Electric RIB Dinghy

[aybabtme]

Hello!
I'm planning to put a 6kW electric outboard on a 3.1m rigid inflatable dinghy, specifically these two things:

• ePropulsion Navy 6.0 is a 6kW, 48V outboard that expects between 39 and 60V and is "rated for 125A" (whatever that means, assuming this is the max it'll pull at 39V).
• Highfield 310 Classic is a 3.1m RIB with an aluminum double floor and a front compartment that can "fit a 24L fuel tank". I already own the dinghy and my quick measurements of that compartment gives me a rough box of L:34cm (13.5") W:40cm (16") H:19cm (7.5"). I started building a cardboard prototype to get a better idea of how big of a box I can fit in there.

My idea is to make a 14s36p battery with LG MJ1 cells and an unknown-yet BMS (maybe one of these Daly 14s 150A separate port?) to fit in the front compartment, where the fuel tank would usually go. I hope this would give me 1h autonomy at full throttle, and I don't think I'll need more than that in my current location. I'd probably make the battery box with fiberglass, and make sure it's waterproof as much as possible (the RIB's forward compartment is enclosed and dry-ish but can get wet via the bilge when the dinghy bounces around).

I've built a smaller ~700Wh pack with NMC cells before (for practice mostly, and general use) and a larger 8kWh pack with LFP cells (sailboat house battery). I have a spot welder (the kWeld with capacitors) and was planning on using 0.3mm by 7mm pure nickel strips for inter-cells connections. I'm not sure how I'd connect the main poles to these nickel strips to amount to the required 125A. It seems I'd be good with approximately 2/0 cables to keep everything cool (I already have them around, so I don't mind oversizing them).

• Do you have any recommendations, or gotchas, I should be aware of?
• How would you do the layout?
• Do you recommend another cell than the LG MJ1?
• Where would you source these cells?
• Do you recommend another BMS? Where would you source it?
• Where would you source the BMS?
• How would you build the enclosure? Do you know where I could find a pre-made one that would fit the dimensions?
• What sort of connectors would you use for the charge and discharge ports?
• Where would you source these connectors?
• What specific model of charger would you use?

 

[Balmorhea]

Because you have room, and because you want several kWh of capacity, I think it’s a mistake to use small cells like that. You’ll have hundreds of unnecessary places for a problem to crop up, and it will take you who knows how much added time to construct your pack. It’s like building your house out of Lego just because you're familiar with it.

My suggestion is to use automotive cells, or some other large format pouch or prismatic cells.

 

[aybabtme]

Which cells and manufacturer in particular would you recommend, and where to source them? I don't know anything about NMC in prismatic or pouch format.

 

[amberwolf]

depending on your requirements, there are the eig nmc c020 cells. jimbob01 has some new-old-stock in the for sale section of this forum, along with the specs and measurements and such.

used nissan leaf cells could work, as well.

i'm sure there's others (jonescg has tested a number of different pouch cells in various posts/threads over the years), but i don't remember any specifics besides the eig (because i've using those for years myself).


based on the dimensions you give, i think you could fit at least 14s2p (52v 40ah, 2kwh), and possibly 3p (60ah, 3kwh), of these 20ah cells. the 2p would make one big block; you might have to do the rest in sections around it.

 

[pilotarix]

Hi,

Interesting post since I am also looking into an Epropulsion Navy motor for my Dinghy. I currently use the Epropulsion Spirit 1.0 an older version that works fine but has only 3hp. I would like to upgrade to a Navy 3.0 or 6.0 and make my own battery.
Do you get any further with your project so far?

Thanks
Chris