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Advice Building an electric boat

Msg43

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Hi all! Newbie here so forgive me for my inevitable mistakes. I have searched the forum for similar threads but might have missed them so I am taking the plunge and posting my own question.

I am converting a 1953 wood boat (42' long, 25,000lbs) into an all electric boat. Don't ask me why. I got the idea and before I knew it I was in too far to quit. :)

Propulsion is 2x Elco EP-70s. They require 108V power. My goal is to have a nice 6-8 hour cruising day without having to fire up the genset. My basic math (could be wrong!) is that I will need about 1000Ah of battery power at 108V to accomplish this. I figured I could get to 900Ah with three sets of 36 LIFEPO4 302Ah cells. Rough cost for just the cells shipped to me = 25K.

It seems like the BMS is the sticking point. Of course I don't mind paying up for a premium BMS because I want the ship to be safe and I'd like the bells and whistles of being able to monitor every last cell from my iphone or something. The problem is that the BMSs that I have been able to find which are marine-focused (and ideally have NMEA2000 compatibility) seem to only work with their own vertically integrated brands like Lithionics. Those systems are appealing for their high quality but the price premium for the integrated batteries system is ENORMOUS. In a system this large it seems worth it to consider other options.

Can anyone point me in the right direction or just give friendly advice?

Thanks!

Matt
 

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Cool boat. Not sure what the WB forum would have in the way of BMS advice, it it is a good place for wooden boats, although it’s pretty dead activity wise these days.

As far as a BMS goes, having cell level monitoring on the NMEA2000 network isn’t really necessary, and having that info displayed in a way that made sense would likely be done with a display piping just NMEA data like a maretron display. That’s a lot of wasted money for info that is already easy to display and monitor. Rec, Orion and Emus all make Bms’s that are capable of handling the voltage you’re looking at getting. All have CANbus, and all can be integrated with Victron equipment, including the Cerbo, which makes visualizing what is going on with the battery easy.
 
Cool boat. Not sure what the WB forum would have in the way of BMS advice, it it is a good place for wooden boats, although it’s pretty dead activity wise these days.

As far as a BMS goes, having cell level monitoring on the NMEA2000 network isn’t really necessary, and having that info displayed in a way that made sense would likely be done with a display piping just NMEA data like a maretron display. That’s a lot of wasted money for info that is already easy to display and monitor. Rec, Orion and Emus all make Bms’s that are capable of handling the voltage you’re looking at getting. All have CANbus, and all can be integrated with Victron equipment, including the Cerbo, which makes visualizing what is going on with the battery easy.
That is super helpful thanks. Would an installer know this or is there a vendor who could put that system together on paper for me? Do you suggest just building my own batteries from cells or is there a good battery brand which works with these BMSs but doesn’t have a massive premium? Thanks!
 
That is super helpful thanks. Would an installer know this or is there a vendor who could put that system together on paper for me? Do you suggest just building my own batteries from cells or is there a good battery brand which works with these BMSs but doesn’t have a massive premium? Thanks!
You have to think of batteries as chemistry rather than brand. If you’re thinking brand, then you are thinking of a battery that has been assembled by a vendor and that likely also has an integrated BMS, though not always. As those are set up for 12v or 24v without the possibility of additional series connections, they wouldn’t be suitable for a high voltage build. There are marine electric motor manufacturers that offer their own battery solutions along with controllers. It doesn’t seem that Elco offers anything on the battery front. This leaves you with building a pack. The boat builders that I’ve worked with that have gotten into this realm have all done a lot of research on their end to build battery/propulsion systems. So far those builders have gone with 48v systems such as oceanvolt. From a safety perspective, this is better than HV, however it is limiting when it comes to motor output. As it happens, that’s probably fine for a displacement sailboat, but less so for a motor boat.

So yes, building your own pack would be the most cost effective and possibly easiest way to achieve >100v. LFP would obviously be the safest way to do this (short of LTO, which would be cost prohibitive). Lots of folks have been doing this with Nissan Leaf or Tesla packs. Both are attractive from a system design standpoint. The Tesla trays are 24v a piece and a nice form factor. The problem is that these are the explody types of batteries.
 
Will follow this build.

108 Vdc, wow. Suppose this is necessary at this power consumption (& not having wires massing the boat down). I know you know this, be very careful at this DC voltage level. You may not be able to let go of a DC line at this level.

I built a pulsating 600Vdc bug zapper in college to keep the flying bugs out of the lab while an undergrad. I had to dissemble it after vaporizing bug parts were irritating the HDTV gEEks. We had big bugs in FL. haha ...
 
Just an update. I switched to 48V motors, Victron Inverters, and am using Orion 2 BMS which "talks to" the Victron.
 
Just an update. I switched to 48V motors, Victron Inverters, and am using Orion 2 BMS which "talks to" the Victron.
Glad to hear the project is stilling moving forward. A solar powered pontoon boat is on my daydream list. Unlike your boat mine will have zero character.
 
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Rough cost for just the cells shipped to me = 25K.

I might have used lead acid. Rolls batteries are known to last up to 15 or 20 years if your battery bank is sized properly, and maintained correctly.

Did you take the engines out ? For a floating object to be stable the center of gravity (G) must be below the center of buoyancy.

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The worst has to be getting waked by people in big yachts throwing tsunamis across the channel.
 
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I might have used lead acid. Rolls batteries are known to last up to 15 or 20 years if your battery bank is sized properly, and maintained correctly.

Did you take the engines out ? For a floating object to be stable the center of gravity (G) must be below the center of buoyancy.

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The worst has to be getting waked by people in big yachts throwing tsunamis across the channel.
Err no, the centre of gravity is normally higher then the centre of buoyancy , this provides the “righting moment “ needed
 
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