Samlex America DC-3500-KIT - Manuel (Page 5)

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The size (thickness / cross-section) of the conductors is designated by AWG (American
Wire Gauge). Please note that a smaller AWG # denotes a thicker size of the conductor
up to AWG #1. Wires thicker than AWG #1 are designated AWG #1/0, AWG #2/0,
AWG #3/0 and so on. In this case, increasing AWG # X/0 denotes thicker wire.
DC input circuit of an inverter is required to handle very large DC currents. Cables
and connectors from the battery to the inverter should be properly sized to ensure
minimum voltage drop, minimum heating and minimum power loss between the
battery and the inverter. Thinner cables and loose connections will result in larger
voltage drop, increased loss of power and consequent reduction in efficiency, poor
inverter performance and will produce abnormal heating that may lead to risk of
insulation melt down and fire.
for safety against overheating and consequent deterioration of the insulation and
possibility of fire, the National Electrical Code (NEC) specifies the maximum current
carrying capacity (Ampacity) of various types of cables for installation in free air.
Apart from the consideration of safety as explained above, reducing the voltage
drop as a result of longer distance of the cable between the battery and the inverter
is also important for improving the efficiency of the DC input side of the inverter
system. longer distance between the battery and the cable will require thicker cable.
Normally, the thickness of the cable should be such that the voltage drop from the
battery terminal to the inverter is as low as possible, preferably less than 5%.
Inverters are designed to operate normally within a specified lower and upper input
voltage range. The lower operating voltage limit of inverters is normally 10V, 20V and
40V for 12V, 24V and 48V battery systems respectively. When this limiting voltage is
seen at the input terminal of the inverter, it will shut down due to low input voltage
protection. Thus, if there is excessive voltage drop in the input connection between
the battery and the inverter due to thinner cable / longer distance / larger current, the
inverter will shut down even if the battery is fully charged.
As the distance between the battery and the inverter may vary depending upon the
user requirement, 10 ft length of cable is provided in the Inverter Installation Kits for
convenience. The specifications of the Kits include the approximate voltage drops for
distances of 3, 6 and 10 ft. between the battery and the inverter.
Please note that for the purposes of the calculation of the voltage drop based on the
resistance per unit length, the length of the cable has been taken as twice the distance
between the battery and the inverter to include the overall length of the Positive and
Negative cables (e.g. if the distance between the battery and the inverter is taken as
3 ft., the length of the cable has been taken as 6 ft. for calculation purposes).
Please ensure that the distance between the battery and the inverter is kept as short
as possible to limit the voltage drop to less than 5%. cut off the extra length of cable
if the distance between the battery and the inverter is less than 10 ft.
sectIOn 2 | General