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Tesla modules in boat

3285 Views 80 Replies 10 Participants Last post by  remy_martian
I am converting a 25 hp gas outboard motor to an 18kW electric PMAC motor for use in a hydrofoil assisted power catamaran. Converting an outboard to electric is something I've done a couple of times but this time I'd like to make my battery safer. My last electric boat is a little lacking in the safety department - Electric Foiling Catamaran from Recycled Parts.

This time I'd like to use 6 Tesla Gen2 XS modules. 3 modules will go in a box on each side of the boat. This is a 72v system so I'm thinking that the 3 modules in each box will be wired in series then the two boxes combined parallel.

What I'm hoping you very knowledgable people here can help me with is battery box design. My thought is to make a watertight (within the limits of the IP67 rated vents) steel box out of .050" - .080" thick sheet that fits fairly close to the size of the 3 modules. That steel box would have a battery box vent Vent valve for battery box - EVcreate
and a layer of furnace insulation on the outside. The steel boxes would be mounted inside of composite boxes that are used as seats and will also hold BMS, contactors, fuses, emergency shutoffs, etc.

This is a carbon/honeycomb boat and I'm fighting to keep the weight down so that I can drag around those heavy batteries without too much performance loss. It kills me to think of 100 lbs of steel boxes onboard but I'm not seeing a way to mitigate the fire risk without something like that. It sounds like aluminum's melting temperature is not up to the job.

Any thoughts? Am I overthinking this? I'm not pulling a lot of current, maybe 200 amps continuous. I think that's like .5C. Charging C rate would be substantially lower.
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Tesla cells have vents that release hot gases (cave men gave these hot gases the name "fire"), so there is no pressure...they go off like little bottle rockets, and once they cutting torch their was through the passenger compartment floor, they launch into the cabin and fly around in it until the chemical reaction stops.

Once the cooling system fails, each cell heats its neighbor, lighting it off. Significantly less than boiling water temperatures will light them off, so do the math with a neighboring cell at several thousand degrees, about 2 or 3 mm away from the cell that hasn't lit yet.

The job is to ensure they don't light off.

The job is to isolate the cells/modules if they do

The job is to give occupants time to egress before the car melts.

The job in a boat is to egress the boat into water with sharks, Great Whites (yes, they live in the Pacific Ocean, off the Left Coast), in it...oh wait, let's keep the people on the floating boat and get rid of the worthless burning battery.
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