Actual Ah demand for AirCon

[sailingharry]

Originally Posted by s/v Jedi

We really need to know what you have now and intend to keep using: what shore power, solar, which solar controllers, which alternator with which regulator, which AC charger, inverter or inverter/charger etc.

Note: you don’t have to change the windlass, powered winch etc. when you change the house battery to 24V or even 48V.

Also, I believe you wrote you don’t have a generator. Do you intend to buy a portable generator? How do you plan to generate the daily energy that is needed?

Current batteries: 740Ah of quality AGM (northstar).
Current generation: 500W of shattered panels being replaced by 2x400W bifacial on the arch (Victron MPPT, but still deciding between your recommendation for series vs individual controllers) not yet installed. 2x100W Solbian flexible garbage on the bimini, maybe good for 100W total currently on Genasun MPPT but upgrading to the Victron MPPT from the shattered arch panels. 130A and 140A Powerline alts on the engine each with dedicated Balmar regulators, good for 250+ cold, 150 after an hour of run time (they will run full output -- temperature limited -- for over an hour to get to Acceptance). 40A Watt and Sea, although last summer it stopped working and I haven't figured out why. In addition to the Multiplus, I have a nifty Victron Centaur 50A multi-input (120/240V) battery charger on a dedicated shore power connection installed for an overseas trip (2012, before my time) that I can (rarely) feed from a separate shore connection for faster charge rates.
Current consumption: About 250Ah/day, best guess. I have a Link2000, but of course it can't differentiate between "load" and "charge." Primary loads are a fridge and freezer (some careful load tests indicate maybe 100Ah/day), and morning toast/coffee on 110V appliances (easily 50Ah/day). I have a Spectra 6GPH water maker that I have tested (and re-pickled) but have never needed as water in the NE is plentiful -- I realize in Caribbean cruising that may be a new demand.
Daily power balance: I am upping my solar significantly. In 2022 (right after putting 500W on my arch!) I had a nasty accident in Montreal and destroyed most of my arch solar. Still, we "mostly" met our daily demand by charging during transit, with minimal amounts of "run engine to charge." Our consumption profile won't change, but our generation should change (much more solar, and ideally more effective charge parameters on the LFP -- but since AGM can take all I can give it until around 90-95% SOC, not a lot of improvement available).
Air Conditioning is very much a "future consideration." I don't have it, and don't often wish for it (and don't want to give up the locker it would go in!). But if I can include it into the battery design, I don't have to redesign. The feedback here indicates that 300Ah is a reasonable overnight buffer, especially if I run the engine for 30 minutes in the evening (both supporting initial cool down and charging batteries). I fully understand that I'll need the engine the next day to replenish that 300Ah, either in transit or charging at anchor. A suitcase generator might be an option too, but my opinion of that is rather negative (but running it from Noon to 2PM might fit with my general negative view)
Yes, a 24V battery can very nicely support existing high power (but low energy) devices like an inverter or windlass, by use of a 150Ah 12V bank with DC-DC. But the ROI drops. And I'd still need a brand new inverter to replace my 2 year old inverter, and a pair of alternators to replace my alternators (hmm.... is it possible to pump 3kW uphill through a DC-DC system -- or even pull out the 3 phase AC and push it through transformers? -- not likely, but I'm not saying "no.") In my case, I'd need an inverter, 2 alternators, a 12V bank, 2 Victron MPPT controllers, assorted DC/DC, all to have the inverter use smaller cables. If I hadn't been forced (break/fix, not planned upgrade) to replace my inverter 2 years ago, it would be a slightly different story.

[s/v Jedi]

Originally Posted by sailingharry

Current batteries: 740Ah of quality AGM (northstar).
Current generation: 500W of shattered panels being replaced by 2x400W bifacial on the arch (Victron MPPT, but still deciding between your recommendation for series vs individual controllers) not yet installed. 2x100W Solbian flexible garbage on the bimini, maybe good for 100W total currently on Genasun MPPT but upgrading to the Victron MPPT from the shattered arch panels. 130A and 140A Powerline alts on the engine each with dedicated Balmar regulators, good for 250+ cold, 150 after an hour of run time (they will run full output -- temperature limited -- for over an hour to get to Acceptance). 40A Watt and Sea, although last summer it stopped working and I haven't figured out why. In addition to the Multiplus, I have a nifty Victron Centaur 50A multi-input (120/240V) battery charger on a dedicated shore power connection installed for an overseas trip (2012, before my time) that I can (rarely) feed from a separate shore connection for faster charge rates.
Current consumption: About 250Ah/day, best guess. I have a Link2000, but of course it can't differentiate between "load" and "charge." Primary loads are a fridge and freezer (some careful load tests indicate maybe 100Ah/day), and morning toast/coffee on 110V appliances (easily 50Ah/day). I have a Spectra 6GPH water maker that I have tested (and re-pickled) but have never needed as water in the NE is plentiful -- I realize in Caribbean cruising that may be a new demand.
Daily power balance: I am upping my solar significantly. In 2022 (right after putting 500W on my arch!) I had a nasty accident in Montreal and destroyed most of my arch solar. Still, we "mostly" met our daily demand by charging during transit, with minimal amounts of "run engine to charge." Our consumption profile won't change, but our generation should change (much more solar, and ideally more effective charge parameters on the LFP -- but since AGM can take all I can give it until around 90-95% SOC, not a lot of improvement available).
Air Conditioning is very much a "future consideration." I don't have it, and don't often wish for it (and don't want to give up the locker it would go in!). But if I can include it into the battery design, I don't have to redesign. The feedback here indicates that 300Ah is a reasonable overnight buffer, especially if I run the engine for 30 minutes in the evening (both supporting initial cool down and charging batteries). I fully understand that I'll need the engine the next day to replenish that 300Ah, either in transit or charging at anchor. A suitcase generator might be an option too, but my opinion of that is rather negative (but running it from Noon to 2PM might fit with my general negative view)
Yes, a 24V battery can very nicely support existing high power (but low energy) devices like an inverter or windlass, by use of a 150Ah 12V bank with DC-DC. But the ROI drops. And I'd still need a brand new inverter to replace my 2 year old inverter, and a pair of alternators to replace my alternators (hmm.... is it possible to pump 3kW uphill through a DC-DC system -- or even pull out the 3 phase AC and push it through transformers? -- not likely, but I'm not saying "no.") In my case, I'd need an inverter, 2 alternators, a 12V bank, 2 Victron MPPT controllers, assorted DC/DC, all to have the inverter use smaller cables. If I hadn't been forced (break/fix, not planned upgrade) to replace my inverter 2 years ago, it would be a slightly different story.

You wouldn’t need to buy new MPPT controllers because they work on higher battery voltages but yes, the Multiplus and alternators need replacement for higher voltage. In your case, I have doubts if it is worth the cost.

Do you use propane gas?

To run A/C from solar you need much more solar than what you can install. I would say a minimum of 1,500W and that is for an efficient variable rpm unit.

We have 2,550W and can run an old power hungry A/C for a couple hours daily on solar.

[CaptainRivet]

Originally Posted by s/v Jedi

You wouldn’t need to buy new MPPT controllers because they work on higher battery voltages but yes, the Multiplus and alternators need replacement for higher voltage. In your case, I have doubts if it is worth the cost.

Do you use propane gas?

To run A/C from solar you need much more solar than what you can install. I would say a minimum of 1,500W and that is for an efficient variable rpm unit.

We have 2,550W and can run an old power hungry A/C for a couple hours daily on solar.

Agree 1500W minimum for AC in 12V DC...Marbu.

12V is ok, suggest 1200AH with 4x 1p4S with each a JK BMS 200A 2A active balancer plus class T or NH 125A fuse and BMV712 shunt to battery busbar.

From description more likely 300AH dailiy use, 300AH for AC and 600AH as buffer when you harvest what you can...you have and will have to less solar but big alternators so anytime you motor you will get that bank full or at least nearly but on anchor will gradually drain it down to 30%SOC in 8-10days as you don't have enough solar to cover your daily needs.

Suggest to put fixed bifacial on your bimini too.
800W bifacial will give you 3kw/day...not enough but you have big alternators.

[sailingharry]

Originally Posted by s/v Jedi

Do you use propane gas?

To run A/C from solar you need much more solar than what you can install. I would say a minimum of 1,500W and that is for an efficient variable rpm unit.

We have 2,550W and can run an old power hungry A/C for a couple hours daily on solar.

Yes, we have propane. Twin 10lb. We cook (a lot) and find that after 4 months aboard we still have 1/2 of the second tank, so figure we can get close to 6 months on that.



I should re-emphasize that A/C would never be a "daily" thing, and I don't expect solar to replace that power. It would be a rarity, and running the engine (either at anchor or on transit) the next day would be almost guaranteed.

[sailingharry]

Originally Posted by CaptainRivet

Suggest to put fixed bifacial on your bimini too.
800W bifacial will give you 3kw/day...not enough but you have big alternators.

Bimini is a non-starter. First, non-negotiable, is the asethetic review board had denied my request. I need to keep her happy. But I also have split backstays over the bimini, so the odds of shadow lines are high and my understanding is that is quite unhelpful.

[CaptainRivet]

Originally Posted by sailingharry

Bimini is a non-starter. First, non-negotiable, is the asethetic review board had denied my request. I need to keep her happy. But I also have split backstays over the bimini, so the odds of shadow lines are high and my understanding is that is quite unhelpful.

Happy wife happy life.
But well then ypu are very limited. Good you cook with propane.
You can start with 600AH then add another 304AH battery but i would spec for 1200AH. Its simply you have the battery busbar so you can add 2 more. If you don't draw more current but only add for more capacity you don't need bigger battery cable or fuses or...all stays the same. You just add 2 batteries with their BMS and fuse and Shunt.

Yes you don 't generate additional energy when having 1200AH but you always harvest when engine on which then lasts you another 6 till 10days as solar replaces some but not all and you live off that buffer. And lifepo4 doesn’t have or need to be charged full...my bank stays mostly between 50 and 85% SoC, in side season its maybe 100%SOC once or twice a month.

[s/v Jedi]

Originally Posted by sailingharry

Yes, we have propane. Twin 10lb. We cook (a lot) and find that after 4 months aboard we still have 1/2 of the second tank, so figure we can get close to 6 months on that.

I should re-emphasize that A/C would never be a "daily" thing, and I don't expect solar to replace that power. It would be a rarity, and running the engine (either at anchor or on transit) the next day would be almost guaranteed.

So here is the problem with your plans… you cook with propane so the only high power appliance would be the A/C which you would run only now and then. The point is that you need to install very powerful inverter(s) to run that and that’s the only reason you need that capacity.

So for sure you would need to buy a variable rpm A/C unit which has a very soft start, in which case you would be okay with a single Victron Multiplus 3000.

[CaptainRivet]

Originally Posted by s/v Jedi

So here is the problem with your plans… you cook with propane so the only high power appliance would be the A/C which you would run only now and then. The point is that you need to install very powerful inverter(s) to run that and that’s the only reason you need that capacity.

So for sure you would need to buy a variable rpm A/C unit which has a very soft start, in which case you would be okay with a single Victron Multiplus 3000.

why AC Aircons...12V Marbu and job done and 10k less in the bank. With that minimum energy you need DC aircon watercooled for max efficency...every mA counts.

[sailingharry]

Originally Posted by CaptainRivet

why AC Aircons...12V Marbu and job done and 10k less in the bank. With that minimum energy you need DC aircon watercooled for max efficency...every mA counts.

I know the marketing for the DC units, but I'm highly skeptical of real world benefits. Effiency in A/C units has been the Holy Grail of land based systems for decades, and no one has been installing big DC rectifier systems to get huge improvements in efficiency. And, some DC refrigeration systems (the ubiquitous Danfoss, for instance), take the incoming DC and turn it into 3-phase AC to run the compressors.


My general suspicion is that running a DC wire (at 12V, no less) 20 feet out and back to an A/C unit would take minimum 6ga, maybe #4, to run an A/C, with associated losses from ~50A. If DC systems were magically significantly more efficient, AC systems would start off with a big AC-DC converter, and then suddenly be just as efficient without the big wires and I^2R losses.


This PS article, https://www.practical-sailor.com/sys...ning-at-anchor, says this:
Intuitively, air conditioning powered by 12-volt DC system should be more efficient than one plugged into 120-volt AC. In fact, the difference in efficiency between 12 volts and 120 volts is quite small.


I've not been able to find any compelling tear-and-compare articles. Most of what I see is either manufacturer propaganda videos, or users that compare the listed specs -- none that compare Ah consumed between two similar sized units for similar conditions with similar maintained temperatures. But when the DC makers claim "game changing" efficiency improvements, my Spidey Sense starts tingling.

[thinwater]

Originally Posted by sailingharry

Bimini is a non-starter. First, non-negotiable, is the asethetic review board had denied my request. I need to keep her happy. But I also have split backstays over the bimini, so the odds of shadow lines are high and my understanding is that is quite unhelpful.

I too have a review board.


This question came up, I explained the AC away from the dock depended on generous solar, and she came around. Sometimes there is cold hard math, sort of like gravity.



Happy wife when the AC worked!

[CaptainRivet]

Originally Posted by sailingharry

I know the marketing for the DC units, but I'm highly skeptical of real world benefits. Effiency in A/C units has been the Holy Grail of land based systems for decades, and no one has been installing big DC rectifier systems to get huge improvements in efficiency. And, some DC refrigeration systems (the ubiquitous Danfoss, for instance), take the incoming DC and turn it into 3-phase AC to run the compressors.


My general suspicion is that running a DC wire (at 12V, no less) 20 feet out and back to an A/C unit would take minimum 6ga, maybe #4, to run an A/C, with associated losses from ~50A. If DC systems were magically significantly more efficient, AC systems would start off with a big AC-DC converter, and then suddenly be just as efficient without the big wires and I^2R losses.


This PS article, https://www.practical-sailor.com/sys...ning-at-anchor, says this:
Intuitively, air conditioning powered by 12-volt DC system should be more efficient than one plugged into 120-volt AC. In fact, the difference in efficiency between 12 volts and 120 volts is quite small.


I've not been able to find any compelling tear-and-compare articles. Most of what I see is either manufacturer propaganda videos, or users that compare the listed specs -- none that compare Ah consumed between two similar sized units for similar conditions with similar maintained temperatures. But when the DC makers claim "game changing" efficiency improvements, my Spidey Sense starts tingling.

As difference is very small installing DC is simpler and you are not depending on inverter.
Most that i know thrown out the AC AC and went for DC when liveaboard. Marbu or the Chinese factory where the Marbu base units come from.
Dc are watercooled; AC not.

[shimari]

We've multiple Frigomar Self-contained BLDC inverter units. Ours run on AC, but they've announced 24v and 48v systems now.

Our real world measurements match-up well with their posted performance curve at https://www.frigomar.com/en/products...inverter-bldc/



Initially, the 16K BTU until draws about 1kw....eventually it goes down to a few hundred KW. If we turn ECO mode on, it goes even lower.

The units are expensive, unfortunately.

[CaptainRivet]

https://www.alibaba.com/product-deta...251613071.html

These are the AC that marbu use ase base unit and then fine-tuned.
That last 5% always cost exponential. Would just use them and spend the saved money somewhere else. Ordered one too for my owner cabin.

[SV Confianza]

Originally Posted by sailingharry

I know the marketing for the DC units, but I'm highly skeptical of real world benefits. Effiency in A/C units has been the Holy Grail of land based systems for decades, and no one has been installing big DC rectifier systems to get huge improvements in efficiency. And, some DC refrigeration systems (the ubiquitous Danfoss, for instance), take the incoming DC and turn it into 3-phase AC to run the compressors.


My general suspicion is that running a DC wire (at 12V, no less) 20 feet out and back to an A/C unit would take minimum 6ga, maybe #4, to run an A/C, with associated losses from ~50A. If DC systems were magically significantly more efficient, AC systems would start off with a big AC-DC converter, and then suddenly be just as efficient without the big wires and I^2R losses.


This PS article, https://www.practical-sailor.com/sys...ning-at-anchor, says this:
Intuitively, air conditioning powered by 12-volt DC system should be more efficient than one plugged into 120-volt AC. In fact, the difference in efficiency between 12 volts and 120 volts is quite small.


I've not been able to find any compelling tear-and-compare articles. Most of what I see is either manufacturer propaganda videos, or users that compare the listed specs -- none that compare Ah consumed between two similar sized units for similar conditions with similar maintained temperatures. But when the DC makers claim "game changing" efficiency improvements, my Spidey Sense starts tingling.

I wrote up our research and comparisons here and what we’re experiencing in the real world: https://www.clevermariner.com/post/c...-from-the-dock

There is definitely still a debate about whether variable speed ACs are worth the extra cost. Mabru for instance maxes out at 12k btu which is too small for many salons. And from their stats it seems like their system is definitely optimized for the 12k btu size, since the smaller ones are less efficient per btu. I also have yet to find much in the way of real world data on them other than marketing pamphlets that show how much you really can save running the compressor more slowly.

Also, when we do decide to run our A/C at anchor, it’s mostly pegged at 100% anyway.

[ekelly36]

Question.... as I am also planning to add AC because well.... the wife wants it.... for this really I was just thinking about either installing a overhead RV AC aircon or attempting to place a AC minisplit system, both will come with challenges but from all the reading I have done I have a couple options..... 4k inverter with 1200Ah lifepo4 and a small gen to make up the difference for the 1200w solar or smaller everything else and a little bigger generator, seeming as I will need to carry gas in cans for the dinghy either way is ok with me.... of course I could be missing something but the RV units and minisplits advertise 10-20Ah usage if memory serves..... on a 1200 Ah bank 20 amps an hour for the AC is not a deal breaker for me.... I admit actual use and just research are completely different things so I guess we will see...... The MAIN issue is.... the wife lol.... she has to be comfortable or well.... it wont be fun lol