Power Distribution and Balance
Selecting the proper location of the power connection to the NMEA 2000 network depends on the length of the
backbone and the power needs of the devices on the network.
For the NMEA 2000 network to work properly there must not be more than a 1.67 Vdc drop in the supply
voltage between the T-connector with the power cable and the NMEA 2000 device located farthest from this T-
connector.
To determine the voltage drop in your NMEA 2000 network, use this equation:
Voltage
= Resistance
drop
Cable resistance
(ohms/m)
Voltage
=
drop
Garmin cable resistance
value = 0.053
Voltage drop = resistance × distance × load × 0.1
Resistance: Refers to cable resistance (ohms/m). The Garmin cable resistance value is 0.053.
Distance: Refers to the distance from the power connection to the device located furthest away on the network
(in meters).
Load: Refers to the network load. The network load is the sum of the LEN numbers of all devices from the
power connection to the end of the network.
When evaluating the results of your calculation, consider the following:
• If you calculate a voltage drop of 1.67 Vdc or less, you can connect power to either the end or the middle of
the NMEA 2000, and it will function correctly.
• If you calculate a voltage drop of more than 1.67 Vdc, you must connect power to the middle of the NMEA
2000 network. The location of the power connection in the network depends on the network load and
distance from the battery. You should try to balance the voltage drop equally on both sides of the power
connection.
• If a voltage drop of under 1.67 Vdc is not possible on the NMEA 2000 network, contact a professional
installer for assistance.
8
× Distance
Distance from the
power connection to
×
the furthest device (in
meters)
End-Powered NMEA 2000 Network Designed Correctly
Power cable
Length = 2 m
Drop cable
Length = 2 m
Drop cable
Length = 6 m
Drop cable
Length = 4 m
× Load
Network load
Sum of the LEN numbers
×
from the power connection to
the end of the network
× 0.1
× 0.1
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