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Connection wire dimensions:

ELECTRICITY

The right wiring

Having the right wiring is crucial for safety and efficiency. Incorrect diameters can

lead to overheated cables and cause a fire. This is not just theory; vessels and RV’s

are lost every year due to onboard fires that are often caused by faulty wiring.

As well as being safer, a proper cable thickness also ensures that your battery

charger and inverter perform to their best. Using thinner cables than recommen-

ded between the battery charger and inverter and battery (set) could lead to excess

voltage loss through the cables, resulting in an excessively low charge voltage on the

battery terminals. This in turn means the batteries are insufficiently charged, which

has a negative impact on their lifespan. Using thinner cables than recommended

for the inverter will prevent you from using the maximum capacity of the batteries.

In this case the high (cable) losses cause the DC input voltage of the inverter to be

(much) lower than the actual battery voltage, which makes the inverter switch off

too soon and not use the full battery capacity. This is why people often use thicker

cables than required.

As lower voltages also involve higher

currents, it is even more important to use

the correct cable thickness.

The current (A) is higher because direct

current with 12 V or 24 V is lower than

alternating current with 230 V while the

(required) power stays the same.

As a result the current will increase as

P = V x I.

The rule of thumb below can be used:

n

For 12 or 24 V DC systems, 3 amps

power per 1 mm² cable diameter

applies.

n

For 230/120 V AC systems, 6 amps

power per 1 mm² cable diameter

applies.

Generating

electrical power

There are various ways to

generate power:

n

With an onboard petrol or diesel

generator (usually AC, also

available in DC).

n

By the alternator(s) on the main

engine.

n

Grid (AC).

n

Solar panels (DC).

n

Wind generator (AC or DC).

Conversion

Generated energy can be used

immediately or stored in the

batteries using a battery charger.

A battery charger converts the AC

voltage into DC voltage. An inverter

usually converts a low DC voltage

of 12/24 volt into an AC voltage of

230/120 volt, 50 or 60 Hz.

You may also encounter DC-DC

converters; these devices convert

DC voltage into another DC voltage,

for instance 24 V from a battery

to 12 V to power your navigation

equipment.

Please note:

Designing a complete electrical

system requires detailed knowledge,

experience and information

(the subject has filled entire

encyclopaedias!). The specialised

Mastervolt dealers are at your

disposal.

Conductor

diameter

(mm

2

)

Current acc. to

rule of thumb

DC

Current acc. to

rule of thumb

AC

American

Wire Gauge

AWG

0.5

1.5 - 2 A

3 - 4 A

20

0.75

2 - 3 A

4 - 6 A

18

1

3 - 4 A

6 - 8 A

17

1.5

4 .5 - 6 A

9 - 12 A

15

2.5

7.5 - 10 A

15 - 20 A

13

4

12 - 16 A

24 - 32 A

11

6

18 - 24 A

36 - 48 A

9

10

30 - 40 A

60 - 80 A

7

16

48 - 64 A

96 - 128 A

5

25

75 - 100 A

-

3

35

105 - 140 A

-

2

50

150 - 200 A

-

0

70

210 - 280 A

-

2/0

95

285 - 380 A

-

4/0

Example:

If a battery or battery charger provides an expected current of 75 amps,

you require a cable of at least 25 mm².

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