A question probably asked, so pardon me if I repeat it.

[LoudMusic]

Originally Posted by CatNewBee

Do not want to post everything twice, but you can lookup my thread 1000Ah LiFeYPO4 and all electric galley. Its a Lagoon 400S2 40ft catamaran with large solar array.

Bottom line it is somehow doable to run fridges, freezer, electronics and the waterheater out of solar only when the sun is shining and recharge what you consumed during the night before whithout needing dino juice.

If you not run the water heater, you may run either the watermaker or a washing machine or one A/C unit for some time ( 1..2h ) to cool down one cabin before sleeping and get the energy recharged by solar. On good days youbwill have probably excess energy from 2pm to sunset, what you can invest in A/C or other stuff. One A/C unit can be run off the solar array alone, but you have other loads that need power too, so the battery will drain slowly.

You can save 120Ah/day if you are contious about energy saving and turn off the inverter when not needed. See the details in my thread.

I also have a 7kW generator on board, if I need more than my LFP can provide, the battery can be recharged with up to 350A with all I have (2x 40A legacy charger, 220A nominal Victron Quattro charger - delivers 180..200A, 100A solar), so in best case the battery is full again from empty in 2.5...3h, having 2-3kW extra juice for A/C, hot water, watermaker, washing machine or galley during the charging.

If you are savvy and not use everything everyday, solar only will work for a long time. I tested it for 2 weeks without any other power source inclusive cooking and baking in the galley and running all fridges / freezer on the coldest setting, but you cannot run A/C all day long then.

I'm sitting on 900Ah of LFP and 700w of solar. I think I'd double my LFP and triple my solar to be able to run one 10,000 BTU aircon through the night.

Now to find that sunken treasure to make all my dreams come true ...

[john61ct]

Originally Posted by LoudMusic

I'm sitting on 900Ah of LFP and 700w of solar. I think I'd double my LFP and triple my solar to be able to run one 10,000 BTU aircon through the night.

Now to find that sunken treasure to make all my dreams come true ...

Still not enough in the tropics.

Unless **very** well insulated

[ramblinrod]

Yes it is possible if one has the real estate for the infrastructure.

Step 1. Determine if you really need all of the convenience and comforts of
Land living, when on the water.

Step 2. Determine the power generation and storage capacity to support your intended loads.

Step 3. Determine the infrastructure required to support it.

Step 4. Estimate costs and proceed or go back to step 1.

Seriously, if you don’t know the answer to this kind of question, you should consult
an expert in Marine electrical systems. It will save you a whole lot of time, effort, and most likely money if you value value your research/learning time, and mistakes made due to lack of experience.

[CatNewBee]

Originally Posted by ramblinrod

Yes it is possible if one has the real estate for the infrastructure.

Step 1. Determine if you really need all of the convenience and comforts of
Land living, when on the water.

Step 2. Determine the power generation and storage capacity to support your intended loads.

Step 3. Determine the infrastructure required to support it.

Step 4. Estimate costs and proceed or go back to step 1.

Seriously, if you don’t know the answer to this kind of question, you should consult
an expert in Marine electrical systems. It will save you a whole lot of time, effort, and most likely money if you value value your research/learning time, and mistakes made due to lack of experience.

On the L400S2 there are 4 A/C units with 44000 btu in total. you can run one unit (10000 btu) on solar with 1650Wp panels if you have nothing else running.

[john61ct]

And then you need an additional power source to recharge your battery bank for all the other gear on your boat.

So step 0 is start with a boat with hundreds of square feet of free flat area to mount panels, that won't interfere with the boat's operations.

And don't mind how that looks.

[CatNewBee]

Any device, that produces heat or removes heat is a power hog.

So chose what you really need running.

[wallythacker]

So my 4x200ah AGM bank (all 12v batteries for ease of math) which provide 400a@12v for 20hrs (mfg. rating) will provide 50a@12vdc for about 8 hrs?

I read that half the rated capacity should be used for calculations.

My 5600btu AC requires about 5a@120vac or 50a@12vdc. Will I get about the 8 hours that I calculate the bank can provide? How much loss is there converting my DC bank to AC in the inverter?

Am I anywhere remotely close with my calculations or off by miles?

As for charging the bank back up i have room on my boat for 12 standard size solar panels without resorting to hinging them on the rails. Figuring on charging the bank up will come later.

[john61ct]

I am so confused

Originally Posted by wallythacker

So my 4x200ah AGM bank (all 12v batteries for ease of math) which provide 400a@12v for 20hrs (mfg. rating) will provide 50a@12vdc for about 8 hrs?

State what the batteries are, not obfuscating to make the math "easier".

If 4 x 12V batts, each 200AH makes 800AH.

If 6V, and each 12V pair is 200AH, then 2 pair is 400AH.

Assuming the latter, if the mfg spec is the 20-hour rate - some use the 10-hour one - that 400AH means steady 20A rate draw from 100% Full for 20 hours will bring it down to 10.5V 0% empty.

This will not translate linearly to other rates / durations because of Peukert's Law.

____
As to the rest, no, you cannot afford to run aircon off batteries for any length of time.

You will need a generator, batteries will only allow a little timeshifting.

Maybe 1200W of solar will run a tiny aircon during peak sunshine, but nothing is left to recharge the bank.

You only need aircon while parked at the marina, and of course shore power works best.

[wallythacker]

I didn't think it was a linear discharge. Where do I look for the discharge graph? Battery mfg? seems logical.

See, with my choice of 12v batteries you nearly got it wrong.

I think it's pretty clear that the proposed bank is only 4 batteries. There's no space for more. Since only 4 batteries will fit 12v batteries are chosen over 6. Each battery is rated at 200ah/20hr according to the mfg. How can I be any clearer in stating what they are? Listing the number of cells each battery has? How?

Then I add that reading has told me to take HALF the capacity of the batteries in calculating my total power available. (no link for that recommendation.)

Anyway, I'm almost retyping my original post verbatim so what's the point in that? I'll stop now

Tell you what, since I'm planning on installing this power plant on my boat (power plant to me is the combination of batteries, solar panels, wind gen and boat generator) anyway once it's up and running I'll experiment and see how long my AC in the master cabin will run away from the dock.

And I'll report back.

Someone here posted that a family, the Wynns have done this, their power plant doesn't need shore or gennie power to exist.

[john61ct]

Originally Posted by wallythacker

I didn't think it was a linear discharge. Where do I look for the discharge graph? Battery mfg? seems logical.

Not sure what exact data you mean, nor why you think you need it. Maybe specify what units on each axis?

> I think it's pretty clear that the proposed bank is only 4 batteries. There's no space for more. Since only 4 batteries will fit 12v batteries are chosen over 6. Each battery is rated at 200ah/20hr according to the mfg.

Link to the model?

So, 800AH.


> I add that reading has told me to take HALF the capacity of the batteries in calculating my total power available.

Yes if lead, 400AH usable storage.

> Someone here posted that a family, the Wynns have done this, their power plant doesn't need shore or gennie power to exist.

The Wynns are not technical experts, and have had hundreds of thousands' worth of gear donated by sponsors.

In a very small well insulated space a 5k BTU unit will it is true cycle on and off.

But replenishing what you use per hour (x1.25) will require a lot more power than you get from alternative energy except in perhaps optimal conditions.

That issue is completely independent of your bank's storage capacity.

I assume your boat will also have other electrical load consumers?

[Jammer]

Originally Posted by wallythacker

Is it possible to install enough solar and wind using today's tech to run a watermaker part time, say, 10% of the day? along with running a 16.5k btu AC unit 50% of the day, run the fridge and normal devices and maintain a neutral balance on the battery bank?

Not with the air conditioner. Take out the air conditioner, then you can do it.

[Jammer]

Originally Posted by wallythacker

I didn't think it was a linear discharge. Where do I look for the discharge graph? Battery mfg? seems logical.

See, with my choice of 12v batteries you nearly got it wrong.

I think it's pretty clear that the proposed bank is only 4 batteries. There's no space for more. Since only 4 batteries will fit 12v batteries are chosen over 6. Each battery is rated at 200ah/20hr according to the mfg. How can I be any clearer in stating what they are? Listing the number of cells each battery has? How?

200ah at the 20 hour rate means you can get 10 amps for 20 hours. 10a * 20h = 200 ah.

With 4 12v batteries, you would get 40 amps for 20 hours, at 12v.

At 120v, you would get somewhat less than 4 amps, for 20 hours.

Then I add that reading has told me to take HALF the capacity of the batteries in calculating my total power available. (no link for that recommendation.)

Good advice for many reasons

I'll experiment and see how long my AC in the master cabin will run away from the dock.

A 16.5kbtu/h air conditioner will draw approximately 15 amps at 120 volts. The actual draw will vary somewhat depending on weather conditions and the temperature and humidity in the cabin. If you measure, you will observe that it draws somewhat more on hot days when the cabin is hot, than on cooler days. ..shrug.. The difference is small, maybe 12 amps one day, 16 amps the next.


Anyway, at 15 amps at 120 volts, you would draw, through an inverter, approximately 150 amps at 12 volts. With a bank of four 12v batteries that are rated at 200 amp-hours at the 20 hour rate, you will be able to operate the air conditioner for approximately four hours, with no other loads. The batteries will not be able to deliver their full useful capacity into a load that large.

Weight and space limit how much battery capacity you install. Much of the reason people use LiFePO batteries is that they have a higher power density and allow more power storage in the space and weight limits that govern.

The amount of space available for solar panels governs your ability to generate power. Clouds, shadows, inability to tilt the panels toward the sun, all reduce output. How much solar you have room for depends on your boat and on what you will give up in terms of windage, appearance, and useful space. A full size 300w panel will maybe give you 100 a-h of useful battery charging on an average day in the tropics. If you had 8 panels then you could recharge your batteries on an average day. Very few boats have that kind of room. The full size panels are approximately 3' x 6' each.


Wind generators have fallen out of favor but are still sometimes used to augment solar power in areas prone to windy days with no sun. Typical output, who knows, maybe 50 a-h of useful battery charging on an average day.


Hope this helps.

[john61ct]

Noise / vibration of wind genny drives me nuts personally.

OP are you inspired by environmental motivations to avoid fossil fuel power generation, or cost, or what?

[a64pilot]

You can do it, with a houseboat, about 4 KW of Solar and LFP batteries, assuming your not trying to keep the temp at 68 or something, if you are your going to need very efficient insulation and likely no windows.

[mitiempo]

Originally Posted by Jammer

200ah at the 20 hour rate means you can get 10 amps for 20 hours. 10a * 20h = 200 ah.

With 4 12v batteries, you would get 40 amps for 20 hours, at 12v.

At 120v, you would get somewhat less than 4 amps, for 20 hours.



Good advice for many reasons



A 16.5kbtu/h air conditioner will draw approximately 15 amps at 120 volts. The actual draw will vary somewhat depending on weather conditions and the temperature and humidity in the cabin. If you measure, you will observe that it draws somewhat more on hot days when the cabin is hot, than on cooler days. ..shrug.. The difference is small, maybe 12 amps one day, 16 amps the next.


Anyway, at 15 amps at 120 volts, you would draw, through an inverter, approximately 150 amps at 12 volts. With a bank of four 12v batteries that are rated at 200 amp-hours at the 20 hour rate, you will be able to operate the air conditioner for approximately four hours, with no other loads. The batteries will not be able to deliver their full useful capacity into a load that large.

40 amps for 20 hours from a 800AH bank is impossible. The A/C would shut down well before the time was up. Batteries are measured for a 20 hour draw to 10.5 volts. Do that a few times and you can throw the batteries away. 10 hours @ 40 amp draw takes the bank down to about 50% (12.1 volts approx.) That is as far as you want to go if you want the batteries to last very long.

The 150 amp example is also incorrect. Because of Peukert 150 amp draw would likely last less than 2 hours to 50% SOC. When you pull that high a percentage of capacity the bank size effectively decreases to a fraction of its 20 hour capacity.