TECHNOLOGY
EN / Alpha alternator - Alpha Pro regulator / June 2007 7
3 TECHNOLOGY
This user’s manual describes the installation and
operation of the Alpha Alternator together with the
Alpha Pro regulator from Mastervolt. This charging
system is designed to give high output with low
RPM, which is typical for marine applications. It
consists of the following main components (See
figure 1):
1 Alpha alternator (included)
2 Alpha-Pro charge regulator (included)
3 Batteries and fuses (not included)
Fig.1: Basic principle of a charging system
consisting of the Alpha Alternator together with the
Alpha Pro regulator
3.1 ALPHA ALTERNATOR
Mastervolt Alpha alternators are specially designed
to provide high power even at low RPM. A pulley
ratio of 1:2 – 1:3 and an engine idle speed of around
700-800 rpm will generate substantial current for
charging the battery sets and powering the
connected equipment.
Mastervolt alternators are resistant to the high
temperature of the engine room, allowing the engine
to serve as the energy source for onboard
consumers and as a quick charger for the service
and starter batteries.
3.2 ALPHA PRO REGULATOR
The Alpha Pro voltage regulator controls the
alternator’s output voltage. It is designed for optimal
recharging of both wet, gel and AGM batteries.
Battery charging is accomplished in three automatic
stages: BULK, ABSORPTION and FLOAT. Simple,
automatic operation is made possible by the
microprocessor that is the brain of the Alpha Pro
regulator
3.2.1 Three step charging system
Figure 2: Three step charge system
See figure 2. The first step of the three step charge
system is the BULK phase (A), in which the output
current of the charging system is limited by the
maximum output current of the alternator and the
engine RPM. At this stage the major part of the
capacity of the battery is rapidly charged. The
current charges the batteries and the voltage will
rises to the absorption voltage of 14.25V (12V
models) or 28.5V (24V models) @ 25°C / 77°F.
The duration of this phase depends on the ration of
charging capacity versus battery capacity and on the
degree to which the batteries were discharged to
begin with.
The bulk phase is followed by the absorption phase.
(B). The absorption charge starts when the voltage
on the batteries has reached 14.25V (12V models) /
28.5V (24V models) @ 25°C / 77°F, and ends when
the battery is fully charged. Battery voltage remains
constant throughout this stage, and the charge
current depends on the state of charge of the
battery, the battery type, the ambient temperature,
and so on. With a wet cell battery this stage lasts
some four hours, with gel and AGM around three.
CHARGE CURRENT
BATTERY VOLTAGE
BULK
ABSORPTION
FLOAT
TIME
ALPHA PRO
REGULATOR
ALTERNATOR
BATTERIES
FUSES
TEMPERATURE
SENSOR
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