Furuno RC-1800T - Power Supply Cable; Cable to be Connected to 24 Vdc Battery

4.3 Power supply
4-7
4.3.2 Power supply cable
1) Cable to be connected to 24Vdc battery
The gauge of the battery cable is determined by carrying current and line length. Select
the cable so that the cable loss is limited to 3 to 5 %. The method of calculating the
cable loss is shown in the following:
* Voltage drop in cable (V): e = (K x I x r x L)
* Line length of cable (m): L = (1000 x e) / (K x I x r)
where,
K = coefficient (single-phase/DC: two- and three-phase: √3)
I = current (A)
r = resistance (ohm/km)
L = cable length (m)
Table 4.3.1 Resistance of DPYC (two-core) cable
Conductor Resistance:
At 20 degrees
(ohm/km)
Sectional
Area
(mm
2
)
Wires Dia.
(mm)
Conductor
Outer Dai.
(mm)
Outer Dai.
(mm)
No Gilding With Gilding
1.5 7/0.52 1.56 11.7 12.1 12.2
2.5 7/0.67 2.01 12.8 7.41 7.56
4 7/0.85 2.55 13.9 4.61 4.70
6 7/1.04 3.12 15.2 3.08 3.11
10 7/1.35 4.05 17.1 1.83 1.84
16 7/1.70 5.10 19.4 1.15 1.16
25 7/2.14 6.42 23.0 0.727 0.734
35 7/2.52 7.56 25.5 0.524 0.529
50 19/1.78 8.90 29.4 0.387 0.391
For example, the line length (Lm) of the battery cable DPYC-35 is calculated as follows.
If it is assumed that the cable loss is 3 %, e = 0.72 V, r = 0.542 ohm/km, and I = 40 A,
the line length of the cable is:
L = (1000 x e) / (K x I x r) K = 2
L = (1000 x 0.72) / (2 x 40 x 0.542)
= 16.6 m
If it is assumed that the cable loss is 5 % and e = 1.2 V:
L = (1000 x 1.2) / (2 x 40 x 0.542)
= 27.6 m
Refer to table 4.3.2 to 4.3.5