Tesla modules in boat

3283 Views 80 Replies 10 Participants Last post by remy_martian, 2 mo ago

Ohno

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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kennybobby

· #4 · 4 mo ago (Edited)

From what i remember, the 2 boeing 787 screamliner APU starter battery fires were contained in aluminum boxes; their "fix" was to build a vault to hold this 36V 8s lithium pack with a vent tube to exit the airplane outer skin in the event of another fire. There are other lithium packs for other functions in the electronics bay, but they are not in any vault and they don't have the same 4-level bms, and probably aren't held on a full-voltage trickle charge at all times during a flight.

i think you could build an aluminum battery holder and be fine with a good bms and attention to not over-charging. And a good fire and smoke alarm system to let you know if you need to get out quick.

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kennybobby

· #14 · 3 mo ago

Contactors between parallel packs are used to isolate them in the event one side has an internal issue. See Wolftronix threads about integrating the BMS with the contactors.

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kennybobby

· #16 · 3 mo ago (Edited)

In a catamaran with packs in each hull, should the connecting wires be de-energized when the vehicle is Off, or will they be Hot all the time?

If using used modules from a wrecked car, then just assume that you will have a fire--are you wanting to save the vehicle or just save your life? Is it just a run-about type of boat or a live-aboard?

An EV has safety aspects to protect first responders in the event of a crash that a Boat doesn't necessarily need, just depends upon your level of risk tolerance.

Cool boat build

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