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Le 29/10/2020 à 21:46, Karen Smith via
groups.io a écrit :
Our SM#160 bow thruster draws about 485 Amps when it is running.
The exact power calculation is complicated because the voltage is
not steady at 24 volts, but drops quickly, and significantly,
under this load. The reason the wire looks undersized by standard
calculations is that it operates on a very short duty cycle, so
heating of the wire is minimal. If you were to try to push 500
Amps through that wire for an hour, you'd have a real problem.
At least on our boat, the "bow thruster" cable carries all the 24V
power to everything forward of the forward saloon bulkhead. Mast
and genoa furlers, cabin lights, nav lights, windlass...
We have fused our battery bank in two different ways, and both
worked well. Keep in mind we have a bank of 4 pairs of batteries,
smaller than yours which I believe is 6 pairs.
Our batteries were first fused with four 125 Amp rated battery
terminal fuses, one on each 24V positive, for a total of 500 Amps.
With 6 pairs of batteries you'd end up in the about same place
with 80 or 90 Amp rated fuses. When we changed battery brands,
the terminal fuse holders no longer fit under the battery box lid,
so we switched to a singe 500 AMP ANL-style fuse. Never have any
of these tripped.
We have also reworked the whole 24 volt distribution system so
EACH of the wires leaving the battery box has a fuse appropriate
to its ampacity, and the switches now interrupt current to
everything except the bilge pump circuit. To me this is a really
basic safety issue. If there was ever to be an electrical fire on
the boat, or a piece of runaway equipment, I need to know I can
shut off the power to everything
On the boats I have seen, Amel was very inconsistent about what
wires they connected to which side of the main switches. On our
boat, only the battery charger, bilge pump, and "always on 12V
converter" were connected to the unswitched side. I think on later
boats they just ran out of space on the stud on the switched side,
so were forced to move wires to the unswitched post.