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  1. #1
    Join Date
    Oct 2017
    Location
    Sweden
    Posts
    41

    Default Litium batteries instead of a generator - will I be able to run my AC?

    Hi!

    After my 13.5kw generator have broken down I'm looking into if I really should replace it. I'm located in Sweden and I rarely use the AC which is the main reason for running the generator. The sound of the generator is a big drawback and I really don't like to run it all however for any purpose.

    For the same money as the generator I can get approx 1200ah usable hours of litium batteries and two Victron Multiplus 5kw inverter/chargers.
    My AC (60.000btu) needs 40amp when running in full mode after startup which would give me 30 hours of running capacity If I have understood the math right.

    Is it this easy? I've read so many posts saying you can't run the AC on batteries, so what I'm I missing?

    BR Krister
    Last edited by Brunan; 14-08-19 at 07:17.

  2. #2
    Join Date
    Mar 2002
    Location
    Greenwich
    Posts
    7,471

    Default Re: Litium batteries instead of a generator - will I be able to run my AC?

    How and when are you thinking of recharging them?

  3. #3
    Join Date
    Oct 2017
    Location
    Sweden
    Posts
    41

    Default Re: Litium batteries instead of a generator - will I be able to run my AC?

    Quote Originally Posted by RupertW View Post
    How and when are you thinking of recharging them?
    With shore power primarily and from running the main engines.

  4. #4
    Join Date
    Apr 2011
    Location
    Boat- Western Med
    Posts
    5,204

    Default Re: Litium batteries instead of a generator - will I be able to run my AC?

    http://www.frigomar.com/catalogo-fri...nditioning.pdf

    Theses do the lowest current draw , 16 A for max capacity on a 62,000 btu + low start ups .
    We have the 42,000 they are virtually silent too as are the air handlers.

    So our tiny (90 kg weight ) geny runs our Aircon .

    Thinking of residual values if you bin the geny .Think of the future owners needs self sufficiency, independence of far away anchorages etc etc .

    You could work on better sound proofing and if it’s the exhaust noise work on that too to improve the geny run experience.


    Sorry can’t answer your Q directly but I suspect the Li ion batts will deteriorate quickly on a boat not used and end up short charged quicker than say a tablet or phone which is always near a charge point .
    Then there’s over charging = heat issues = fire risk = insurance hassle ?


    I once had slightly hesitation with the starting bats on the main engines .
    Went off and anchored all day both fridges on full blast outside temp 36 degrees .
    Came to fire up the main engines and dead mans click .
    No problem I thought I have a x over switch ( to connect the house to the starters) ........ just turned over and quickly back to click .Oops !!

    No prob
    Ran the geny ( got ) its own bat ) , put the charger on .Waited 40 mins , I can see the bulk 60/80 ah go in from the saloon console.Turned the geny off .
    Then there was enough power to fully start the main engines as per normal .

    Thing is the main bats where not holding there charge for longer enough so 8 hrs at anchor after disconnect from shore power they where whacked .
    And the house whacked unfortunately too .

    Point is the geny + the charger was / is my get out of jail card ,re engine starting and slowly decaying bats .

  5. #5
    Join Date
    Feb 2010
    Location
    Mallorca(boat), Hampshire(home)
    Posts
    232

    Default Re: Litium batteries instead of a generator - will I be able to run my AC?

    Broadly speaking I agree with Porto's point re a penny being an important get out of jail card in certain circumstances.

    But to answer your question directly, I was in the (quite large and smart) Mastervolt showroom in Gouvia last week discussing lithium batteries. They told me of a recent installation they'd done in, I think, a c40 foot sailing boat - 10 (yes 10!) lithium batteries, comprehensive solar recharging capability and apparently it is specced to run the Aircon all night. To my mind the issue one can't ever get away from is that the huge amount of energy that the Aircon uses over, say, 10 hours, needs to be put back into the batteries somehow. So how?! Either massive recharging when back on shorepower, or acres of solar panels (not possible on a boat) or.... a genny!

    So I guess it's important to think about how the boat is used - occasional AC use for a few hours could work fine I guess. That seems like your pattern. In the Med I tend to run the AC most nights and just can't see lithium working - or at least can't see how I'd ever get the batteries fully recharged ready for the next night!

  6. #6
    Join Date
    Nov 2002
    Location
    Australia
    Posts
    5,895

    Default Re: Litium batteries instead of a generator - will I be able to run my AC?

    Quote Originally Posted by Brunan View Post
    For the same money as the generator I can get approx 1200ah usable hours of litium batteries and two Victron Multiplus 5kw inverter/chargers.
    My AC (60.000btu) needs 40amp when running in full mode after startup which would give me 30 hours of running capacity If I have understood the math right.

    Is it this easy? I've read so many posts saying you can't run the AC on batteries, so what I'm I missing?
    You're missing the fact that your lithium batteries are 1200ah at (presumably) 12v, and your AC is 40amps at 240v. Thus the AC is 9.6kw and you'd need 800amps at 12v to service that. You'll get about an 90mins if you're lucky and you'd be spanking the lithium batteries very very hard to provide that.

    That's why you can't run your air conditioning from batteries.

  7. #7
    Join Date
    May 2015
    Posts
    330

    Default Re: Litium batteries instead of a generator - will I be able to run my AC?

    Quote Originally Posted by rickp View Post
    You're missing the fact that your lithium batteries are 1200ah at (presumably) 12v, and your AC is 40amps at 240v. Thus the AC is 9.6kw and you'd need 800amps at 12v to service that. You'll get about an 90mins if you're lucky and you'd be spanking the lithium batteries very very hard to provide that.

    That's why you can't run your air conditioning from batteries.
    The above is correct you would be pulling around 800 amp out of the batteries if the aircon needed 40 amp at 240v

  8. #8
    Join Date
    Oct 2017
    Location
    Sweden
    Posts
    41

    Default Re: Litium batteries instead of a generator - will I be able to run my AC?

    Quote Originally Posted by Croftie View Post
    The above is correct you would be pulling around 800 amp out of the batteries if the aircon needed 40 amp at 240v
    Geez that's why I guess it's not possible. I will move on to the next step then investing how to use the AC only for heat (yes that we do in Sweden a lot) with a water heater and inverter combined.

  9. #9
    Join Date
    May 2015
    Posts
    330

    Default Re: Litium batteries instead of a generator - will I be able to run my AC?

    Quote Originally Posted by Brunan View Post
    Geez that's why I guess it's not possible. I will move on to the next step then investing how to use the AC only for heat (yes that we do in Sweden a lot) with a water heater and inverter combined.
    Just remember if it needs xxamp @ 240v then it needs app 20 times xxamp at 12v. This is one of the reasons bigger boats use 24v systems rather than 12v as it halves the amperage and therefore smaller cables can be used.

  10. #10
    Join Date
    Mar 2002
    Location
    Greenwich
    Posts
    7,471

    Default Re: Litium batteries instead of a generator - will I be able to run my AC?

    Quote Originally Posted by Croftie View Post
    The above is correct you would be pulling around 800 amp out of the batteries if the aircon needed 40 amp at 240v
    So on shorepower you use 3 phase only for AC? Is the 40amps at 240v correct?

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