed for mounting on a gimbal arm, which is a very common standard on many marine engines.

Does the Alpha Compact 28/150 alternator have galvanic isolation?

By default, this model is not galvanically isolated. However, if your installation requires an isolated setup (for example on an aluminium hull), insulating sleeves (optional kit) can be used during mounting.

What are the direct connections on the alternator?

The alternator is equipped with:

Two M8 positive output terminalsA connection for the W signal (tachometer)A Mastervolt plug for the field currentAn RJ12 port to connect the temperature probe

Is it possible to connect the regulator to a MasterShunt?

Yes. By connecting the regulator and the MasterShunt on the same MasterBus network, the regulator will adjust its charging voltage based on the actual voltage measured at the battery terminals, compensating for voltage losses in the cables.

How to prevent the alternator belt from slipping under heavy load?

If the alternator demands too much torque and causes the belt to slip, you can activate the Power Curve function via the MasterAdjust interface. This reduces the charging current and minimizes the mechanical load on the engine.

Which direction must this alternator rotate?

The Alpha Compact 28/150 alternator is designed to operate with a clockwise rotation (clockwise direction).

What to do if the Alpha Pro III regulator flashes?

The LED indicator flashes on the regulator serve as alarm signals. For example, 3 short flashes every 2 seconds indicate that the field current is too high, while 2 flashes indicate an overvoltage condition on the battery.

How does temperature compensation work for a 24V system?

The regulator automatically adjusts the charging voltage based on battery temperature. For a 24V bank, compensation is -60 mV per degree Celsius (calculated from -30 mV/°C for 12V), ensuring safe charging and extending battery lifespan.