Need Help connecting new electric saildrives to existing solar house bank

[teecomp]

Hello. Newbie here with limited solar understanding/knowledge who would greatly appreciate ideas with tying new saildrives into my sailboat's existing solar system for the house bank. I bought the boat (catamaran) in June and just re powered with two 20 KW saildrives from Electric yacht. Each saildrive is powered by 8 six volt agm lifeline batteries 300ah. Each engine has a DeltaQ 48V 25A charger for it's bank which plugs into receptacles of the AC system fed by either shore power or the onboard 6kw diesel generator. The boat has an existing solar bank of 685 watts from eight panels with a RV power products Solar boost 50 mppt 12/24v 50 amp controller. The house bank has 6 agm 6volt 220ah wired 2s3p 12V, North Star 12/1200 inverter, Mastervolt charge master 12/70/3.
My wife, daughter, and myself hope to live aboard in about a year so I would like to rely on the generator as little as possible and get the maxium use of my solar. I have no idea of the wattage or voltage of the panels (boat listing by the broker stated 685w but that seems low for 8 panels -roughly 2'x4' each). Since I have a 12v dc house system and now, 48V electric saildrives, I would appreciate any suggestions on the best way to incorporate the three battery banks together for solar charging. I am planning on upgrading some, if not all, of the panels to get the most wattage for the space I have. Would it be better/cheaper/mandatory to split the panels into seperate banks for the motors and the house banks? Thanks!

 

[Q-Dog]

100 watt panels available today are approximately 26" X 40" give or take a couple inches, so 685 watts sounds about right. I suspect your current solar setup barely keeps the house batteries charged up.

 

[EndlessPlaytime]

I think you need to make a power budget and look at how long it would take your solar to charge all those batteries. You have 36,000Wh of battery and only 685W of solar. Each device you use to move power around has some efficiency % and wastes power.

So you probably need a lot more solar and hook it up to your 48V banks if you want to liveaboard and not rely on shore power or generator.

It's easier to focus your charging efforts on the higher voltage 48V battery bank and then use a DC-DC converter to power 12V loads and charge a smaller 12V house bank. To do this you'd need to get a new 48V solar controller and make sure your solar panels are wired in series to output at least 48V. Then you also need a 48 to 12V DC-DC converter.

*Not recomending*!. With minimal changes, you could technically plug your 48V chargers into your inverter and limit your 48V charging current to stay under the 12V inverter power limit. This would then charge all your battery banks from solar. However, it'll mostly just make heat, waste power and kill your house bank. *Not recomending*

 

[Abelungu]

Hello. Newbie here with limited solar understanding/knowledge who would greatly appreciate ideas with tying new saildrives into my sailboat's existing solar system for the house bank. I bought the boat (catamaran) in June and just re powered with two 20 KW saildrives from Electric yacht. Each saildrive is powered by 8 six volt agm lifeline batteries 300ah. Each engine has a DeltaQ 48V 25A charger for it's bank which plugs into receptacles of the AC system fed by either shore power or the onboard 6kw diesel generator. The boat has an existing solar bank of 685 watts from eight panels with a RV power products Solar boost 50 mppt 12/24v 50 amp controller. The house bank has 6 agm 6volt 220ah wired 2s3p 12V, North Star 12/1200 inverter, Mastervolt charge master 12/70/3.
My wife, daughter, and myself hope to live aboard in about a year so I would like to rely on the generator as little as possible and get the maxium use of my solar. I have no idea of the wattage or voltage of the panels (boat listing by the broker stated 685w but that seems low for 8 panels -roughly 2'x4' each). Since I have a 12v dc house system and now, 48V electric saildrives, I would appreciate any suggestions on the best way to incorporate the three battery banks together for solar charging. I am planning on upgrading some, if not all, of the panels to get the most wattage for the space I have. Would it be better/cheaper/mandatory to split the panels into seperate banks for the motors and the house banks? Thanks!

Boating has one golden rule “there are never enough power” 2nd rule is maximize your real estate. That being said, your focus should be on your solar abilities. That means you work from the top down. I your case you need to work from the bottom up. I live in Florida and my most valuable commodity is AIR CONDITIONING and REFRIGERATION.(I build marine HVAC equipment and will build my own) Seeing that you live on the boat your comfort is essential for you and your family. I have been living on board for close to 25 years. Remember when you are under way is fraction of the time you spend on board. In your case sailing is a big help for not relying on fossils. Design your system so you can satisfy refrigeration and air conditions for a preriod of 9 hours completely from your batteries (night time). If you look at my posts you will see that people have broken down the math on a project like mine very simply and effectively. BUT I have 6000 watt of solar that’s going up. See the difference? I have been restoring boats and building custom MARINE HVAC EQUIPMENT for many years. As boaters we all need help, all the time. I need to see a photo of your boat, maybe I can help?‍

 

[RobBob]

Boating has one golden rule “there are never enough power” 2nd rule is maximize your real estate. That being said, your focus should be on your solar abilities. That means you work from the top down. I your case you need to work from the bottom up. I live in Florida and my most valuable commodity is AIR CONDITIONING and REFRIGERATION.(I build marine HVAC equipment and will build my own) Seeing that you live on the boat your comfort is essential for you and your family. I have been living on board for close to 25 years. Remember when you are under way is fraction of the time you spend on board. In your case sailing is a big help for not relying on fossils. Design your system so you can satisfy refrigeration and air conditions for a preriod of 9 hours completely from your batteries (night time). If you look at my posts you will see that people have broken down the math on a project like mine very simply and effectively. BUT I have 6000 watt of solar that’s going up. See the difference? I have been restoring boats and building custom MARINE HVAC EQUIPMENT for many years. As boaters we all need help, all the time. I need to see a photo of your boat, maybe I can help?‍

I'm trying to design my system around 7000 watts of solar.

My goal is to insulate everything and enclose the main cabin and rooms. Seal all the windows and build my own AC system. My problem is trying to find everything at 48v. In order to be as efficient as possible all the high draw stuff I'm trying to make 48v which is what my main battery packs are at.

I could get away with using some 12v blower motors that don't have high draws but finding 48v compressor motors and heating elements is rough.

Any suggestions would be appreciated.