SMA SUNNY ISLAND 8.0H - Setting the Resistance of the Battery Cable

7 Commissioning SMA Solar Technology AG
100 SI80H-60H-OffGrid-IA-en-11 Installation Manual
7.12 Setting the Resistance of the Battery Cable
You can optimise battery management by setting the resistance of the battery cable in expert mode.
Figure27: Designation of cables
The resistance of the battery cable is composed of the resistances of cable 1, BatFuse and cable 2.
Requirement:
☐ In a cluster, the Sunny Remote Control must be connected to the master.
1. Calculate the resistance of the cables. Use the following formula:
R
CU
(l,A) = ρ
l
⁄
A
R
CU
(l,A) = Resistance of the cable
ρ = specific resistance of copper (ρ = 0.018
Ωmm²
⁄
m
)
l = Total length of conductor (outward conductor + return conductor = twice the cable length)
in m
A = Conductor cross-section in mm²
2. Calculate the total resistance of the battery cable. Use the following formula:
R
BatRes
= R (cable 1) + R (BatFuse) + R (cable 2)
R
BatRes
= Total resistance of the battery cable
R(cable1) = Calculated resistance of cable 1
R (cable 2) = Calculated resistance of cable 2
R (BatFuse) = Total resistance of the BatFuse = 2 m Ω
3. Switch to expert mode (see Section 7.6).
4. Select the 221.06 BatWirRes parameter and set it to the resistance of the battery cable.
BatFuse
battery
Off-grid inverter
cable 1 cable 2
Length l
1
Length l
2