Sailing Catamaran Power

El Guapo

New Member
Joined
Jan 7, 2021
Messages
13
Hello,

My family and I recently purchased a sailing catamaran and we are experiencing challenges with power generation/storage and are hoping to find some help.

Here are the existing system specs:
6 - 6v 220ah batteries (I don't know how to test battery capacity/efficiency but am growing increasingly concerned that the batteries were not well cared for or the two years of non-use has drastically reduced the useful life. )
2 - 140 watt solar pv panels
4 - 100 watt solar pv panels

I just installed a new 170a Balmar on my stbd eng and this has proven to be the one thing that keeps us going as the solar panels aren't charging/keep up with our demand. I understand the pros/cons of lithium and have determined that I don't want the fire hazard on board. Zinc-ion doesn't seem to be an option yet so I may have to stay with AGMs?

I completed the attached energy audit but it seems really high to me.

I was thinking about bringing the house battery bank and solar pv input up to around 1100-1200 watts, keeping the Balmar on a single engine, and adding hydro/wind generation capacity hoping this will round out the system.

Based on the attached audit and the above description, does anyone have any feedback? Anything I have not considered but need to? How can I test if my existing batteries are good and is there a way to add the additional +/- 600 watts that I want to add without replacing all batteries? (or if the batteries are bad, I will likely go with 6 - 6v 400ah AGMs unless someone has a different solution).

I appreciate any help/input.

Kindly,

Kevin Fort
s/v Blue Shadows
www.blueshadowsadventures.com
 

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snoobler

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Welcome to the forum.

LFP is no more dangerous than AGM.

You only only 4kWh of usable battery capacity (50% of rated), which is pretty anemic.

It is really high because it is. 6 hours of A/C and three hours of a water maker is VERY demanding - those two items alone are 11kWh - over half your load.

If your goal is to power everything with solar, you need the calculated 4800W. You'll also need a lot of expensive solar charge controllers = about $2500-3000 worth.

Regardless of source, you've established that you need 20kWh of energy daily. That's 10 hours on the Balmar.

You might be getting 3.4kWh from your existing panels provided they are configured correctly and shading is not an issue.

Tiny wind turbines you see on boats (not the 6-7' diameter turbines) produce very little power even in decent winds. Let's say 100W for 12h/day. that's another 1.2kWh.

Not sure what you get with hydro, but you have a big gap between 20kWh and 4.6kWh you get with solar/wind. Assuming nothing from hydro, 15.4kWh will need 7.5 hours of Balmar running to supply all loads. This also assumes that you produce the power at the right times and have suitable storage.

12V is also very challenging at these demand levels... currents are VERY high.

It might help to separate out the high load things from the low load items, i.e., Water heater, A/C and Water Maker all require you to run the Balmar. If you take all those things out, you only need 7.5kWh/day - a little over 1/3 the total need, and you're almost half way there already with wind and solar.
 

Diysolar123

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Feb 28, 2021
Messages
646
you could try and just test your batteries using an internal resistance tester/analyzer...they are not that expensive and give a good hint as to the health of the little critter.
these are less than $100 on ebay (SM8124A Portable Battery Internal Resistance), obviously not "laboratory grade" gear here but it should provide a hint hehe
 

newbostonconst

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Sep 24, 2019
Messages
624
LifePo4 is safe and no acid/maintance to deal with.

It is to bad there isn't an easy way to take the heat from the AC and make hot water....

I don't see how you are going to get to your goal even if you covered every inch of the boat with solar. You need to do a major cut back, limit computers, AC, water.....

How many people do you have on the boat? Are you Bluewater sailing 24/7 all year around?

Wish you luck and we hope to be where you are some day soon....
 

El Guapo

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Jan 7, 2021
Messages
13
Snoobler - thank you. your reply was very helpful and pointed me in the right direction for continuing my research.

Diysolar123 - Thank you, that tool may prove useful.

newbostonconst - I agree, it would be really neat to convert a/c heat to hot water. My diesel engines do this now but it is not efficient or environmentally friendly. We are a full-time bluewater cruising family and spend 365 days/year on the boat. My wife and I run our business from the boat. Most of the time, it is just my wife, our 7 year old son, and myself on board. Occasionally, we will have 2-4 additional guests for a couple of weeks at a time.

I did a lot of reading last night and am feeling more curious and open the LFP. I am also starting to think that I should seriously consider a 24v conversion of my house bank. While I don't want to say money is not an issue, I am in a position to make a reasonable investment to try and get our power generation and storage capacity closer to our consumption.

I do think there are some opportunities to cut back on consumption but I'm still really surprised by how high the numbers came in on the audit. I estimated "high" on usage hours to try and provide a buffer but even still, it seems incredibly high for what I feel is an actual amount of usage. Being new to cruising, perhaps we still need to shake our "landlubber" electrical usage habits and learn "cruising" electrical usage habits...

I just bought a brand new Freedom XC 2000w inverter and Outback Flexmax 80a controller. The Outback would be usable on a 24v system but it looks like I would have to find a different inverter/charger to replace the XC 2000 if I convert to a 24v system. I will also have to see if my Balmar would still be usable.

I'm thinking we might nurse our current system as we sail from Northeast FL to Maine and spend the winter months in Maine designing and installing a proper 24v LFP system and try to bring my ah up to as close to 1100-1300 as possible on both the battery bank and solar. As I have come back to many times, wind generation on a boat just seems inefficient and noisy. I like the idea of hydro generation but I would prefer to look at a full conversion to electric motors that combine hydro-generation. That is a $60k upgrade to the boat however.

If you guys have any thoughts you feel are important for consideration with the 24v conversion, I greatly appreciate your time!

All my best,
 

newbostonconst

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Sep 24, 2019
Messages
624
You will have no money lost in batteries because they can be configured to any voltage and the Flexmax is a good choice for charge controllers and flexible. You could always keep the 2000 watt inverter as a backup.

You will need a DC to DC inverter to still run your 12 volt stuff if you go to 24 volts or higher. Not sure in your situation is worth the upgrade. The Flexmax will more efficient at the higher voltage you go but not ground breakingly. I do think if you made the jump to go higher voltage, I would just go right to 48 volts or even closer to 60 volts. 2/3rds of your usage is in AC so that is good.

What if you kept a small 12 volt system plus a 48 volt AC system? Is that a option on the boat as far as wiring and equipment placement?
 

snoobler

Solar Honey Badger
Joined
Jul 10, 2020
Messages
8,430
Location
HBR, AZ
Snoobler - thank you. your reply was very helpful and pointed me in the right direction for continuing my research.

Diysolar123 - Thank you, that tool may prove useful.

newbostonconst - I agree, it would be really neat to convert a/c heat to hot water. My diesel engines do this now but it is not efficient or environmentally friendly. We are a full-time bluewater cruising family and spend 365 days/year on the boat. My wife and I run our business from the boat. Most of the time, it is just my wife, our 7 year old son, and myself on board. Occasionally, we will have 2-4 additional guests for a couple of weeks at a time.

Long term guests that are not power usage conscious can make even conservative estimates insufficient.

I did a lot of reading last night and am feeling more curious and open the LFP. I am also starting to think that I should seriously consider a 24v conversion of my house bank. While I don't want to say money is not an issue, I am in a position to make a reasonable investment to try and get our power generation and storage capacity closer to our consumption.

24V would be more optimal when considering AC wattage, and it would cut your MPPT charge current requirements allowing your FM 80 to handle about 2000W of solar.

I do think there are some opportunities to cut back on consumption but I'm still really surprised by how high the numbers came in on the audit. I estimated "high" on usage hours to try and provide a buffer but even still, it seems incredibly high for what I feel is an actual amount of usage. Being new to cruising, perhaps we still need to shake our "landlubber" electrical usage habits and learn "cruising" electrical usage habits...

Yep. piggy-backing on propulsive power is a tiny load (about 3hp) on the engines and very efficient. Running the engines just to produce electricity is very inefficient.

I just bought a brand new Freedom XC 2000w inverter and Outback Flexmax 80a controller. The Outback would be usable on a 24v system but it looks like I would have to find a different inverter/charger to replace the XC 2000 if I convert to a 24v system. I will also have to see if my Balmar would still be usable.

Correct. A 24V inverter/charger would be required. You would need one or more 12-24V converter(s) to be able to charge 24V from 12V charging sources. I presume you have the ability to connect to shore power. An inverter/charger would permit battery charging from shore power.

If your inverted 120VAC peak power is under 3000W, you can probably stick with 12V to avoid the hassle of

I'm thinking we might nurse our current system as we sail from Northeast FL to Maine and spend the winter months in Maine designing and installing a proper 24v LFP system and try to bring my ah up to as close to 1100-1300 as possible on both the battery bank and solar. As I have come back to many times, wind generation on a boat just seems inefficient and noisy. I like the idea of hydro generation but I would prefer to look at a full conversion to electric motors that combine hydro-generation. That is a $60k upgrade to the boat however.

Given that Balmar can power your needs, that sounds like a good plan. 28kWh of LFP would run you about $4000 if you DIY the batteries.

I've seen purpose-built all-electric boats that are great... if you don't need to go far or fast, and have space for a massive solar array. $60K seems like a very low price.

Additionally, the idea of an electric motor combined with hydro seems counterproductive, i.e., you're using electricity to power a motor to move the boat and then run a hydro generator. Ultimately, you will lose more than you gain, i.e., the electrical energy generated by the hydro will be less than the extra energy the motors use to overcome the additional drag of the hydro generator... almost like strapping an alternator on an electric motor. The only way it makes sense is alternator/hydro is also converting to a lower voltage.
 

El Guapo

New Member
Joined
Jan 7, 2021
Messages
13
You will have no money lost in batteries because they can be configured to any voltage and the Flexmax is a good choice for charge controllers and flexible. You could always keep the 2000 watt inverter as a backup.

You will need a DC to DC inverter to still run your 12 volt stuff if you go to 24 volts or higher. Not sure in your situation is worth the upgrade. The Flexmax will more efficient at the higher voltage you go but not ground breakingly. I do think if you made the jump to go higher voltage, I would just go right to 48 volts or even closer to 60 volts. 2/3rds of your usage is in AC so that is good.

What if you kept a small 12 volt system plus a 48 volt AC system? Is that a option on the boat as far as wiring and equipment placement?
I believe it would be possible. I have plenty of storage space available.
 

rin67630

Solar Addict
Joined
Apr 29, 2020
Messages
810
Agreed. Mentioned to qualify the claim.
Solar on sailing boats has its own rules: you should always make symmetrical constructions of panel pairs backboard and starboard in parallel in order to have one panel irradiated while the other one is shaded by the sails.
Also consider the general installed solar power to be only ~30% of the label power, since one half is under shade and the other half has a bad slope.
You are mainly constrained to small panels of the 100W class with 18Vmpp, so 24V batteries are practically not feasible.
A plain PWM SCC is usually the best choice, considering the low voltage difference between Vmp and the battery voltage.
PWM has also a ways better ability to recover from the inevitable frequent shades for seconds due to your activity on the boat.
 
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