Solar on Motorhome

CarolynJCosenza · Member

Solar on Motorhome

yobarr · Guru

CarolynJCosenza wrote:
Hello fellow motorhome owners, Ive recently bought a second hand Jayco motor home. I would like to put on solar panels
how large must my solar be to power the air con. How many batteries would I need

Needs to be BIG. Details later if I find time, but it can be done. Where do you live? Cheers

Whenarewethere · Guru

As already pointed out, very large. Also very large batteries.

Very doable if approached with the right components including a 2.5KW split system.

There is no reason why one needs to go without if you have the space & payload capacity.

There are plenty of threads discussing the technical aspects of this issue.

Cuppa · Guru

It is possible to run air con from solar & batteries but you will have to decide if the cost to do so is worth it. This article may assist.

www.rvpartsexpress.com.au/blog/post/is-it-possible-to-run-your-caravan-a-c-on-battery-and-solar-power/

Some people manage to have air con with less than this article suggests but I believe the reality is that it is only 'part time air con' with an RV quickly re-heating after a couple of hours 'relief'. But still is not cheap.

Other ways of managing heat which cost a great deal less are to travel without air con, but to places when the climate suits, or to spend longer in high temps/humidity allowing your body to adapt to conditions (it does - or at least it has for us)

OR travel with air con & pay for powered sites to plug in to each night - when we had air con in a motorhome our travel costs were much higher - we referred to our air con as our Caravan Park Magnet. If you have it & use it it is very 'addictive'. If it's needed medically then it's needed. If it's a comfort thing there are alternatives.

Fans & maximising airflow through the motorhome help a great deal.

Whenarewethere · Guru

If one uses a typical caravan AC from last century then there is no hope, they are simply rubbish at best. Their energy efficiency is a joke at best.

The current Daikin, Mitsubishi or similar 2.5kW split systems are extremely efficient, have soft start, so no issues as far as batteries or having to have a large inverter. Get over it, I have run an AC off a computer UPS.

The standard caravan AC is equivalent to importing ice to Australia in 1839 from USA. Lazy manufacturing at best. What can a manufacturer get away with!

If used in an eco setting they use very little energy. Often simply reducing humidity will allow one to live like an Emperor in northern Australia.

Dick0 · Guru

Hi Carolyn

As a minimum... 1000 Watts plus of solar panels, 60-80 Amps Mppt solar controller and 400 plus of Amp Hour Lithium (LiFePO4) batteries.

If it is only to run the aircon in your Motorhome then it would be cheaper to get a 2.2KW gennie, similar to a Honda. They are fairly light to handle and quiet.

Safe travels.

Cuppa · Guru

Whenarewethere wrote:
The current Daikin, Mitsubishi or similar 2.5kW split systems are extremely efficient, have soft start, so no issues as far as batteries or having to have a large inverter. Get over it, I have run an AC off a computer UPS.
If used in an eco setting they use very little energy. Often simply reducing humidity will allow one to live like an Emperor in northern Australia.

I don't doubt it could be done, but the question is how much solar & battery would be required to be able to run it enough to be useful in an RV?

The following is very possibly wrong, so whilst I am questioning the ability to live like an Emperor in an RV in northern Australia (fully air con whenever desired) in an average RV, I'm hoping that my assumptions may be wrong.

I don't know a great deal about air con, but assume they cycle on /off much like a fridge, and also assume the 'on' ratio would be considerably higher in the average RV than the average of 50% with a fridge, given that RV's are generally rather less well insulated than fridges.

If they run at 250Kw - that is around 200amps @ 12v so even being generous about a possible duty cycle of say 50%? on that would be 100amps per hour. So running the aircon for 8 hours per day would use 800Ah or more daily plus inverter losses. Say 1000Ah/day So this would require at least ?1200Ah to 1400Ah of Lithium battery storage taking into account the need to run other appliances too.

Then you need the solar to replace lets say, 1000Ah per day when stationary (ie, not relying of driving/engine charging). This would conservatively require approx 3500w of roof mounted solar & a minimum of 5 sun hours per day.

So lets say $10,000 to $14 000 for batteries?, $3k to $4K for 3.5 Kw of Solar? & another $5k or $6 for a 3Kw inverter charger and the cost of the air con itself + fitting (Allow a total of say $25K to be sure, where then is all this stuff going to fit in/on the average sized motorhome? All that solar needs a lot of RV roof real eatate. A split system air con is no small item, the batteries need space as do the rest of the electronics.

If I am anywhere near close to the ballpark on this ..... then the only compromise is a far smaller system capable of only running the air con for much less of the time. Perhaps 2 hours a day? The problem then is whether the user deems it worthwhile to have 'part time' air con, when, in the sort of weather it is useful to have the air con, the motorhome is back to stinking hot a short time after the two hours worth of air con have been used up.

I suppose it's possible that by not turning the aircon to to it's maximum cooling capacity & paying a fair bit of attention to it's operation one could minimise use of power, (& extend running time) but who wants to sit inside a motorhome all day being an air con tweaker & monitor? If it were me I'd sooner just stay at home.

I welcome being corrected (politely) & if so would like to see which assumptions I have made are incorrect & the alternative figures in regard to how much solar/batteries are needed to provide a useful (defined) & sustainable air con system in a motorhome

-- Edited by Cuppa on Saturday 15th of April 2023 10:40:57 AM

Cuppa · Guru

Dick0 wrote:

As a minimum... 1000 Watts plus of solar panels, 60-80 Amps Mppt solar controller and 400 plus of Amp Hour Lithium (LiFePO4) batteries.

Hi Dick0, Do you have air con you run off your system? I expect if you do you must find it worthwhile?

Can you say a bit more about what your usage of air con looks like - ie. for how long & how often & how cool?

CarolynJCosenza · Member

North of Adelaide thank you

TimTim · Guru

Hi Carolyn and welcome to to the forum.

Unfortunately your question is very open ended as it depends on how long you want to run the AC for and what unit you have. I recently did a test on my Dometic Ibis 4 running it from 8.00 am to 5.00 pm and even left the door open. I have 500W of roof panels, 200W of portable panels with 560Ah of LiFePO4 batteries and a 3000W inverter. At the end of the day I had only used 3% of my batteries so 16.8Ah.

Some AC units draw a lot of current to start so what make and model is yours?

Th first area to start would be to look at how much solar you could fit on the roof as you would want to fit as much as you can.

Good luck

Tim

Cuppa · Guru

TimTim wrote:
Hi Carolyn and welcome to to the forum.
Unfortunately your question is very open ended as it depends on how long you want to run the AC for and what unit you have. I recently did a test on my Dometic Ibis 4 running it from 8.00 am to 5.00 pm and even left the door open. I have 500W of roof panels, 200W of portable panels with 560Ah of LiFePO4 batteries and a 3000W inverter. At the end of the day I had only used 3% of my batteries so 16.8Ah.
Some AC units draw a lot of current to start so what make and model is yours?
Th first area to start would be to look at how much solar you could fit on the roof as you would want to fit as much as you can.
Good luck
Tim

The Ibis 4 is rated at 1656 watts when cooling. That equates to around 135amps at 12v. Variables of course are temperature setting & ambient temperature. And then of course how much your 700w of panels were putting out. Essentially if you had only used 3% of your batteries capacity, the sun was powering your air con almost exclusively all day. With 500w of roof mounted panels & 200w of portables by my reckoning if it were possible to get 8 hours of full sun hours in a day the total output wouldn't be much more than 480Ah over that period. An assumption on my part (possibly erroneous) is for a 50% duty cycle of the air con. If so that should, at 1656 amps when cooling for 50% of the time (4 hours ) add up to 540Ah usage. Take the 16.8Ah used battery capacity from that gives 524Ah (in round figures) which is a bit over the 480Ah the solar panels can provide, but in the ball park. I'm working this out as I type, and must admit that it is closer to your results than I thought it would be. Reduce the duty cycle, (cool day, air con doing less work?) then I can see your figures being feasible, but if that is indeed the explanation of your usage figures it doesn't tell the story of how things would be in the hot weather when air con is most desirable.

I admit to having been cynical about your claim, but only on the basis of my understanding (Or lack of) as to how these things work. Thats why I have attempted to work it out & surprised myself, now thinking that it may indeed be possible.

Can you add more info about the variables which would have affected the results? I am doubtful that getting 8 sun hours in a day is feasible, but if it were a coolish day & the air con was only lightly working & if all your panels were able to be adjusted to optimum solar angles throughout the day then these things could be significant.

I realise that you may not have a 12v system - I used that because I understand it, but whatever the voltage, watts are watts aren't they?

yobarr · Guru

CarolynJCosenza wrote:
North of Adelaide thank you

No worries. The reason that I asked is that I have good contacts in several places, including Brisbane. If you do it properly, and DON'T go El Cheapo you can run your whole van, and your AC 24/7, no worries.

My whole van runs off Solar, except for diesel heater, and I have AC, microwave, slow cooker, air fryer, electric frypan, toaster, TV, stereo etc etc and I have never run out of batteries.

AC is 2.5kw Mitsubishi HEAVY INDUSTRIES 2.5kw reverse cycle, and uses little electricity, as does the Daikin recommended earlier by Stephen (WAW).

Have 1650 watts Poly panels, 5kw Victron inverter, 540ah LITHIUM batteries. NO GAS appliances in van.

Dicko is on the right track.

Again I will say DON'T be tempted to buy El Cheapo . After many years selling quality Solar systems I can confirm that a quality Solar system will produce up to 3 times as much power as will an El Cheapo model of the same size.

Anyone who believes the tripe sprouted in TV adverts for Solar Systems is living in La La Land.

Happy to advise good products and suppliers. Cheers.

-- Edited by yobarr on Saturday 15th of April 2023 06:11:46 PM

TimTim · Guru

Cuppa,

To be honest I was completely surprised by the figures and did not at any stage see anywhere near 1656 watts being drawn. I cant recall the temperature for that day but it was quite hot and I set the AC to 23C and left the door open on purpose. For a short period 1270w were being drawn but that very quickly dropped. I know the duty cycle is nowhere near 50% as I had previously did short tests and posted screenshots of the Victron shunt trends on either here or another forum. If I had done the same test today on a beautiful sunny day would I have achieved a similar result? Of course not as the sun is now much lower and the power generated will be substantially lower than it was back in December. But then again I wouldnt need AC on a day like today. Of course there are many factors to consider when running AC and in the end you have to be mindful of the power that you use and the power that you generate.

I will see if I can find the screen shots of past tests.

Cuppa · Guru

TimTim, that's most interesting. Thank you.

msg · Guru

I have really only felt the heat during one time in Mt Isa in my MH. and I was lucky enough to have access to 240v. As said above, it was no fun sitting in the MH with the noise of the AC blasting you in the ear all day.

It was a relief to take time out at sundown to go over to the Buff Club and sit in the cooling air having a nice icy cold drink as the sun went down.

I have lithium batteries but only able to fit 2x70amps. This is plenty for the normal things like, 12v fridge, water pumps, TV, charging phone, computer and running the internet. Given the costs quoted above, maybe you might consider a generator to run your Air Con and one big enough to handle it would be very heavy. However, you won't be popular with the other campers. Might be best to just bite the bullet and go to a Caravan Park when it gets unbearably hot.

I think this would be the cheapest option.

Bobdown · Guru

CarolynJCosenza wrote:
Hello fellow motorhome owners, Ive recently bought a second hand Jayco motor home. I would like to put on solar panels
how large must my solar be to power the air con. How many batteries would I need

Carolyn, forget it.

Apart from the well intentioned posts, you have a Motorhome and not the solar or battery to compete with them.

As msg says, you probably wouldn't use it enough to justify the costs, get a gennie or a few 12V fans and avoid the heat of the day.

Cheers Bob

yobarr · Guru

Bobdown wrote:
CarolynJCosenza wrote:
Hello fellow motorhome owners, Ive recently bought a second hand Jayco motor home. I would like to put on solar panels
how large must my solar be to power the air con. How many batteries would I need
Carolyn, forget it.
Apart from the well intentioned posts, you have a Motorhome and not the solar or battey to compete with them.
As msg says, you probably wouldn't use it enough to justify the costs, get a gennie or a few 12v fans and avoid the heat of the day.
Cheers Bob

Hi Bob. Perhaps you could explain what "not the solar or battery to compete" means?

And, trust me, it's pretty stupid hoping that a 12v fan blowing 45 degree heat on you in an effort to "cool down" when it's 45 degrees inside the van will have a pleasing outcome, while the anti-social gennie is just what we all need at bush camps! Cheers

-- Edited by yobarr on Saturday 15th of April 2023 07:46:41 PM

Bobdown · Guru

yobarr wrote:
Bobdown wrote:
CarolynJCosenza wrote:
Hello fellow motorhome owners, Ive recently bought a second hand Jayco motor home. I would like to put on solar panels
how large must my solar be to power the air con. How many batteries would I need
Carolyn, forget it.
Apart from the well intentioned posts, you have a Motorhome and not the solar or battey to compete with them.
As msg says, you probably wouldn't use it enough to justify the costs, get a gennie or a few 12v fans and avoid the heat of the day.
Cheers Bob
Hi Bob. Perhaps you could explain what "not the solar or battery to compete" means?
And, trust me, it's pretty stupid hoping that a 12v fan blowing 45 degree heat on you in an effort to "cool down" when it's 45 degrees inside the van will have a pleasing outcome, while the anti-social gennie is just what we all need at bush camps! Cheers

If you can't see that a MH doesn't have the roof space or the weight carrying capacity to load up on battery and solar panels as compared to a van, yobarr I'll draw you a picture.

Most MH's only have a single AGM, and that will not run a AC, okay for you as you have a split system AC and the solar to charge NASA.

It's not 45 at night and you would go to a CP and use their power if it was.....Carolyn asked the question and I answered truthfully, not giving false hope.

yobarr · Guru

Bobdown wrote:
yobarr wrote:
Bobdown wrote:
CarolynJCosenza wrote:
Hello fellow motorhome owners, Ive recently bought a second hand Jayco motor home. I would like to put on solar panels
how large must my solar be to power the air con. How many batteries would I need
Carolyn, forget it.
Apart from the well intentioned posts, you have a Motorhome and not the solar or battey to compete with them.
As msg says, you probably wouldn't use it enough to justify the costs, get a gennie or a few 12v fans and avoid the heat of the day.
Cheers Bob
Hi Bob. Perhaps you could explain what "not the solar or battery to compete" means?
And, trust me, it's pretty stupid hoping that a 12v fan blowing 45 degree heat on you in an effort to "cool down" when it's 45 degrees inside the van will have a pleasing outcome, while the anti-social gennie is just what we all need at bush camps! Cheers

If you can't see that a MH doesn't have the roof space or the weight carrying capacity to load up on battery and solar panels as compared to a van, yobarr I'll draw you a picture.
Most MH's only have a single AGM, and that will not run a AC, okay for you as you have a split system AC and the solar to charge NASA.
It's not 45 at night and you would go to a CP and use their power if it was.....Carolyn asked the question and I answered truthfully, not giving false hope.

Hi Bob. Thanks for your thoughts, but even with 1650 watts Solar, 4 seasons hatch and Sat TV you will see that there still is a lot of spare room on my van, which is under 20'. Cheers

Bobdown · Guru

yobarr

Hi Bob. Thanks for your thoughts, but even with 1650 watts Solar, 4 seasons hatch and Sat TV you will see that there still is a lot of spare room on my van, which is under 20'. Cheers

My point exactly yobarr, it's a van not a Motorhome with no roof space to speak of.......read my answer again. Also no storage for 540 amp of batteries.

Aus-Kiwi · Guru

Heat is not an issue to me . By the time heat is an issue I figure the batteries will be charged by say 2pm when its hot . 20 -25 amps here on overcast day .. only the front in low. By the time you have the solar and batteries ? You probably better off with a dare I suggest a generator . The reason I travel is to be in climate that suits me ! South or on the coast in summer . North in winter . Home for me is Blue Mountains or south coast, Culbara beach . Be heading north soon !!

-

-- Edited by Aus-Kiwi on Saturday 15th of April 2023 10:09:51 PM

yobarr · Guru

Bobdown wrote:
yobarr

Hi Bob. Thanks for your thoughts, but even with 1650 watts Solar, 4 seasons hatch and Sat TV you will see that there still is a lot of spare room on my van, which is under 20'. Cheers

My point exactly yobarr, it's a van not a Motorhome with no roof space to speak of.......read my answer again. Also no storage for 540 amp of batteries.

Under the bed. Simple stuff. How big is this motorhome that can't fit 1650 watt solar? Panels are not very big. Where there's a will there's a way Bob. Cheers

CarolynJCosenza · Member

Thank you. Im in my 60s and due some health issues I need an air con

CarolynJCosenza · Member

ha ha Ive sparked some debate I luv it, Im in my 60s and require a reliable air con for health reasons

Are We Lost · Guru

Which model Motorhome do you have, and which air conditioner is fitted? The discussions above suggest knowing the size and air conditioner type is pretty critical to getting a sensible answer.

Does it need to run all night? If it's 40+ degrees outside, how cool does it need to be? Or is it just needed to dehumidify? If you only need to drop a few degrees that makes it a lot easier.

Mike Harding · Guru

Running an A/C in a caravan or motorhome from batteries can be done (Yobarr does it as do one or two others) but for most it is not an affordable or practical arrangement.

I once did a rough cost estimate on Yobarr's full solar installation and calculated it at around $45,000 - he's not corrected me on that so I guess it's in the ballpark and he's also, in addition, had to replace all his solar panels once and, of course, the batteries won't last forever. Then there is the added weight on the roof of the vehicle which may affect handling and/or cause roof issues.

I will shortly be upgrading my caravan solar installation (I am a full time nomad) to a level where it could run an A/C for a few hours but I'll not use it for that because fully recharging the batteries will generally not be possible. I shall continue to use a small Honda generator for those few times a year, in Victoria, when I need AC.

If you have a health condition which necessitates an A/C then you may need to consider whether a motor home lifestyle (or holiday?) is suitable for you.

Whenarewethere · Guru

2.5kW split systems are extremely economical to run. Often in a small space they do not need to be run at their 'rated' output. Let alone on boost, turbo or whatever the manufacturer calls it, or pushing the system to overdrive to about 3.5kW output.

If used in a eco setting, low speed setting or dehumidifying setting a split system is very energy efficient.

You could easily get the system running well less than 500 watts (they are 500%+ efficiency minimum for rated output for current split 2.5kW systems made a decade or more ago).

With 1.0kW solar input, easily doable on a reasonable sized roof. Or add a couple of portable panels if needed. You will have enough to run the air conditioning & also charge the batteries, including running fridge etc.

Chuck out the BS pointless payload so you have enough weight options for lead acid batteries. I reckon you could easily remove 100kg of crap if your priorities are sincere.

Mike Harding · Guru

All noted WAWT and I'm sure modern systems are efficient but nevertheless it still takes X amount of energy to cool a caravan and I don't know what that number is especially given the high number of unquantifiable variables.

However; I do know that a 1200W fan heater will raise the temp. of my van from about 5C to 15C over about 90 minutes so that is probably what would be needed to bring a 40C van down to 30C. I can't be bothered to do the sums but that would be a fair chunk of battery power however I guess if you are in 35C+ you have a fair amount of sun.

However this year, in Victoria, we had a number of 40C+ days and I was camped in forest; unfortunately forest does not make those days any cooler but it certainly reduces the solar capture considerably and no way could I have supported a solar A/C.

My advice: if you *really* want it and you are prepared to spend the money then go for it but make sure you always camp in areas which are fully accessible to 100% sun - which makes things hotter - and don't be surprised if when you are in shade it all falls apart.

However; I suspect that, on forums, we are more often told of the successes than the failures.

Whenarewethere · Guru

One can squeeze blood out of a stone. But if one couldn't be bothered putting effort in for the long term. To their detriment!

Bobdown · Guru

Whenarewethere wrote:
2.5kW split systems are extremely economical to run. Often in a small space they do not need to be run at their 'rated' output. Let alone on boost, turbo or whatever the manufacturer calls it, or pushing the system to overdrive to about 3.5kW output.

If used in a eco setting, low speed setting or dehumidifying setting a split system is very energy efficient.

You could easily get the system running well less than 500 watts (they are 500%+ efficiency minimum for rated output for current split 2.5kW systems made a decade or more ago).

With 1.0kW solar input, easily doable on a reasonable sized roof. Or add a couple of portable panels if needed. You will have enough to run the air conditioning & also charge the batteries, including running fridge etc.

Chuck out the BS pointless payload so you have enough weight options for lead acid batteries. I reckon you could easily remove 100kg of crap if your priorities are sincere.

Sometimes WAWT you are not thinking before you post !! Why would she get a split system and where would she put? when there is already a AC on the roof.

It is a motorhome not a block of flats in Manly, get a grip mate..