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Absorption phase

The second stage in a modern

3-step+ charging process.

Batteries are charged from around 80 %

up to 100 % during this stage. Voltage is

somewhat lower than the gas voltage of

the battery, which is 2.4 volt per cell at

20 °C (or 14.4 volt for a 12-volt and 28.8

volt for a 24-volt battery). The absorption

phase follows the bulk phase and is, in

turn, followed by the float phase.


ABYC standards

The American Boat & Yacht Council is a

non-profit organisation that represents

American builders. It sets standards

and gives recommendations for

nautical equipment (including electrical

equipment) on pleasure vessels with the

goal of enhancing

safety. The ABYC

therefore issues

certification for



AGM battery

Battery in which the electrolyte (a mix

of water and sulphuric acid) is largely

absorbed in glass fibre matting. As these

batteries are entirely maintenance-free

and do not normally produce gas, they

can be fitted anywhere and ventilation

is usually unnecessary. Thanks to their

construction, AGM batteries can be

swiftly discharged while providing a very

powerful current. This makes them highly

suitable for systems that require high

levels of current, such as bowthrusters,

winches and engine starting.


Alarm contact

A contact in a battery charger or inverter

that is activated when an external or

internal malfunction occurs.


Alternating current (AC)

AC is the electricity that for example

comes out a socket in your home.

Other terms used for AC include shore

power, generator power or inverter



Battery acid

An electrolyte that consists of water

and sulphuric acid. The specific gravity

of battery acid in a charged battery

varies between 1.28 and 1.30.


Battery charger

Used to charge batteries. Its capacity

should be at least 15 to 25 % of the

battery capacity with a flooded battery

and max. 30 % with an AGM battery, up

to 50 % with a Gel battery and up to

100 % with a Lithium Ion battery.


Battery Management System

A natural phenomenon of Li-ion

batteries is the natural imbalance

between stronger and weaker cells.

In the charging process, one or more

cells will reach their maximum charge

level faster due to this imbalance,

while others do not get fully charged.

The lower cells will be discharged

faster, causing the battery to be

empty sooner due to under-voltage

and so reducing the lifespan of the

battery. To prevent this, Mastervolt

Lithium Ion batteries are equipped

with a Battery Management System

that automatically compensates for

the imbalance between the cells and

increases the lifespan and the total

capacity of the battery.


Battery monitor

Indicates the battery status. Mastervolt

offers a selection of 4 models. Firstly,

the BattMan with spray-proof display

and energy meter, which is available

in two models. Next is the Masterlink

BTM-III with detailed battery infor-

mation via the LCD display and LED

bar. The modern MasterShunt com-

bined with the EasyView 5 provides

detailed information on voltage, cur-

rent, and historical and user data. It is

easily installed within the MasterBus

network, with touchscreen controls for

all functions. See pages 114-115 in this

Powerbook for more information on

the battery monitors.

AC voltage changes polarity with a given

frequency: In Europe, for instance,

the polarity of the electrical voltage

is reversed 50 times per second. The

supply therefore has a frequency of 50

hertz (Hz).



Amperian is a powerful digital assistant

that monitors your Mastervolt system

anywhere in the world. Amperian allows

you or your system provider to remotely

operate and monitor your power system.

The Amperian

Interface makes

all system data

available online.


Amps (A)

The unit that measures the current

following through a circuit. The current

can be calculated by dividing the voltage

by the resistance of the consumer.

A resistance of 6 ohm and voltage of

12 volt gives a current of 2 amps.


Amp-hour (Ah)

The unit that denotes the capacity of a

battery, calculated by multiplying current

in amps by the duration of the discharge

in hours. For example: If a battery

delivers a current of 5 amps in 20 hours

with the voltage constantly above 10.5

volt, this amounts to 20 x 5 =100 Ah.

The capacity of a battery usually

depends on the amount of lead and

battery acid it contains.



Converts chemical energy

into electrical power and vice

versa. The nominal voltage of a battery is

2 volt, and higher voltages are achieved

by connecting several batteries in series.

For instance, six 2-volt batteries can be

combined to provide a nominal voltage

of 12 volt.



Technical terms - glossary