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n

PLUS phase

Most Mastervolt battery chargers are

equipped with an extra step, the PLUS

phase. During periods when the battery is

resting, an absorption cycle lasting one

hour will take place every 12 days to

ensure that the battery stays in perfect

condition.

n

Return Amps

During the absorption phase, the battery

accepts progressively less current. Once

the charge current remains under a

certain level for a given period of time,

the battery is considered to be fully

charged. This maximum charge current

is called the Return Amps, and the

corresponding period the Return Amps

Time. The battery charger takes this as

a signal to switch over to the next step,

the float phase. Just like many other

parameters of the battery charger,

Return Amps and Return Amps Time can

be set by the installer with the help of

software that is freely available on the

Mastervolt website. In fact, the installer

can use this software to customise the

battery charger to your onboard system

requirements.

BATTERY CHARGERS

n

Which battery charger is necessary for a battery capacity

of 200 Ah and a 100 Ah starter battery?

The starter battery is generally not considered when calculating the charger

capacity – it is only used for starting the engine and will therefore tend to be

only partially discharged if at all. While you are using the engine, the alternator

recharges the battery and when connected to the grid, it is charged via the

second output of the Mastervolt battery charger. As a rule of thumb, a charge

capacity of 25 % (up to 50 % for Gel batteries) of the battery capacity is sufficient

to charge the battery quickly and safely, and also power the onboard systems.

For a battery of 200 Ah, for instance, a battery charger of 50 amps would be

appropriate.

n

Is having 10 % of my battery capacity as charge capacity

sufficient?

Definitely not. You can assume 25 % and up to as much as 50 % with Mastervolt

batteries. The old 10 % rule was common in the days when battery chargers

had no current and voltage regulation, and too high a current could overcharge

the batteries. Mastervolt battery chargers have perfect current/voltage

regulation and are also equipped with a temperature sensor that ensures the

voltage is regulated according to the battery’s temperature. Several loads are

connected while charging the batteries and these loads are also powered by the

charger so the available charge current for the batteries will be reduced.

n

Can multiple battery chargers be parallel connected?

In addition to simply being chargers, Mastervolt battery chargers also provide

power for the 12 or 24-volt onboard system. They can easily be parallel

connected should you wish to increase capacity. In fact, this is often the

only way to power your 12 or 24-volt system with the 230 or 400-volt power

connection. Similarly, should you need a charge current higher than 100 amps,

several battery chargers can be parallel connected. A parallel system with

multiple battery chargers does not require any special equipment. It can be

installed in exactly the same way as a single charger, except that each charger

will have its own cables leading to the battery or the DC distribution.

Wiring for the voltage compensation is also connected separately for each

charger. The temperature sensor for each charger needs to be separately

connected to the battery that you expect to reach the highest temperature. If

the chargers and sensors are properly linked, the charge current will be evenly

distributed over the connected chargers.

The possibility remains that one of the chargers will switch to the absorption

phase sooner than the others. This is a perfectly normal phenomenon caused

by tolerances in the adjustment, with no effect on charge time and charger

operation. When parallel connecting multiple battery chargers, we recommend

that they be of the same model, type and charge capacity. For instance, when a

100-amp charger is linked parallel to a 50-amp charger, the charge current will

not be evenly distributed over both. Although this will not affect the charging

process or be detrimental for the chargers, it is more efficient to install two

chargers of 75 amps each.

n

How can I charge batteries with

limited power?

When multiple large battery chargers are

parallel switched, the available 230-volt

connection is often insufficient. Connect

one of the battery chargers to prevent the

AC connection from overloading. Although

this will increase the time needed for

charging, you are normally connected

to the grid for a longer period of time

(overnight) anyway. Both battery chargers

can be powered if the generator is running,

as the generator usually delivers more

output than a power connection. The two

battery chargers will not cause the power

connection to be overloaded. Another

possibility is equipping the vessel or vehicle

with two 230-volt connections.

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