looking for a design overview input

[Goboatingnow]

I would suggest 20-30 metres of thruster compatible cabling is going to be a hell of lot cheaper then your proposed battery system. More reliable and easy to maintain

I'm not sure you recognize the scale of what you are proposing, or that you've done any math. The 100kWh battery you propose will take 20 hours to charge with your generator. Usually people size a generator to charge a bank in an hour or so.

You are not the only person with a 70 ft. cat. And most are in the tropics. I seriously doubt even a single one has the battery and A/C load you propose.

Maybe bounce over to cruisersforum.com where others with a similar sized boat can offer solutions. I spent several years in the tropics on a boat, fwiw. Your time and money will probably be better spent on good insulation and window shades. A shade tent outside can counter the effects of a dark hull. Might be hard on a cat but many monos use them. 3 tons of AC will handle 2000 sf. That would be more than plenty for your 1000 sf in the tropics, especially if you close off unoccupied areas.

Anyway, at cruisersforum you will probably find help from others that have a similar boat and already engineered a working system.

be careful looking at other peoples installs. Lithium Practice , equipment selection and standards are evolving. Also so is general knowledge. Many existing installs are now outdated , potentially borderline safe and use out of date concepts.

 

[Skypower]

For us to better understand it would be good to know what wiring infrastructure already exists for the best economics. Distance from power source, battery location, loads (thrusters). I only have two concerns. Make sure your alternators can handle the load that lithiums can pull, considerably more than a comparable ah AGM it may replace. If the alternators have thermal limiting features you may be ok. I’ve seen upgraded alternators actually stall small propulsion engines if the load can’t be dialed back for low rpm maneuvering (some high end marine alternators have this feature) but I don’t suspect that as a problem with your setup. The second issue is the use of DIY lithium battery banks. I don’t believe the ABYC has any strong issue against it, but be warned that marine insurance providers are notoriously known for denying claims for anything not USCG approved, even if it’s not a related system failure or passed/missed by a marine survey. But they’d be happy to take your money till there’s a problem. Most marine insurance companies are crooks. Luckily I’ve never had a claim. One suggestion on your solar is to break up the system into as many charge controllers as possible while also maintaining as close to the max open circuit voltage for each charge control. That way if a shadow is cast on one part (mast, antenna) you don’t loose all the potential energy of the rest. Stick to those little Victons, they start charging very early and are amazingly efficient. Your air conditioning system is huge! I installed a 16kbtu MarineAir on a 43’ 1978 fiberglass houseboat. Only had 1-1/2 insulation in the roof and small air space in the walls and single pane windows, yet it cool the whole boat on a 102* day. Very quiet at night. I’ve been seeing people hanging these split system on their boats because they are insanely efficient but those were the home types. Don’t know how well they’d hold up to salt spay and the outside noise when you just want to sit on your deck for a peaceful evening.

 

[sandog]

Sat down and did an estimated energy audit. It comes in at 65.2kwh/day with no AC, with AC 161.4kwh/day.

So the 100kwh house bank is appropriately size

The alternators on the engines I plan to charge the AGM's and hope to come up with a solution for the AGMs to apply power into the house bank. Any thoughts?

Moving thruster cables to a central battery bank is not economical. After pricing wiring, it would be about $7k just in wire. Not to mention trying to maneuver that wire would be less than a fun time.

 

[sandog]

For us to better understand it would be good to know what wiring infrastructure already exists for the best economics. Distance from power source, battery location, loads (thrusters). I only have two concerns. Make sure your alternators can handle the load that lithiums can pull, considerably more than a comparable ah AGM it may replace. If the alternators have thermal limiting features you may be ok. I’ve seen upgraded alternators actually stall small propulsion engines if the load can’t be dialed back for low rpm maneuvering (some high end marine alternators have this feature) but I don’t suspect that as a problem with your setup. The second issue is the use of DIY lithium battery banks. I don’t believe the ABYC has any strong issue against it, but be warned that marine insurance providers are notoriously known for denying claims for anything not USCG approved, even if it’s not a related system failure or passed/missed by a marine survey. But they’d be happy to take your money till there’s a problem. Most marine insurance companies are crooks. Luckily I’ve never had a claim. One suggestion on your solar is to break up the system into as many charge controllers as possible while also maintaining as close to the max open circuit voltage for each charge control. That way if a shadow is cast on one part (mast, antenna) you don’t loose all the potential energy of the rest. Stick to those little Victons, they start charging very early and are amazingly efficient. Your air conditioning system is huge! I installed a 16kbtu MarineAir on a 43’ 1978 fiberglass houseboat. Only had 1-1/2 insulation in the roof and small air space in the walls and single pane windows, yet it cool the whole boat on a 102* day. Very quiet at night. I’ve been seeing people hanging these split system on their boats because they are insanely efficient but those were the home types. Don’t know how well they’d hold up to salt spay and the outside noise when you just want to sit on your deck for a peaceful evening.

Solar system I did want to break up into 4~ 5 strings.

I understand the AC system is huge, but 3 different firms came up with close to the same tonnage. Some used all in ones, some came up with a chiller/air handler combo.

Batteries, I may just go with 100kwh of rack mounts to make life simpler

 

[sandog]

I'm not sure you recognize the scale of what you are proposing, or that you've done any math. The 100kWh battery you propose will take 20 hours to charge with your generator. Usually people size a generator to charge a bank in an hour or so.

You are not the only person with a 70 ft. cat. And most are in the tropics. I seriously doubt even a single one has the battery and A/C load you propose.

Maybe bounce over to cruisersforum.com where others with a similar sized boat can offer solutions. I spent several years in the tropics on a boat, fwiw. Your time and money will probably be better spent on good insulation and window shades. A shade tent outside can counter the effects of a dark hull. Might be hard on a cat but many monos use them. 3 tons of AC will handle 2000 sf. That would be more than plenty for your 1000 sf in the tropics, especially if you close off unoccupied areas.

Anyway, at cruisersforum you will probably find help from others that have a similar boat and already engineered a working

It is why my system has two generators. One 5kw and one 33kw. Coupel in with 8~9kw of solar and about 65kw of energy off the alternators daily.

For the AC, again, 3 different design firms came up with this. I thought it was excessive as well. But my 52' boat, with substantially less interior volume was designed and installed by Hinckley, and is 80k BTU. I am adding about twice as much interior space but only increasing AC by 50% more.

 

[sandog]

If you are looking at a battery that size, and 10 tons of A/C, you can't consider saving a few bucks to reuse crappy alternators or trying to save money on wire.

Put some energy into what the BMSs will be. Budget $15,000 for all the BMS and control equipment, don't be surprised if it goes over that, and don't stress the money for wire and few hundred for external regulators.

I really suggest you need to reconsider the size of batteries, size of A/C, and work up a complete and proper energy budget.

And changing out alternators is not really cheaping out. Adding in balmars, new brackets and wakespeed charge controls is approaching 8~9k. If it was a few hundred, or even a grand or two, I would be all for it.

 

[sandog]

I would suggest 20-30 metres of thruster compatible cabling is going to be a hell of lot cheaper then your proposed battery system. More reliable and easy to maintain too.

This design needs significant rationalisation. The configuration is not technically justifiable nor based on sound principles , you are wasting money also.

Rationalise and simplify it. One big AGM bank will happily support your AGM demands.

Have one boat system voltage

Then you need to do a inch by inch design review looking at cabling size , fuses , manual overrides safety review, and ABYC and or ISO suggested practices.

I would love to have one voltage system. But again, chaing out bow thrusters to 12v, or changing out engine controls and systems to handle 24v, is not necessarily easy, nor inexpensively done.

 

[Goboatingnow]

I would love to have one voltage system. But again, chaing out bow thrusters to 12v, or changing out engine controls and systems to handle 24v, is not necessarily easy, nor inexpensively done.

Sure but compared to the OPs very expensive multi battery multi voltage of simplify things.

 

[sandog]

Thank you for your input everyone. I sat down with a Victron Premier distributor yesterday. The biggest thing I now need to redesign is the inverter. I need to go to the multiplus 5kw one and parallel 4 of them, or 6 of the 3kw units.