Update on Solar Conversion for 53' Trawler (32V)

[Thom Price]

So I've been living aboard the Hatteras in Baltimore for a few months now, and am starting to get my head wrapped around all of the various systems. I've had it out in the harbor a few times for short trips, but mostly I'm using it as a condo. My goal is to eventually use it for more cruising in a few years, but for now I'll be attached to shore power most of the time. I pay $0.25 per KWH for electricity here in the marina, so reducing the amount of shore power I need will both save on the electric bill when I'm "home" and reduce the need to run the generator when I'm out cruising. BTW, my background is in residential energy auditing and building small boats.
What I have:
This boat has a 32V system, which includes some lights, the three macerating heads, starter motors for the Detroit 8V-71 engines, hydraulics, and a few other items. Then there is a 120/240V AC system which includes the kitchen appliances, laundry, HVAC, water heater, some other lights, and outlets throughout. Then there is a 12V system for some of the instruments, the starter for the generator, and a few other things here and there. I have AC shore power, a 32V charger/inverter, two 32V 980AH FLA battery banks, an 8KW generator (AC), two 32V alternators, and now, as if things aren't complicated enough, I'm going to be adding solar panels.
What I've done:
Before I tackle the project of adding solar to the already complex electrical system of the big boat, I decided to start off small. I bought a wonderful little wooden dinghy that has a sail rig and rows like a dream (11" Shellback Dinghy). I mounted a 55 lb. thrust Minn Kota motor-mount electric motor on the rudder, which is powered by a 50AH Renogy LiFePo4 drop-in. It draws about 1.5 amps running wide open. I am charging that with a 100 W panel and a Renogy Wanderer charge controller. I put together a nice little ammo box that holds the battery, charge controller, a circuit breaker, volt meter, and has various outlets to connect the motor, USB charging, and 12V accessories. I also bought a little 300W pure sine wave inverter with a 12V accessory plug (for TV and anything else), a 12V charger for my laptop, and a 12V electric blanket. I haven't mounted the solar panel yet, as I am still trying to figure out where and how to do that, as well as how many other panels I'll be buying for the big system. For now, I'm just trying to figure out how much energy I can create/store/use with this little mini system.
What I'm planning on doing:
I've ordered ten 3.2V 280AH LiFePo4 cells off of Alibaba, which should get here in a month or so. I'll be replacing one of my 32V battery banks with those, while using the remaining FLA bank to provide the 980CCA needed to get the engines started when it's cold out. I'm converting the water heater (19 gal.) from AC to 32V DC by installing a 36V 1200W element (should work just fine). Once I get all of that installed, I'll keep track of my 32V system usage and size my panels accordingly. To start off with, I'll use the shore power (or generator when out cruising) for large AC appliances and the solar for all of the DC needs. Then I'll see about expanding the solar to handle the AC appliances as well. I like the idea of keeping all of these systems separated, rather than one big system.
Oh, I'm also installing a little 5KW diesel heater like they use in RVs. (5KW is the energy rating, not the electricity it uses.) I'm curious to see how it will compare to using the reverse cycle AC units (and electric space heaters) at various temperatures. I may add a second one at a later date.
That's where I am for now with the solar conversion. I'm anxious to hear people's thoughts on the project and am happy to hear about any ideas you may have.
Thanks for taking the time to read all of this.
Thom

 

[Dauntless]

Just a few observations because most on this forum know more about SP than I, but here I go.
I like your getting 10 3.2v cells. I have one 200ah 12v LiFePO battery in parallel with my SLA, since June. This hybrid system has worked extremely well and I like it. So, I would try to keep your system as simple as possible by keeping the new Lithium in parallel and only changing your charging profile.

Your diesel heater , is it forced air or hydronic? It's a good idea. Reverse cycle A/C units really are not made to be primary heaters.
For a boat your size, you will probably need two.

The only thing I'm really not sure about is your idea to convert water heater element to 32v.
Yes, it's easy to do, but water heaters take so much power. It would make more sense to me, since you are getting anew heater anyway, that you get a diesel heater that will also heat water. That would be far more efficient.
Good luck

 

[Thom Price]

Just a few observations because most on this forum know more about SP than I, but here I go.
I like your getting 10 3.2v cells. I have one 200ah 12v LiFePO battery in parallel with my SLA, since June. This hybrid system has worked extremely well and I like it. So, I would try to keep your system as simple as possible by keeping the new Lithium in parallel and only changing your charging profile.

Your diesel heater , is it forced air or hydronic? It's a good idea. Reverse cycle A/C units really are not made to be primary heaters.
For a boat your size, you will probably need two.

The only thing I'm really not sure about is your idea to convert water heater element to 32v.
Yes, it's easy to do, but water heaters take so much power. It would make more sense to me, since you are getting anew heater anyway, that you get a diesel heater that will also heat water. That would be far more efficient.
Good luck

Yes, I think having both LiFePo and SLA banks will give me the best of both worlds.
The diesel heater is forced air. I think I'll probably be adding a second one as well. The way my floor plan is, I have two engine rooms with a hallway between them that connects the galley/forward berth to the guest cabin and master state room. My plan is to have the hot air blow into the hallway of the aft cabins because I have various doors that can be opened or closed to control where the heat goes, but obviously that will be the hottest part of the boat. I'm not sure how much heat will percolate up to the salon but I'm pretty sure that very little will get up into the forward berth (not a problem as we only use it as a pantry). To encourage the heat to head in the direction of the galley and salon, I'm putting a return duct at the top of the stairs that lead from the galley to the salon, right next to the top stair. We'll see how that works. If I add a second heater, it will blow into the salon.
I've gotten a lot of comments about the water heater conversion on another forum. I understand that the water heater is a big energy hog, but there are many factors that come into play:

• The storage capacity of the water heater
• The tank insulation
• The temperature rise/set point
• The amount of hot water used

This is a 19 gal. tank to which I've added an insulation blanket. I keep it turned off most of the time, and when I turn it on, the water inside it is room temperature and I bring it up to 115F. We really don't use much hot water (also because there is a nice shower facility here at the marina). I'm looking at the water heater more as a way of storing excess energy produced by the solar panels, which we will enjoy from time to time, than I am as a source of an essential service we can't live without. For that reason, it makes sense to convert it to DC, so that more energy will go into heating the water than if it were running through an inverter. We can make adjustments to our lives so that we'll take advantage of this when there is an abundance of extra solar power. I understand that not everyone wants to live that way. It is a choice that we make and for us the cost (more limited hot water) is worth the benefit (efficiency/smaller carbon footprint).
Unfortunately, this tank doesn't have a heat exchanger in it. When it comes time to change the tank out, I'll put one of those in. Then I'll be able to scavenge heat from an engine when I'm cruising or making a harbor tour. They do make the diesel heaters that are both hydronic and forced air, and I cold look into that, but for now, I'm sticking to the simplest solution, which is to just change out an element and run a new wire to the 32V panel.
Thanks for your comments!

 

[Opusdei]

I think you should rule out the reverse cycle A/C because itt is not only x10 expensive but hard to find in the market. Your boat doesn't seem to have much roof space to go solar. I would recommend the flexible solar modules around the wall like BIPV fashion.

 

[Thom Price]

I think you should rule out the reverse cycle A/C because itt is not only x10 expensive but hard to find in the market. Your boat doesn't seem to have much roof space to go solar. I would recommend the flexible solar modules around the wall like BIPV fashion.

Interesting. I would think that at certain temperatures the reverse cycle A/C would be more efficient/less polluting than the diesel heater. I already have them, so it isn't a matter of installation cost vs. the benefit.
Also, I actually have a relatively large amount of space that could be dedicated toward PV, and it could become the hard cover of that space if I were to use rigid panels. So I'm confused by your recommendation of more expensive flexible solar panels.

 

[Opusdei]

Honestly, I have never used the reverse cycle A/C and it was just based on the power usage efficiency. Also I'm not so familiar with the space on the boat. You may disregard my recommendation about BIPV.

 

[Dauntless]

You're planning on living on the boat, right?
I think you are vastly underestimating the amount of energy you will need to just to make your living area function without feeling you are living on small boat using a cup of water to shower in and washing dishes in salt water.
People who live in Las Vegas will have excess energy with bright, sunny skies 300+ days a year. That's not your situation.
Your boat is also immersed in relatively cold water, so even on warmer days, the amount of warming that a house on land would get will be somewhat offset my the cool water bath your boat is in.

If you use little hot water, having a large water heater is inefficient. We have three of us living aboard and use about 40 gallons a day. Our 20 gallon hot water tank is just right.

Before spending time and money to reconfigure your hot water heater, live awhile and figure out your true energy budget.

 

[Maast]

I would highly recommend upsizing the 5kw diesel heater - I have one on my 30 foot aluminum pilothouse boat and it does well, but a boat of your size will need more heat - or two of the diesel heaters. You can spend the bucks and get a 12kw Planar heater which'll easily do the whole boat in the coldest weather, or you can just buy two of the cheap 5kw chinese diesel heaters and save yourself about a grand. Those cheap chinese diesel heaters work well, but they're often oversold as 8kw when they're just not.
This guy has gone into everything you could possibly ever want to know about those heaters, and he's entertaining to boot: https://www.youtube.com/user/davidmcluckie

 

[snoobler]

32V LFP + SLA paralleled as proposed = BAD IDEA!

TL;DR

You must use 11S LFP, not 10.

Before you make any decision, you need to look at your actual absorption and float voltages to confirm.

---------------------------------

3.2V * 10 = 32V nominal (LFP)
2V * 16 = 32V nominal (SLA)

That's where the similarity ends. You need to look at your charge and float voltages as well.

A common float voltage for SLA is 2.3V/cell.

2.3*16 = 36.8V SLA float
36.8V/10S = 3.68V/cell LFP = over charged.

Floating of LFP should be between 3.3 and 3.4V/cell
36.8V/11S = 3.35V

A common charge voltage for SLA is 2.4V/cell (can be higher)

2.4*16 = 38.4V
38.4V/10S = 3.84V/cell LFP = damaged battery.

38.4V/11S = 3.49V = not perfect, but definitely close to fully charged

Bottom of the range:

SLA cells empty at 1.75V/cell

16*1.75 = 28V
28V/10S = 2.8V/cell - acceptable, but you should never get anywhere near here

28V/11S = 2.55V/cell - less acceptable, but again, you should never get anywhere near here.

 

[Thom Price]

I would highly recommend upsizing the 5kw diesel heater - I have one on my 30 foot aluminum pilothouse boat and it does well, but a boat of your size will need more heat - or two of the diesel heaters. You can spend the bucks and get a 12kw Planar heater which'll easily do the whole boat in the coldest weather, or you can just buy two of the cheap 5kw chinese diesel heaters and save yourself about a grand. Those cheap chinese diesel heaters work well, but they're often oversold as 8kw when they're just not.
This guy has gone into everything you could possibly ever want to know about those heaters, and he's entertaining to boot: https://www.youtube.com/user/davidmcluckie

Yes, I think I will end up with two of them. I've been watching his youtube videos for several months now and am very entertained. I think that the 5KW vs 8KW depends on if you are counting the energy available in the fuel they burn or the heat that they produce. They don't indicate if it is input or output.

 

[Thom Price]

32V LFP + SLA paralleled as proposed = BAD IDEA!

TL;DR

You must use 11S LFP, not 10.

Before you make any decision, you need to look at your actual absorption and float voltages to confirm.

---------------------------------

3.2V * 10 = 32V nominal (LFP)
2V * 16 = 32V nominal (SLA)

That's where the similarity ends. You need to look at your charge and float voltages as well.

A common float voltage for SLA is 2.3V/cell.

2.3*16 = 36.8V SLA float
36.8V/10S = 3.68V/cell LFP = over charged.

Floating of LFP should be between 3.3 and 3.4V/cell
36.8V/11S = 3.35V

A common charge voltage for SLA is 2.4V/cell (can be higher)

2.4*16 = 38.4V
38.4V/10S = 3.84V/cell LFP = damaged battery.

38.4V/11S = 3.49V = not perfect, but definitely close to fully charged

Bottom of the range:

SLA cells empty at 1.75V/cell

16*1.75 = 28V
28V/10S = 2.8V/cell - acceptable, but you should never get anywhere near here

28V/11S = 2.55V/cell - less acceptable, but again, you should never get anywhere near here.

I have FLAs. What if I keep the two banks separated?

 

[snoobler]

I have FLAs. What if I keep the two banks separated?

In post #3, you said SLA, but I see you said FLA in #1. Ultimately, it doesn't matter.

They would need to be separated with their own charging systems. Subject the LFP to the FLA charging, and you damage them.

 

[Thom Price]

In post #3, you said SLA, but I see you said FLA in #1. Ultimately, it doesn't matter.

They would need to be separated with their own charging systems. Subject the LFP to the FLA charging, and you damage them.

Thank you so much for that insight. I will look into adding a cell to the LFP or keeping them separated. I like the idea of keeping them separated for redundancy.

 

[Smokin]

You need to check with your insurance carrier before you burn up that boat and see what they will pay after they discover the battery fire on un approved batteries.

 

[BobR]

So I've been living aboard the Hatteras in Baltimore for a few months now, and am starting to get my head wrapped around all of the various systems. I've had it out in the harbor a few times for short trips, but mostly I'm using it as a condo. My goal is to eventually use it for more cruising in a few years, but for now I'll be attached to shore power most of the time. I pay $0.25 per KWH for electricity here in the marina, so reducing the amount of shore power I need will both save on the electric bill when I'm "home" and reduce the need to run the generator when I'm out cruising. BTW, my background is in residential energy auditing and building small boats.
What I have:
This boat has a 32V system, which includes some lights, the three macerating heads, starter motors for the Detroit 8V-71 engines, hydraulics, and a few other items. Then there is a 120/240V AC system which includes the kitchen appliances, laundry, HVAC, water heater, some other lights, and outlets throughout. Then there is a 12V system for some of the instruments, the starter for the generator, and a few other things here and there. I have AC shore power, a 32V charger/inverter, two 32V 980AH FLA battery banks, an 8KW generator (AC), two 32V alternators, and now, as if things aren't complicated enough, I'm going to be adding solar panels.
What I've done:
Before I tackle the project of adding solar to the already complex electrical system of the big boat, I decided to start off small. I bought a wonderful little wooden dinghy that has a sail rig and rows like a dream (11" Shellback Dinghy). I mounted a 55 lb. thrust Minn Kota motor-mount electric motor on the rudder, which is powered by a 50AH Renogy LiFePo4 drop-in. It draws about 1.5 amps running wide open. I am charging that with a 100 W panel and a Renogy Wanderer charge controller. I put together a nice little ammo box that holds the battery, charge controller, a circuit breaker, volt meter, and has various outlets to connect the motor, USB charging, and 12V accessories. I also bought a little 300W pure sine wave inverter with a 12V accessory plug (for TV and anything else), a 12V charger for my laptop, and a 12V electric blanket. I haven't mounted the solar panel yet, as I am still trying to figure out where and how to do that, as well as how many other panels I'll be buying for the big system. For now, I'm just trying to figure out how much energy I can create/store/use with this little mini system.
What I'm planning on doing:
I've ordered ten 3.2V 280AH LiFePo4 cells off of Alibaba, which should get here in a month or so. I'll be replacing one of my 32V battery banks with those, while using the remaining FLA bank to provide the 980CCA needed to get the engines started when it's cold out. I'm converting the water heater (19 gal.) from AC to 32V DC by installing a 36V 1200W element (should work just fine). Once I get all of that installed, I'll keep track of my 32V system usage and size my panels accordingly. To start off with, I'll use the shore power (or generator when out cruising) for large AC appliances and the solar for all of the DC needs. Then I'll see about expanding the solar to handle the AC appliances as well. I like the idea of keeping all of these systems separated, rather than one big system.
Oh, I'm also installing a little 5KW diesel heater like they use in RVs. (5KW is the energy rating, not the electricity it uses.) I'm curious to see how it will compare to using the reverse cycle AC units (and electric space heaters) at various temperatures. I may add a second one at a later date.
That's where I am for now with the solar conversion. I'm anxious to hear people's thoughts on the project and am happy to hear about any ideas you may have.
Thanks for taking the time to read all of this.
Thom

Edit: just noticed this is an old thread that had a new post that brought it up to 'whats new'.
re: your little boat (your dinghy didn't sound right).
I am putting together a 10 ft. dinghy using a 55#Minn Kota lower unit and am wondering what your top speed is.
You said 1.5 amps at full speed are you achieving hull speed with that?
I think your Shellback has a LWL of about 10ft so your hull speed should be about 4.8 mph.
Thanks