Drag racers are using 1000a controllers (sometimes several) to control brushed motors typically. If the controller fuses (turns into a fused mass), power is sent directly to the motor for a wild ride into the accident files. A boat typically has a much weaker power-to-wieght ratio, and would gently go up to hull speed as if at WOT. It's doubtful the boat would be accelarating out of control, however.
Reliabiliy is important in a boat, and a disconnect is just another electromechanical interface to go bad. A battery selector switch serves the same purpose, and it's contacts are cleaned each time the switch is rotated.
If you choose to use a brushless motor and controller, a fused controller will melt down your batteries instead, so make sure you have a fuse, rated at twice your peak draw, somewhere in the string.
Be Well,
Arby
After 17 months of part-time building my 21' launch, I'm wrapping up construciton and starting to work out wiring details.
I try to glean all I can from this group and the EV folks. Something I see in the cars, but not so much in boats is an emergency disconnect switch in case of powertrain runaway.
It seems that it might be really handy in the event of a failure to be able to totally disable the battery bank without leaving the helm.
The EVs sometimes use "big red switches" within reach of the driver, and sometimes use a mechanical cable to actuate a switch remotely.
Since I want to keep the battery bank wiring as short as possible, I'm leaning toward the latter method.
This disconnect would be in addition to the keyswitch actuated battery bank contactor and typical fusing.
Any thoughts?
-Tom
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