#99455  by landlubbers
 Wed Sep 09, 2015 9:27 pm
Hello, we have recently bought a motorhome which we intend to use for freedom camping (not attached to a power cord). It has a 85 watt solar panel already on the roof, however we do need to upgrade as we know this will not be enough power. I notice a lot of motorhomes are using 160 watt up to 200 watt solar panels. Does anyone have this size fitted and is it enough to run their 12 volt fridge, a tv, lighting, water pump etc? Most of these items in our campervan are relatively new, and our in house battery banks are 110 Ah each and are brand new. I have been in touch with two different solar panel retailers today, however the information is totally conflicting, so I would rather hear from someone who is using this set up and can give me an opinion. Thanks, Grant
 #99456  by Derb
 Wed Sep 09, 2015 10:14 pm
Hi Grant. A whole host of information on this forum re; solar/batteries/regulators etc using search engine. 80 watts plus 100 a/h battery just doesn't cut the mustard nowadays given the toys we use. Our Jayco had the same setup and unless we had perfect cloudless sunny days we were always going backwards battery storage wise. Generally speaking more solar is batter than more battery and nowadays 200 watts of solar isn't really that much. Like I said though - grab a beer, sit down at the computer and start poring over old threads. Cheers.
 #99461  by muzzanic
 Thu Sep 10, 2015 7:03 am
Yep, Derb is right.

There is a lot of different opinions out there, It really comes down to a few things like, are you wanting to just make do or do you want a system that doesn't have you worried you are going to run out of power all the time, Will you be using it all year around ?

Also if you don't want to worry about running the motor or ever plug into power to top up the batteries ( some people move every day & get away with much less solar ) But if you are wanting to stay put for a week in winter, It takes much more.

Your fridge would Like a 250w solar panel & then work out what you need for everything else :o

With out really having any idea what needs you have, The smallest amount that I would go on the road with is 500w solar & 200 A/h battery.

What you can get away with over summer you would need double the solar over winter.

Hope this info gets you started.

Murray
 #99462  by Mark
 Thu Sep 10, 2015 7:53 am
muzzanic wrote: Your fridge would Like a 250w solar panel & then work out what you need for everything else :o
Although, as has been said, you really have to work out what you need for your own situation.
For example, we have a 85L compressor fridge and from our experience (with that) would alter the above statement to:
"Your fridge would Like a 100w solar panel & then work out what you need for everything else :o "

As you can see, it's horses for courses: summer vs all year round, what size fridge, what else will you have running, what will be your average overnight drawdown (in amp hours)? A bigger battery will then give you a bigger buffer (to some extent) for when you get some days with little or no sun).

PS I learnt all this by reading the forum - lots of good information here if you are prepared to spend time reading :)
 #99467  by Neddy
 Thu Sep 10, 2015 8:52 am
Grant, from the little you tell us it is not possible to calculate how much solar power you need and guestimates are bound to vary widely. To narrow things down a bit, we would need to know :-
How big is your motorhome?
How many people will normally be on board?
Do you have any auxilliary charging from the vehicle's motor?
If so, is this a "smart" system, or does it simply parallel the House battery with the Starter battery whenever the engine is running?
What is your existing total House battery capacity?
Do you have a battery monitor fitted? (Do you know what your average nightly battery drawdown is)
What size is your fridge? (It is presumably a compressor model, not a 3-way running on 12 volts)
Do you intend to use the vehicle a lot in Winter?
Do you live in or intend to stay in the NZ deep South for any length of time?
Do you anticipate motoring every day? Every second day? Once a week? Once a month? How much?

With answers to these questions, we can all start giving you intelligent, informed estimates, rather than guesses.
Inevitably, opinions will differ and this is only to be expected. Nevertheless, I think you might well find that a broad consensus will emerge.

Just to get you into the right ballpark, here is our setup :-
7 meter bus.
2 people.
85 litre compressor fridge.
Average nightly battery drawdown usually around 35 Amphours.
We have 300 watts of solar power and 200 Amphours of battery storage. I set up our electrical system over 8 years ago and have had no cause to change anything. Do keep in mind, though, that solar power cost $9.42 per watt back then and you really did NOT want to fit more than you needed. Prices today can be as low as $1/watt! Should it ever be required, we do have high-efficiency charging from the motor, but normally this is never needed. We have a good "3 season" setup, but it is not quite enough for a deep-south Winter without turning on the auxiliary motor charging. Our motoring averages out at about 1 hour/day.

I would see your situation as being very similar to ours and as such, consider that you should view 300 watts of solar power as a baseline minimum. With solar panels now being so cheap, you may as well install more than that, but I cannot see any point in going any higher than, say, 500 watts. Our 200 Ah of battery storage seems to be exactly right for us. We have never found this to be insufficient and there would be no point whatsoever in our paying for more capacity than we need. As it is, we have a "4 night" power reserve which we have never fully drawn on.

Go for 400 - 500 watts of solar power. The actual figure will be decided by the panels themselves and where you can fit them. Concentrate of avoiding any shading. A good, shadeless 300 watt system will outperform a 600 watt system that is partially shaded.

I would be interested to know what the two solar panel suppliers recommended you get.

Neville.
 #99468  by muzzanic
 Thu Sep 10, 2015 9:04 am
Although, as has been said, you really have to work out what you need for your own situation.
For example, we have a 85L compressor fridge and from our experience (with that) would alter the above statement to:
"Your fridge would Like a 100w solar panel & then work out what you need for everything else :o "

As you can see, it's horses for courses: summer vs all year round, what size fridge, what else will you have running, what will be your average overnight drawdown (in amp hours)? A bigger battery will then give you a bigger buffer (to some extent) for when you get some days with little or no sun).
100% Agree & I was throwing out there what a fridge can get through, All be it in winter & allowing for weather that isn't great.

IMO the answer is so complex that most if not all people, Can't work out what they need, Given that no one can work out what Rain/ cloud cover/ Sunlight there is going to be to charge battery's, Let alone look into the future & work out how long & where we will be staying in the years to come :D

I was making the point that even 160 to 200w isn't a lot.

If we hit a Newbe with most of the little things like not all panels are created equal,

The type of glass that they have & there ability to stay clean,

The size wiring that is used both before & after the controller, So as to not have to much voltage drop.

The thousands of controller's out there in the big wide world, That are not created equal & don't charge the battery's the same way or the same amount for a given panel size, The charge voltages of multi stage controller's vs the one's you can't set.

All this without getting into battery size & type, Wiring size & length, voltage drop to the fridge, Inside & out side temp of the camper etc.

Then this for all the other things we use.

There would have been a heart attack involved :o

We do however know that the deeper stage of discharge we take our battery's the more life we take out of them, ( Once again depending on what type of battery to what effect it has )

The more solar you have the sooner in the day that the solar can hold it's own & stop the discharge of the battery, Lowering the depth of the discharge the battery, So there for not taking as much life out of the battery.

How deep people are ok with taking there battery's down to is up to them, As at the end of the day it is them that has to pay.

Given that bigger solar panels IMO are cheaper than bigger battery's, I will always choose to go for what some people would call over kill on solar, So I can get the best out of a bad day.

But as you have rightfully said, Everyone has different needs & it is up to them to work out what they are.

Murray
 #99471  by Teardrop
 Thu Sep 10, 2015 9:22 am
I think over analysing this will confuse the OP. That first post is a bit confusing as to whether there are two 110 a/hr batteries, or just one. I read it as two.

Basically, the solar capacity will determine how fast your batteries charge when you are stationary. The battery capacity will determine how long your system can last without charge.

The roof will have a bearing on how much solar you can fit without shading the panel's.

Both battery and solar capacity will be more important if you are staying longer periods stationery. If you like staying in shady areas (e.g. under trees) then battery capacity will assume more significance.

So how long is that piece of string? My experience is that if you already have two 110 amp/hr batteries, then the more solar you can put in , the more peace of mind you will have. Especially in winter. So if 200 watt is your limit, go for it. If you can find a way to put 300 watt in, I'd recommend that. The price difference will be small, especially with a single panel as labour costs to install will be little different between small and larger panels.

Dene
 #99474  by Roamnz
 Thu Sep 10, 2015 11:17 am
Landlubbers, let the 'search' button near the top of the page next to the home button, be your friend. This will get you started, then coupled with much of what Neddy -Neville has mentioned above will give you ideas of what questions to ask next.

We have 4 x 120 panels (480w) and that works for us coupled with 2 x 260 amphr AGM batteries, a 45 amp Morningstar Mppt solar controller, a Votronic battery monitor and a Xantrex 1800 pure sine wave inverter. We would class ourselves as heavy power users, when we were full time on the road for many years. We use a nespresso coffee machine, a washing machine, an 800w toaster, a slow cooker, hairdryer when needed, our fridge is a three way 174 litre Dometic. All our power points can be run as 240 when our inverter is switched on. We carry a 2kva Honda generator but that is very rarely used, only then we have been stationary for four or five days with very little or no sun, mid-winter down south. The generator spends most of the time gathering dust in the locker, but there as a backup.
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