12v Aircon for caravan

Submitted: Monday, Jan 06, 2020 at 10:18
ThreadID: 139514 Views:1157 Replies:6 FollowUps:9
I'd like your thoughts on the effectiveness of this aircon. I have a 2 year old van, equipped with 2 x 100ah lithium batteries and 600w of solar. I was thinking of installing it above our bed, where there is a bit if spare roof real estate as a" Bush backup" to the 240v Dometic aircon to save using the genny etc .Weight is not a problem as I have 960kg payload and roof is reinforced for fitting sat dish.

Hi Gerard,
Thanks for your interest.I have fitted a few of these 12V units as we upgrade Vans and Motorhomes for free camping with all appliances working.(no generator needed.)
Solar and 12V A/C work perfectly together as you usually only need air conditioning if the sun is out.
I have just fitted out a Motorhome with my solar and batteries he now has 4 x 395W shade tolerant panels on his roof along with my 3Kw 12V A/C
On a good day I measured 96A going in to his 1040Ah batteries The A/C at full load draws 68A so he had 28A left to run his fridge etc.
This 12V unit is more powerful than most 240V units and draws less power than running a 240V through an inverter.
If you would like to discuss further I am contactable on
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Reply By: Member - peter_mcc - Monday, Jan 06, 2020 at 10:20

Monday, Jan 06, 2020 at 10:20
Do you have any specs on it? Make/model? Website?
AnswerID: 629368

Follow Up By: Gerard S - Monday, Jan 06, 2020 at 10:28

Monday, Jan 06, 2020 at 10:28
No, I only have the above letter from the installer who seemed quite protective of the make and model.
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FollowupID: 904210

Reply By: Member - peter_mcc - Monday, Jan 06, 2020 at 10:54

Monday, Jan 06, 2020 at 10:54
At full load it isn't going to last long - assuming you can discharge the Lithium batteries down to 20% (you would want to check that...) you have 160Ah of battery. At full load that's 2 1/2 hrs assuming fully charged, no solar and nothing else (fridge, etc) on.

68A @ 12V is 816W. If your 600W of solar actually produces 600W (doubtful) then you'd be going backwards at 216W/hr or 18A/hr during the daytime. But your 600W solar probably won't actually produce 600W on a hot sunny day - the output goes down as the temps go up (which is when you want to use your A/C). So you'll go backwards faster.

His solar system is rated at 1580W (395 * 4) or 131A but on a good day he's seeing 96A - or about 75% of the rated power. That would give you about 450W or 37A from your 600W of solar. So at full A/C speed and solar you're going backwards at 31A/hr - the batteries would be flat in 5hrs.

It may be that after a time the A/C ramps down - I'm not sure how much power you need to keep a caravan cool - and so it would run for longer.

My concern for you is that you will flatten the batteries while it's running rather than charge them up. My guess is that it might work for overnight for a few hours when you want a little bit of cooling but don't want to run the generator.

AnswerID: 629369

Follow Up By: Gerard S - Monday, Jan 06, 2020 at 11:04

Monday, Jan 06, 2020 at 11:04
Thanks Peter, I will think through your calculations as I'm not very smart on such things. We were looking at a couple of hours at bedtime etc. I can easily (but not cheaply) increase my lithium capacity. Yes we do run a 220l fridge freezer 24/7.
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FollowupID: 904211

Follow Up By: Member - peter_mcc - Monday, Jan 06, 2020 at 11:08

Monday, Jan 06, 2020 at 11:08
Perhaps ask him how much current it will draw at its lowest setting and what the cooling output will be.

As an aside, all my calcs were done with a nominal 12V - your battery voltage will be a bit higher (13.2v?) which will have a small effect on things. I think your problems are bigger than that though - I think you'll need lots more battery and solar
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FollowupID: 904212

Reply By: Dave B18 - Monday, Jan 06, 2020 at 12:51

Monday, Jan 06, 2020 at 12:51
There is NO 12V air conditioner that will come even close to cooling a caravan. Anybody that tells you there is lying outright.
The 12V/24V air conditioners that are available use the BD80F Secop compressor. They are at best only suitable for a truck sleeper cab, and that is what they are made for. No different to the evaporative coolers, only suitable for sleeper cabs.
The other issue is the 12/24V air conditioners are not at all efficient and are dinosaur technology.
The Mitsubishi Heavy Industries Avanti Series 2kW is 7 star efficient, only suitable for small caravans. 2.5kW up to 17' and 3.5kW up to 21' - as the air conditioners go up in size the star rating efficiency drops slightly.
Have a lot of these running on inverters in RV's, but all with lithium batteries in *correctly* set-up solar systems with excellent equipment, not the usual trash equipment you see people talking about here. If you are prepared to spend the money and do the job properly, life is a dream. On properties using inverter air conditioners on inverters, they have adequate capacity (read 'large')lead acid batteries on 48V systems. You a'int going to do air conditioning in an RV with LA/AGM.

Edit: Quote - "This 12V unit is more powerful than most 240V units and draws less power than running a 240V through an inverter. " That is blatent lies. Nothing compares to inverter units and their 7 star rating.
Would never fit 395W solar panels to any RV. Doubt they would survive long. Shade tolerant - be interesting to know the brand, because don't believe it.
AnswerID: 629372

Reply By: Batt's - Monday, Jan 06, 2020 at 21:55

Monday, Jan 06, 2020 at 21:55
You could by a couple of these they might help to take the edge off a little in a dry region, don't use much power. https://transcool.info/product/transcool-ec3-plus-portable-evaporative-air-conditioner-copy/
AnswerID: 629382

Follow Up By: Dave B18 - Monday, Jan 06, 2020 at 22:54

Monday, Jan 06, 2020 at 22:54
Absolute rip-off rubbish for $319
First and foremost you need low humidity for evaporative coolers to work. Secondly the pad area and volume of air will do nothing even in a small caravan. Evaporative cooler in a caravan would more than likely bring more problems like mould.
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FollowupID: 904243

Follow Up By: Allan B (Sunshine Coast) - Monday, Jan 06, 2020 at 23:44

Monday, Jan 06, 2020 at 23:44
.
You still around Dave?
How about responding to my suggestion in the "How Much is Enough" thread?
Or have the Mods scared you off?
Surely you can do better than just trashing every thread.



Cheers
Allan

Member
My Profile  My Blog  Send Message

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FollowupID: 904249

Follow Up By: Gerard S - Tuesday, Jan 07, 2020 at 10:08

Tuesday, Jan 07, 2020 at 10:08
Thanks for the comments. I'm going to go back to the supplier for more info on make and model etc, plus the queries raised here.
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FollowupID: 904262

Follow Up By: Batt's - Tuesday, Jan 07, 2020 at 12:06

Tuesday, Jan 07, 2020 at 12:06
Dave I did say in a dry region, might take the edge off obviously you've already done an experiment with one 2 know it won't even help a little bit you need to chill out by the way.
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FollowupID: 904266

Follow Up By: Dave B18 - Sunday, Jan 12, 2020 at 14:41

Sunday, Jan 12, 2020 at 14:41
Was looking yesterday for some small brushless low power hydrodynamic or maglev bearing fans on Asian websites and came across many of these small evaporative coolers for under $35.00 and as low as $20.00
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FollowupID: 904404

Reply By: Keith B2 - Tuesday, Jan 07, 2020 at 12:54

Tuesday, Jan 07, 2020 at 12:54
I have 990 watts of thin film solar on my caravan roof with 400AH of lithium batteries and a 1.4KVA inverter charger. On the back is a very small Toshiba split system aircon. Run it flat out and it can easily draw 90 amps from the batteries while it cools the van down.

But put it on "Quiet" setting and choose a temperature of maybe 25 degrees on a hot day and it settles down to 20-25 amps. Run in conjunction with a Sirocco fan, it's quite comfortable. You can't hear it inside the van and it's silent outside a couple of metres away. During the day, the solar will run the aircon as well as charging the batteries.

I looked at a number of 12 volt system for truck cabs. But they are undersized, expensive, inefficient and use old technology.

Keith
AnswerID: 629404

Follow Up By: Gerard S - Tuesday, Jan 07, 2020 at 22:40

Tuesday, Jan 07, 2020 at 22:40
Appreciate your reply. Thanks
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FollowupID: 904317

Reply By: Member - Geoffrey E (WA) - Thursday, Jan 16, 2020 at 13:24

Thursday, Jan 16, 2020 at 13:24
Maybe something like this Close Comfort
AnswerID: 629547

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