Victron energy Phoenix 12/30 (1+1) Bedienungsanleitung Seite 8

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4.13. Automatic voltage compensation
The charger compensates for the voltage drop over the DC cables by gradually
increasing the output voltage if the charging current rises.
The fixed voltage offset is 100mV. The voltage offset is scaled with the charge
current and added to the output voltage. The voltage offset is based on 2x 1-
meter cable, contact resistance and fuse resistance.
Example calculation for the 12/50 (1+1):
���� × ����
���� =
The cable resistance R can be calculated with the following formula:
����
Here R is the resistance in ohms (Ω), ρ is the resistivity of copper (1.786x10^-8
Ωm at 25°C), l is the wire length (in m) and A is the surface area of the wire (in
m²).
A widely used distance from charger to battery is 1 metre. In this case the wire
length is 2 metres (plus and minus). When using a 6AWG cable (16mm²) the
1,786 × 10 × 2
−8
������������ ���� ���� = = 2.24����Ω
wire resistance is:
16 × 10
−6
Installing a fuse close to the battery is highly recommended. The resistance of a
�������������������� = 0.720����Ω
standard 80A fuse is:
The overall resistance of the circuit can then be calculated with the following
������������������������ = ������������ ���� ���� + ��������������������
formula:
������������������������ = 2.24����Ω + 0.720����Ω = 2.96����Ω
Therefore:
The required voltage drop compensation over the cable can be calculated with
���� = ���� × ���������������� ���� ����
the following formula:
In which U is the voltage drop in volts (V) and I is the current through the wire in
amperes (A).
���� = 50 × 2.96����Ω = 148�������� for the full 50A charging current.
The voltage drop will then be: