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Can Lithium batteries support an AGM installation for Solar Powered Catamaran

agm's a re a terrible idea for electric propulsion, 300 cycles? that's one year
i Mix 1045ah of AGM at 12v and 2kw of lithium also at 12v on a sailboat because I can't risk a BMS failure killing all communications, navigation, nav lights etc, and I have that amount of storage because I like to run the air conditioning in silence, I use the generator every few days to supplement the 2kw of solar.
I'd recommend 32prismatic Lifepo4 in series with a 32S BMS rated for the amperage of both motors, but truthfully you should have 2 p6v banks incase one fails.
I beleieve one of the ev's maybe a leaf has 96v batteries that could be adapted. Jehu Garcia probably has something that would work, but you have more to consider, 12v batteries charge at around 14v 48v batteries charge at around 52v so 96v will charge in the 104v range, most MPPT chrgers need 20-30% higher voltage so you'll need enough solar panels in series to give say 150v.
I don't know who makes MPPT chargers in that range.
the gas outboards are starting to look better to me.
 
Joe Delaney said:
agm's a re a terrible idea for electric propulsion, 300 cycles? that's one year
i Mix 1045ah of AGM at 12v and 2kw of lithium also at 12v on a sailboat because I can't risk a BMS failure killing all communications, navigation, nav lights etc, and I have that amount of storage because I like to run the air conditioning in silence, I use the generator every few days to supplement the 2kw of solar.
I'd recommend 32prismatic Lifepo4 in series with a 32S BMS rated for the amperage of both motors, but truthfully you should have 2 p6v banks incase one fails.
I beleieve one of the ev's maybe a leaf has 96v batteries that could be adapted. Jehu Garcia probably has something that would work, but you have more to consider, 12v batteries charge at around 14v 48v batteries charge at around 52v so 96v will charge in the 104v range, most MPPT chrgers need 20-30% higher voltage so you'll need enough solar panels in series to give say 150v.
I don't know who makes MPPT chargers in that range.
the gas outboards are starting to look better to me.
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This idea is terrible. Sailor here. Electric is ok as an aux with sails. But if you want to do more than a planned circuit route of limited range this idea is doomed. Sailboats converted to electric aux power lose value. You dont have sails.
Say you have a range if 50 miles. You leave and go 40 miles. Weather changes, storm ahead. Not enough power to get to port. No sails. No solar.
What do you do?
 
.Samo. said:
I'm planning a 96v setup for my boat too. So interesting discussion.

Looking at other eboat conversations, the tend to need very little power at displacement speeds, and that's hull dependant. After that power requirements are exponential.

Good displacement hulls are long and thin (higher displacement speeds), so a cat is likely to be the perfect choice!

My boat isn't a cat, it does 5 knots with 5hp and 8 knots at 40hp. That last 3 knots really uses a stack of energy. So electrification for me is displacement mode, max 6 knots, and a 10kw motor, running at around 5kw, is my goal.

I'd be surprised if you need any more than 10kw in each pontoon to hit your displacement speed. Thoughts?

See Candela C-8 for a high speed eboat!
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Many thanks for the reply.
I've been so busy with the cat that I haven't checked in here for a while. I've decided to go with a 48v system as the EPropulsion X series are just too expensive for me. I have ordered six Seplos Mason 15kWh batteries and will use three for each side of the cat. I have been talking to YouTuber Patrick from 'Sailing Elektra' channel. His cat is a 9m one and he uses two EPropulsion Navy 6.0 electric outboards. I'd previously discounted this idea but was reading an article about petrolheads who use two, three and four ICE outboards on their speedboats and I suddenly thought, why don't I use two Navy 6.0 outboards PER SIDE of the cat ie. four in total. The max current draw at 6kw per motor is 125A. My batteries are each capable of at least 200A continuous so should be able to manage even on full throttle. I've emailed EPropulsion this weekend to see what they think, but this could be a real solution as there is space on each transom to fit two. The real test would be in the water as I don't think there is any definitive answer as to how the two would perform as against one bigger one, but the benefits (redundancy, smaller voltage, manageable current, cable size) all look favourable as being the solution.
 
Dave911 said:
This idea is terrible. Sailor here. Electric is ok as an aux with sails. But if you want to do more than a planned circuit route of limited range this idea is doomed. Sailboats converted to electric aux power lose value. You dont have sails.
Say you have a range if 50 miles. You leave and go 40 miles. Weather changes, storm ahead. Not enough power to get to port. No sails. No solar.
What do you do?
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Drop anchor? Drift? Sorry, I couldn't resist. You have to forgive my naiveity as my only sailing experience was a 'pot luck' fortnight in Greece 30 years ago. I have now bought the cat. It's a power cat so there are no sails. It already has two 250litre fuel tanks so I'm thinking of fitting two 5kw petrol generators as a back up system to the electric. The real answer to your concerns is that only through experience will I be able to guage what the range will be, what sea state / weather puts a spanner in these calculations and to err on the side of caution when starting out. Thanks for your thoughts.
 
althemusicwizard said:
Drop anchor? Drift? Sorry, I couldn't resist. You have to forgive my naiveity as my only sailing experience was a 'pot luck' fortnight in Greece 30 years ago. I have now bought the cat. It's a power cat so there are no sails. It already has two 250litre fuel tanks so I'm thinking of fitting two 5kw petrol generators as a back up system to the electric. The real answer to your concerns is that only through experience will I be able to guage what the range will be, what sea state / weather puts a spanner in these calculations and to err on the side of caution when starting out. Thanks for your thoughts.
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Keep in mind that pushing a boat through flat water is entirely different that pushing a boat into storm waves and wind.

Hp requirements can be 2-3x. My sail boat can do 6 knots via the engine in flat water. I had to go directly into the wind in a blow for a few miles and I could only do 2-3 knots at full power as we got beat up from the wind, waves, and spray.
 
Dave911 said:
Keep in mind that pushing a boat through flat water is entirely different that pushing a boat into storm waves and wind.

Hp requirements can be 2-3x. My sail boat can do 6 knots via the engine in flat water. I had to go directly into the wind in a blow for a few miles and I could only do 2-3 knots at full power as we got beat up from the wind, waves, and spray.
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I've been told by the designer of the cat (Richard Woods) that the hull speed is probably 7-8 knots. To get it to plane you would need to increase the speed to around 12 knots and it would require 10hp more per knot increase in speed. If I could do 5 knots on 2-3kwh of battery I would consider the project a resounding success.
 
althemusicwizard said:
Sorry I should have added, this is a power catamaran. There are no sails. Propulsion is solely via engine and in this case, the design was for two, 60HP outboard engines minimum, although if money was no object you could install a couple of 300HP outboards presuming you could afford the fuel.
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My 47ft Monohull sailboat is about 15 tonnes, and motors at 7kts with a 40hp diesel, I thinkyour weight looks low and power looks like overkill unless it's a planing hull. If you need 96v then buid the biggest 96v Lifepo4 bank you can, then build another 12v lifepo4 bank that can power all marine needs, lights refrigeration, windlass etc. you can get 230v volts for ac etc with a victron from the 12v bank
you need 96v for the motor, 12v for marine, no need to add a 48v bank.
I's recommend a diesel generator dedicated to charging batteries when the sun isn't cooperating.
 
I was just chatting with two guys who did an electric conversion to a conventional 33 ft and 36ft sloop.
One has 13 KWHR of batteries and the other about 15 KWHR. The one boat can do 19 miles and the other 25 miles on electric motor alone. This is not against or running with the wind. This is also in fairly calm water and at quite a bit less than hull speed.
That won't work for me on my 33 ft sloop. More than once I have had to motor a good part of the day (36 miles or so) to get someplace when the wind died. With 20 gallons of gas onboard, at a bit less than 1 gallon per hour, I am good for over 100 miles easy with a significant reserve for when things go sideways.

I'd probably be ok if I could jam 80-100 kwhr worth of batteries in my boat but there wouldn't be room for much else. But then there is the problem of charging all of that. I would need to be able to access a 50 amp, 240 volt power source at the dock to recharge in a reasonable time. That isn't a reasonable request at most marinas. I could carry a diesel or gas generator, but then that defeats the purpose of the electric conversion. Perhaps a fuel cell would be the answer? Someday, but not today.
 
Dave911 said:
This idea is terrible. Sailor here. Electric is ok as an aux with sails. But if you want to do more than a planned circuit route of limited range this idea is doomed. Sailboats converted to electric aux power lose value. You dont have sails.
Say you have a range if 50 miles. You leave and go 40 miles. Weather changes, storm ahead. Not enough power to get to port. No sails. No solar.
What do you do?
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run the generator
 
I had a 43” fiberglass houseboat with a planing hull. It had twin 330hp fuel injected gasoline engines. It had two fuel efficient speeds 9mph and 20mph ( comfortably,on plane). At top speed it passed everything but the fuel dock. The crazy thing is if you were moving 9mph and shut one engine off it would only drop down to 8mph.
I’ve rescued many boats or moved boats around by “side tying”, my preferred method. If it’s a short distance or tight quarters, I’ve even used my little 12 foot RIB with a 25hp efi Suzuki outboard with this method on motor yachts to 45’. With my biggest problem being visibility(tied close to stern), but maneuverability once in Harbor was an asset with such a small boat. I had no problem moving a yacht of that size up to 7 mph at 3/4 throttle unless it’s windy, then forget bout it. The most important thing that I must convey to you is prop selection. Tho that little RIB could go 32mph with just me in it, there’s no way that same prop is any good for pulling a yacht around so I always swapped it out for a bigger diameter, low pitch four blade for grunt power and less strain on the engine. I can’t overstate how important the right propeller selection is. The OP needs to consider this regarding the electric outboards. Visually, it looks like the props on those are for a runabout. Lastly, two outboards will probably be plenty. Reality, plan on a good displacement speed, otherwise the power consumption would be massive and range extremely limited.
 
One point is that 96v inverters really aren't that uncommon- at least in Australia
72v and 96v have pretty much overtaken the offgrid housing market here , with 48v being relegated to 'small bush shacks' and DIY setups lol
(indeed when I bought my own 48v, 12kw inverter- it was being sold as 'obsolete stock' at a bargain price...)
The company that made mine sells a 15kw 96v inverter as its replacement for example
And seconded on AGM being a poor choice (they are for anything these days, but buggy whip manufacturers stick with what they know lol)- good quality LFP are simply a far better choice economically and power storage versus weight/size (plus they last so much longer than any L/A chemistry battery...)
 
The first thing that I noticed between AGM’s and LFP is how easily the lithium soaks up power. With the AGM it seems that when there’s only a small amount of charge current available, nothing was being taken in. You had to have a reasonable rate of charge for it to be worth while.
 
Skypower said:
The first thing that I noticed between AGM’s and LFP is how easily the lithium soaks up power. With the AGM it seems that when there’s only a small amount of charge current available, nothing was being taken in. You had to have a reasonable rate of charge for it to be worth while.
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That is mostly due to AGMs electrolyte inefficiency- because it is literally 'soaked into a glass mat (AGM- absorbent glass mat) their 'round trip' performance effeciency and charge/discharge rates are lower than other L/A cells...
They really are a bad idea- but have gained traction because of their sealed nature ie 'fit and forget' compared to flooded L/A cells
 
I think I would consider an asymmetric solution. Use one electric outboard of your choice and one 60 HP four stroke outboard. If you are content going 7 Knots in the first place, 4 Knots won't be any worse. The 60 HP could save your bacon if you get in a jam.
 
justgary said:
I think I would consider an asymmetric solution. Use one electric outboard of your choice and one 60 HP four stroke outboard. If you are content going 7 Knots in the first place, 4 Knots won't be any worse. The 60 HP could save your bacon if you get in a jam.
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It’s a catamaran so while it will run one engine, it will run cattywampus with one engine. Two electrics and one small 4 stroke backup would probably work.
 
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