Is running 1600BTU MarinAire on battery/solar possible?

[valhalla360]

Originally Posted by KingGuppy

Does anyone run a similar AC unit off of solar/battery, using a soft/easy start device?

MarinAire 16k BTU:
Max. input consumption: 1480 W
Running Current: 10.8 A
Strating Current: 17.6 A

We have around 1000w of Solar, and 1200ah of batteries.

Our invertor is a Magnum 3000:
Output Power 3,000W
Peak Watts 3,500W
Output Voltage 120 VAC
Output Current 25.0 amps

Our goal is to be able to run the AC a few hours during the day when the sun is out, and then an hour or two at night.

We plan to add another 300w solar, and change batteries to lithium, but we weren't sure if we need to upgrade the inverter as well. Or if this would be possible with that setup.

Thanks for the help.

Possible...yes.
Practical...no

If the running current is 10.8amps at 120v, you are drawing just shy of 1.3KW, which means you need 1.3KWH for every hour of expected run time. Let's say 3hrs in the afternoon and 2hrs in the evening. That means you will be using about 6.5KWH just for the air/con. Assuming the system isn't 100% efficient and you have some other electrical loads, that's probably somewhere on the order of 8KWH per day consumed.
- Your 1000w of panels will likely generate somewhere on the order of 4KWH per day (4 times the nominal rating is a good estimate), so unless you are running a generator, you will need to double your solar array size if you want to use it regularly.
- 1200ah of battery at 12v is 14.4KWH but with lead acid, you can't use 100% (assuming they are relatively new and in good condition). At best, you are looking at 50% (from 100% to 50% charge), so 7.2KWH of usable power if full. In practice, it may be difficult to reach 100%. The last 10-20% takes a very long time to refill as the batteries accept much lower amperage. So you may only get 40% of the rating in practice. If the bank is older and doesn't hold the rated power, it could be even less.

With a soft start, the inverter may work to kick the compressor over. If it does, it should be able to work as long as you don't exceed the maximum continuous rating for the inverter (they may or may not provide that info with the unit). Also, make sure the cabling to the battery bank is as short as possible and thick enough to keep voltage drop minimized. Undersized, long or corroded cables can waste a lot of power.

2-3hr per day is probably doable but unless your boat is far better than average in terms of insulation, don't expect great things. Most boats are horribly insulated and will quickly heat up as soon as the air/con is turned off.

[KingGuppy]

Originally Posted by valhalla360

Possible...yes.
Practical...no

If the running current is 10.8amps at 120v, you are drawing just shy of 1.3KW, which means you need 1.3KWH for every hour of expected run time. Let's say 3hrs in the afternoon and 2hrs in the evening. That means you will be using about 6.5KWH just for the air/con. Assuming the system isn't 100% efficient and you have some other electrical loads, that's probably somewhere on the order of 8KWH per day consumed.
- Your 1000w of panels will likely generate somewhere on the order of 4KWH per day (4 times the nominal rating is a good estimate), so unless you are running a generator, you will need to double your solar array size if you want to use it regularly.
- 1200ah of battery at 12v is 14.4KWH but with lead acid, you can't use 100% (assuming they are relatively new and in good condition). At best, you are looking at 50% (from 100% to 50% charge), so 7.2KWH of usable power if full. In practice, it may be difficult to reach 100%. The last 10-20% takes a very long time to refill as the batteries accept much lower amperage. So you may only get 40% of the rating in practice. If the bank is older and doesn't hold the rated power, it could be even less.

With a soft start, the inverter may work to kick the compressor over. If it does, it should be able to work as long as you don't exceed the maximum continuous rating for the inverter (they may or may not provide that info with the unit). Also, make sure the cabling to the battery bank is as short as possible and thick enough to keep voltage drop minimized. Undersized, long or corroded cables can waste a lot of power.

2-3hr per day is probably doable but unless your boat is far better than average in terms of insulation, don't expect great things. Most boats are horribly insulated and will quickly heat up as soon as the air/con is turned off.

Appreciate the breakdown of it in this. We definitely will need a bit more solar and a bit less AC.

[wingssail]

Originally Posted by KingGuppy

Yeah, that would be a lot of engine running.

We had planned to add more solar, to eventually get to around 1400watts. With the AC mostly being run when the sun is out and its hottest, it may not be a complete drain.

Definitely don't want to rely on engines daily for it. What do you think I would need solar wise to make it possible?

I think you need to get that answer from one of the experts on this forum and that isn't me.

But just a simplified calculation would be: Assuming you need 1000-1200 watts to keep that unit running (roughly 100amp from a 12v system) and you use it 4-6 hours a day max, you'll use up to 600 amp hours or 7200 watt hours daily. Consider that you there will be losses putting that amperage into your FLA batteries, plus losses converting it into 120VAC, I'd guess you need 10,000 watt hours daily, and that does not consider that solar panel ratings are optimistic. At six hours of good solar per day that is 1600 unshaded watts of solar panels (delivering at least a constant 135 amps INTO the batteries or your electrical bus) and a very well engineered and installed system to back it up. Look the actual output of your current 1000 watt array to see what percentage of the rated output you can actually count on to receive.

[KingGuppy]

Originally Posted by wingssail

I think you need to get that answer from one of the experts on this forum and that isn't me.

But just a simplified calculation would be: Assuming you need 1000-1200 watts to keep that unit running (roughly 100amp from a 12v system) and you use it 4-6 hours a day max, you'll use up to 600 amp hours or 7200 watt hours daily. Consider that you there will be losses putting that amperage into your FLA batteries, plus losses converting it into 120VAC, I'd guess you need 10,000 watt hours daily, and that does not consider that solar panel ratings are optimistic. At six hours of good solar per day that is 1600 unshaded watts of solar panels (delivering at least a constant 135 amps INTO the batteries or your electrical bus) and a very well engineered and installed system to back it up. Look the actual output of your current 1000 watt array to see what percentage of the rated output you can actually count on to receive.

Absolutely. I need to do a lot more research and then get some real-world numbers before making any changes. Thanks for mathing it out for us.

[jt11791]

I'm in the Caribbean now (and have been since early Nov.) My 1000W solar array can give 4KWh in a summer day, but in December I've been averaging more like 2.5KWh. Shorter days, lower sun angle, clouds.... At this time of year that doesn't even cover my non-AC house loads, refrig, lights, etc.

I have a big LiFePO house bank (1200Ah) but I don't even think about running my AC from it as that would mean I'd need to run the generator to recharge, so might as well just run the generator for the AC (which I don't need at anchor anyway). In my cruising experience, AC is for marinas and not needed otherwise.

[KingGuppy]

Originally Posted by jt11791

I'm in the Caribbean now (and have been since early Nov.) My 1000W solar array can give 4KWh in a summer day, but in December I've been averaging more like 2.5KWh. Shorter days, lower sun angle, clouds.... At this time of year that doesn't even cover my non-AC house loads, refrig, lights, etc.

I have a big LiFePO house bank (1200Ah) but I don't even think about running my AC from it as that would mean I'd need to run the generator to recharge, so might as well just run the generator for the AC (which I don't need at anchor anyway). In my cruising experience, AC is for marinas and not needed otherwise.

Thank you for the real-world numbers/examples.

Without AC, what are some average daily temps you're living with inside? And what about at night?

[jt11791]

Originally Posted by KingGuppy

Thank you for the real-world numbers/examples.

Without AC, what are some average daily temps you're living with inside? And what about at night?

Daytime highs in the USVI this week are 80-81F (27C), about 74F (23C) at night. Humidity is around 68% today. It's damn near perfect.

[170122]

Must see, not all air conditioning units are equal some consume a fraction than others and last much longer
https://youtu.be/nFA3FNAHv_I

[170122]

18000 consuming less than a 16000 BTU, then after cooling the vessel it will slow down to produce a about 12000 BTU and only 4.5 amps or 5 amps including the pump..

[jgrebe]

Maybe someone else has mentioned it but you need to factor in the fact that the useful (working) storage of lead acid batteries is about 60% of their nameplate rating. Take them lower than 40% charge frequently and you will damage the batteries

[merrydolphin]

Bottom line: Yes, it can be done…………….but it isn’t very practical. Will empty your batteries pretty quick. However, with a soft start, a honda 2000 will run one. The combo could be a winner.

[girouxkj]

Some cleaver HVAC engineer will design a way for a mini-split condenser unit to use seawater as its heat sink ala water to air heat pumps used both commercially and for residential HVAC systems.

[sailor1026]

Yes. We have 540Ah LFP battery bank and Victron 12v/3000W/150A inverter/charger. It will start and run our CruiseAir 16KBTU aircon in either heating and cooling mode (basically a heat pump). This includes the water pump">raw water pump, which is also 120v. Total is 10-11A at 120v. It pulls 120A from the batteries, so we can only run for a few hours, but that's enough for us. We don't have a soft-start.
We typically run it for an hour or so before bedtime in the hot/humid/windless Chesapeake summer. We turn it off before going to sleep. About 2am we open the boat since it typically cools off by then. In the cold spring/fall mornings we'll get up and start it, go back to bed for 30 minutes. It makes breakfast more enjoyable.

[Nibiruwayne]

Lots of good answers- I choose a genset . Also is a redundant way to recharge all banks when away from the dock and/ or on the hook.

[jackrabbit59]

I run two 16K units off my lithium 900 amp hour batteries, but not for long time periods. I have all electric kitchen as well, microwave, convection oven and induction coooktop. Twin 3000 watt inverters running 240 volts AC. That splits the air con units into half making it easier on the inverters. The Victron inverters handle the start up bump without the soft starts.
Things I have learned about running large AC draws on the inverters are
1. Make certain you have sufficient gauge wiring from the batteries to the inverters. You cannot go too big. I have individual voltage meters monitoring the lines at the batteries and at the inputs of the inverters. You will be amazed at the voltage drops as the wires heat up. You need a minimum of 4 0 wire as short as possible. Put in twin 4 0 wires if you can. Your inverter will love you for it.
2. If you have an on/off switch between the batteries and inverter (highly recommended) make certain it is rated high enough. I had the red BlueSea on/off switches and they failed. Melted internally and became intermit. They were rated at 300 to 350 amps. Upgrade them to the gray BlueSea switches that handle 600 amps. When the air con comes on it will go over the 300 amps no matter what the books say. Every extra inch of wire eats amps and increases wire temperature so keep them short.
I have 1200 watts of solar as well. Easy to run the one of the ac units during the day if the sun is shinning bright. But at night I run them for about 20 minutes to cool things off and then only intermitted. Need the generator if I want to run both overnight.
Just bought another 300 amp hour lithium to add on so I can run my AC longer at night in the master cabin. Also considering the new DC air con unit to avoid the inverters or a smaller ac btu unit for the master cabin, maybe 7 or 8K btu. Then I could run that unit overnight without generator.
Also you can add a second inverter as a stacked unit if your Magnum is less than 10 years old. But you would want to make sure it is compatible. Check with Magnum before going that way. If they units don't communicate correctly you can fry the batteries and the inverters in a heartbeat.
Good luck. I love running my ac without the generator.