Electrical Connection of the Sunny Backup 2200
SMA Solar Technology AG
50
SBU2200-TEN083320
Technical Description
7.2 DC Connection
7.2.1 Grounding
Calculating the Protective Earth Conductor Cross-section
SMA Solar Technology AG cannot calculate generally valid values for the required cross-section of
the grounding cable for external grounding of the battery. The conductor dimensions depend on the
type and size of the battery connected, the external fuse (DC side) and the material used for the
grounding conductor.
The required cross-section of a (copper) protective earth conductor can be calculated using the
following formula. Trigger times of about 25 ms are typical for short-circuit currents between 2000 A
and 10000 A.
A grounding conductor of 16 mm² cross-section is thus adequate for short-circuit currents up to
10000 A.
WARNING!
The Sunny Backup 2200 does not have an internal DC fuse.
• Install an external DC fuse with 125 A between the Sunny Backup 2200 and the
battery.
External grounding
The external grounding of the battery's negative pole is normally possible since the
batteries and the grid side are galvanically isolated from one another in the Sunny Backup
2200. In this case, make sure that the high currents that may occur under fault conditions
can be adequately discharged.
If a ground connection is necessary, it must be established separately by an installer
outside of the Sunny Backup 2200.
Determining the cross-section
Exact calculation of the protective earth conductor cross-section must take account of the
regionally applicable standards and guidelines (e.g DIN VDE 0100 Part 540).
t = Short-circuit duration in seconds
I
SC
= Maximum battery current (short-circuit current) in amperes
S = Cable cross-section in square millimeters
