A/C and electrical Upgrade

[LivingWhale]

We're about to take possession (10 days and counting) of a 2017 Nautitech Open 40. It isn't equipped with A/C or a generator. It has a single 250W solar panel. Ideally, we would like to add battery powered A/C, enough lithium to support the A/C and the rest of the boat (keeping in mind the battery bank is below our berth so we don't want to generate too much heat recharging), and additional solar on the roof which will hold 4 large panels. I wish I were knowledgable enough to do it myself, but sadly I'm not. We're in HIlton Head SC and would like to take the boat somewhere to have this done, but hopefully not too far away. Any suggestions?

[NPCampbell]

The only snippet of advice I can offer is to zone appropriately so you can only condition the rooms that you need to. I'd use DC A/Cs to be able to run the A/C without having to upsize or involve the main inverter. I think the trade-off is having to run really large gauge wire to handle the higher current.

The efficiency of the units does vary widely. I've seen both 4k BTU units and 10k BTU (variable speed) units both draw 400 watts per hour.

[LivingWhale]

Originally Posted by NPCampbell

The only snippet of advice I can offer is to zone appropriately so you can only condition the rooms that you need to. I'd use DC A/Cs to be able to run the A/C without having to upsize or involve the main inverter. I think the trade-off is having to run really large gauge wire to handle the higher current.

The efficiency of the units does vary widely. I've seen both 4k BTU units and 10k BTU (variable speed) units both draw 400 watts per hour.

Thank you! I could always get a generator and go that way, but it would be nice if this method works and works well.

[flee27]

If you look at some of the variable speed units you can do a good bit better than 400 watts in the low settings. As NPCampbell said, what matters most is only trying to AC the area absolutely needed. In most cases this is your sleeping area. If you are in a large cabin it might even mean putting a curtain up at the end of your bed. It is not practical to think you going to AC the whole boat without a generator.

Also keep in mind that you have to replenish the power you remove from your batteries. Some people seem to focus too hard on battery bank size without consideration to how you are going to recharge them. Your electrical system has to work as a system.

Good luck with your new boat

Foster

[LivingWhale]

Originally Posted by flee27

If you look at some of the variable speed units you can do a good bit better than 400 watts in the low settings. As NPCampbell said, what matters most is only trying to AC the area absolutely needed. In most cases this is your sleeping area. If you are in a large cabin it might even mean putting a curtain up at the end of your bed. It is not practical to think you going to AC the whole boat without a generator.

Also keep in mind that you have to replenish the power you remove from your batteries. Some people seem to focus too hard on battery bank size without consideration to how you are going to recharge them. Your electrical system has to work as a system.

Good luck with your new boat

Foster

Agreed and I know that running lithium down and then brining it back up produces heat from the batteries and they are located under my berth . So it will be a delicate balance for sure. I asked a mechanic and he suggested I go with a generator in the traditional set-up. If thta makes the most sense, then that's what I'll do. It's really hard to know.

[ItDepends]

Your approach is a bit backwards. You FIRST need to figure out how much energy you will use, then how you are going to MAKE the energy, and LAST you figure out how you need to store it (that's the battery part).

You will also have a bit of a spiral here... adding black solar panels to the deck will increase the heat transferred into the cabin, with means you need a bigger AC unit, which means more solar... It's one of the reasons that some catamarans need AC units bigger than a 5000 sq foot house.

I would suggest before you make final decisions about what to do, you read carefully the AC blog on coastalclimatecontrol.com Lots of good information from a very knowledgable and experienced source.

[LivingWhale]

Originally Posted by ItDepends

Your approach is a bit backwards. You FIRST need to figure out how much energy you will use, then how you are going to MAKE the energy, and LAST you figure out how you need to store it (that's the battery part).

You will also have a bit of a spiral here... adding black solar panels to the deck will increase the heat transferred into the cabin, with means you need a bigger AC unit, which means more solar... It's one of the reasons that some catamarans need AC units bigger than a 5000 sq foot house.

I would suggest before you make final decisions about what to do, you read carefully the AC blog on coastalclimatecontrol.com Lots of good information from a very knowledgable and experienced source.

Perfect - thanks! I'm always looking for more things I can research and learn on.

[Peeew]

I did talk to an electrical company doing a big project on a new boat to be able to run 3 a/c zones from a central compressor/condenser setup. This included a big bank (48v I remember) of lithiums to run the air conditioning, more lithium batteries for the house bank. A big arch fabricated to carry a lot of solar panels. Engine alterations to manage two big alternators. Lots of wiring. Etc etc. The work seemed to be well thought out and professionally installed. Cost? $160,000.00 US. This allowed them to run the air conditioning for 10 hours in most conditions.
A diesel generator would seem to be a better choice in my mind.

[shimari]

Good advice from everyone so far. Definitely compute your power requirements to size the battery bank properly.

There are a number of threads on A/C which I recommend. Having just installed new A/C, I can share my choice. I opted for the Frigomar inverter units. It does place the inverter on the critical path, but if I lose my Combi I've larger issues than not having A/C.

I've not done a controlled power measurement yet, but the initial numbers look similar to specs from Frigomar. Our 16k BTU unit pulls about 1KW when running 100%.

[Madehn]

everything i have looked at so far says that AC with lithium batteries is really not ready for prime time yet- you will spend a crap load of money going down that rabbit hole. If you want to do it just to do it, i think you will end up with a system that is marginally useful, complicated and expensive. JMHO but i would go with a generator - 5 years from now my answer might be different but i think that is the state of the technology presently. Best of luck

[LivingWhale]

Originally Posted by Madehn

everything i have looked at so far says that AC with lithium batteries is really not ready for prime time yet- you will spend a crap load of money going down that rabbit hole. If you want to do it just to do it, i think you will end up with a system that is marginally useful, complicated and expensive. JMHO but i would go with a generator - 5 years from now my answer might be different but i think that is the state of the technology presently. Best of luck

I think you may be correct.

[LivingWhale]

Originally Posted by Peeew

I did talk to an electrical company doing a big project on a new boat to be able to run 3 a/c zones from a central compressor/condenser setup. This included a big bank (48v I remember) of lithiums to run the air conditioning, more lithium batteries for the house bank. A big arch fabricated to carry a lot of solar panels. Engine alterations to manage two big alternators. Lots of wiring. Etc etc. The work seemed to be well thought out and professionally installed. Cost? $160,000.00 US. This allowed them to run the air conditioning for 10 hours in most conditions.
A diesel generator would seem to be a better choice in my mind.

and 160K would definitely be a no go. Hate paying for the generator and adding the weight. Not to mention the cost of diesel. But alas it's similar to electric cars which everyone thinks is the answer, but batteries have to be replaced every 10 years and at a cost more than gasoline. Not to mention the environmental impact is similar when you take into account how the energy is generated and all the other challenges. Great hype but not as logical as it first seems.

[LivingWhale]

Originally Posted by shimari

Good advice from everyone so far. Definitely compute your power requirements to size the battery bank properly.

There are a number of threads on A/C which I recommend. Having just installed new A/C, I can share my choice. I opted for the Frigomar inverter units. It does place the inverter on the critical path, but if I lose my Combi I've larger issues than not having A/C.

I've not done a controlled power measurement yet, but the initial numbers look similar to specs from Frigomar. Our 16k BTU unit pulls about 1KW when running 100%.

Thanks! I'll research for sure

[FlyingScot]

Best place for solar on most catamarans is off the back of the bimini where they get the least amount of shade. You'll need the following:
2000wp of high quality solar (better yet 2500wp+)
Efficient A/C unit and limited cooling space (think variable speed and just your sleeping cabin)
Large battery bank that can recharged efficiently (think LiFePO4 and minimum 1000Wh, 1500Wh is better)
Another charging method or two, besides a little Honda or your stock alternators. Battery banks this big need a lot of power to recharge them, above and beyond your normal usage.

We haven't implemented our system yet, but will soon. We choose:
LG 435wp bifacial panels x 5 hanging off the back of the hard bimini on our 40' cat. We make an average of 6kwh per day now with 1440wp, but hope to make 10kwh when we upgrade.
Mabru 12v 12K btu/hr x 2 air conditioners.
330AH Victron LiFePO4 (@12v) x 4 House Batteries
Balmar XT 170A with Wakespeed Controllers x 2 and Victron Lynx BMS/Cerbo GX.

From my research it should integrate well and be a little easier to install.

My intention is to be able to cool our cabin overnight when required. We are happy with 27-28c for sleeping. If you like it colder, you will likely need more.

Good luck with your research. Be prepared to spend serious money.
You can do for less with traditional generator, but not being factory installed, I'd guess 20K for that option, not including A/C.

[SV Confianza]

Originally Posted by LivingWhale

I think you may be correct.

Going Lithium has a ton of benefits. We made the conversion 2 years ago. But I wouldn't do it just for air conditioning.

We converted because we wanted to live and work on the boat and have a more household like power experience (running hair dryers etc), longer life span, and faster charging.

We are about to upgrade our ACs and looking at Marinaire.