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

[Brunan]

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

 

[RupertW]

How and when are you thinking of recharging them?

 

[Brunan]

How and when are you thinking of recharging them?

With shore power primarily and from running the main engines.

 

[Portofino]

http://www.frigomar.com/catalogo-frigomar/FRIGOMAR_Air_Conditioning.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 .

 

[MedMilo]

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!

 

[rickp]

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.

 

[Croftie]

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

 

[Brunan]

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.

 

[Croftie]

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.

 

[RupertW]

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?

 

[jfm]

So on shorepower you use 3 phase only for AC? Is the 40amps at 240v correct?

40 amps at 240v single phase is ballpark correct for 60000 btu/hr airco at full load. You’d normally take that as a single phase dock supply. Boats are wired to take 3 phase from the dock at say 28 metres upwards. But below that size many boats with 60k btu/hr a/c will take a single phase supply from genset or dock and then convert to 3phase on board using a VFD, to power the a/c compressor motor.

Not sure if that answers your Q, so just saying.

As others have said, this much a/c can’t feasibly be done without a generator.

 

[Bouba]

Anyhow, at the boat show I came across thermowellmarine.com who had their Air Jet 12 on display. It’s a 8,800 BTU/h 12v DC unit. Now I realize that this is not powerful enough for you (60,000 btu) but it was running off one moderately sized wet leisure battery. So could scale up. At full pelt it draws 85 amp hours. So it won’t run all night without a recharge. But it shows anything is possible

 

[Portofino]

Anyhow, at the boat show I came across thermowellmarine.com who had their Air Jet 12 on display. It’s a 8,800 BTU/h 12v DC unit. Now I realize that this is not powerful enough for you (60,000 btu) but it was running off one moderately sized wet leisure battery. So could scale up. At full pelt it draws 85 amp hours. So it won’t run all night without a recharge. But it shows anything is possible

10.5 A gets 42, 000 btu or 16 A for 60,000 “ full pelt “ with this kit .
http://www.frigomar.com/images/PDF/FRIGOMAR_chiller-inverter-DC_eng.pdf
I have the 42 ,000 unit and not mentioned here it’s silent a big plus . It’s Eco function ( once chilled ) is only 3.5 A .

Std measurements for my 14.5 M boat came to near 30 K btu so with a 42 K max I don’t think it ever gets near it’s “ full pelt “ 10.5 A
You can never have enough AC in the Med .

 

[Deleted User YDKXO]

At full pelt it draws 85 amp hours. So it won’t run all night without a recharge.

I'm tempted to say whats the point then? Are you going to set your alarm clock for 3am in order to start up the generator in order to save your batteries? Or is there some kind of system which switches the unit off when the battery voltage sinks below a pre set level? I could see this unit being useful for cooling the master cabin overnight on say a 100ft yacht which is likely to have enough battery capacity but yachts that size tend to run one of their generators all night anyway

 

[Bouba]

I'm tempted to say whats the point then? Are you going to set your alarm clock for 3am in order to start up the generator in order to save your batteries? Or is there some kind of system which switches the unit off when the battery voltage sinks below a pre set level? I could see this unit being useful for cooling the master cabin overnight on say a 100ft yacht which is likely to have enough battery capacity but yachts that size tend to run one of their generators all night anyway

Well, I’m not here to defend the product but the bloke said that it’s to get the room down to a comfortable temp then turn it off. As Porto says, over spec everything then it never runs at full draw on your batteries. The smart charger could turn on your genny or have lots of batteries and lots of solar. I don’t know, it’s not for me.
But I was very interested in their DIY model, which was all self contained, 16,000 BTU hours. Supposedly easy to install. But you might need a couple and then will it be too noisy?
Porto’s inverter technology aircon (nothing to do with battery inverters) looks good but is nearly £12,000 for a 42,000 BTU hour model plus installation. So it’s expensive

 

[Deleted User YDKXO]

Well, I’m not here to defend the product but the bloke said that it’s to get the room down to a comfortable temp then turn it off.

Well yes it should be temperature controlled but youre going to be asleep and youre not going to know whether its switched itself off and youre not going to know when it starts again in the morning because you'll still be sleeping off Lord JCB's plonk. In any case, if it works like my aircon does, when the cabin reaches a preset temperature, the air handler for that cabin switches off but the compressors for the chiller unit still keep cutting in intermittently to maintain the chilled water temp. So a big question for me would be does the whole unit switch itself off when the cabin reaches a preset temp or just the air fan? If the former, then yes if you set a reasonably high temp, you could expect to leave the unit switched on for 8hrs and still have serviceable batteries in the morning

 

[Deleted User YDKXO]

But I was very interested in their DIY model, which was all self contained, 16,000 BTU hours. Supposedly easy to install. But you might need a couple and then will it be too noisy?

Possibly. The reason that most aircon systems on boats are separated systems with the chiller compressors in the engine bay and only the air handlers close to the cabins is because the compressors are noisy. With self contained units I'd want to be sure that the noise from the compressor doesnt disturb my sleep otherwise its a bit pointless fitting the units. Many years ago I owned a Fairline Targa 48 and Fairline chose to fit cheapo crappy self contained HFL aircon units in each cabin space with the unit for the master cabin being installed directly under the bed. It was so damned noisy/vibey that it was impossible to sleep in the master cabin with the aircon unit switched on

Just out of interest what kind of system does Beneteau fit to your boat had you specified it from new? That would be a good starting point for your considerations

 

[Bouba]

Just out of interest what kind of system does Beneteau fit to your boat had you specified it from new? That would be a good starting point for your considerations

Yes, it would. At present all I know is that it’s 34,000 BTU hours. The problem is, on a long production run they sometimes change suppliers. There is a new ST35 on a pontoon close to me, it looks fully loaded, I could ask the owner. But that would involve talking to strangers so it probably won’t happen

 

[Deleted User YDKXO]

But that would involve talking to strangers so it probably won’t happen

And in French too so thats out

 

[Bouba]

And in French too so thats out

I was doing well at the boat show talking French to the Italians