Solar Options

I have just returned from an amazing 12000km trip on the Canning & Gunbarrel with mates! Awesome. Now back to less adventuous trips with the wife but determined to do some free camping to christen the bush oven!! I am fairly new to this so in need of advice. Given that I can run heaters and fridges on gas, what is the best solar setup for the rest? I am thinking of having portable panels that can be directed to sun so: are some brands better than others, do I just wire it up so I plug it into the van's connection, how big should I go (150?), and should I get fixed of flexible? Very subjective questions, but I need to start somewhere. Opinions?
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Reply By: Member - Frank P (NSW) - Wednesday, Jul 24, 2013 at 15:45

Wednesday, Jul 24, 2013 at 15:45

How long is a piece of string? :-)

Before we can help we need to know a bit about your setup and your power needs.

What 12V appliances will you be using, how many amps or watts do they draw, and how long will you use them each day?
You have a gas fridge, so that's a biggie out of the way.
What about things like an inverter for charging camera batteries, phone, laptop?
Camp lights?
Do you have a van or camper? How long will you be running the internal lights each day?
How big (in amp-hours) is the van or camper battery?

My first guess is that with a gas fridge your 12V power needs are going to be pretty modest, so you may only need a smallish portable system, but it depends on how you use your gear. Give us a few details and we'll take it from there.



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Follow Up By: Member - Chris_K - Wednesday, Jul 24, 2013 at 16:35

Wednesday, Jul 24, 2013 at 16:35

As Frank said - you first need to know what your draw in Amps is going to be. For example a 120W solar panel will give you 10amps (in a perfect world) which is 120W / 12v = 10amps. So if you have a 100 amp hour battery is should take 10 hours to charge...with the emphasis on "should".



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Follow Up By: Member - Andy T2 - Wednesday, Jul 24, 2013 at 16:53

Wednesday, Jul 24, 2013 at 16:53
I see what you mean! I have a new Captiva diesel and Jayco Discovery. The van has its own deep cycle battery which recharges during driving and is good for a a couple od days depending on what I pull out of it. The van fridge is 3 way as is a separate fridge I will take with me. I have a small inverter to recharge phones, ipads, ipads as we go. If we stop for 2-3 days to freecamp I guess I need to run lighting (it is a new van with LED), radio, and other small appliances which don't pull too much.) I would not want to run aircon, microwaves, etc as I know how power hungry they are. I am not sure what kind of battery came with the van so I guess that is important.
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Follow Up By: Member - Chris_K - Wednesday, Jul 24, 2013 at 17:27

Wednesday, Jul 24, 2013 at 17:27
Another option is a DC-DC charger, which can re-charge your batteries faster. Alternatively, there is some useful info here:

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Follow Up By: Gronk - Thursday, Jul 25, 2013 at 20:50

Thursday, Jul 25, 2013 at 20:50
A dc-dc can re-charge faster ???? really !!

You sure you didn't mean the other way round ??

In my case, I now run a 140W panel mounted on the roof rack of my 4wd......with ability to hinge up at approx. 25 deg..

This way I can park the van in the shade and leave the 4wd in the sun..
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Follow Up By: Member - Chris_K - Thursday, Jul 25, 2013 at 21:26

Thursday, Jul 25, 2013 at 21:26
Yep - DC/DC a quick Google search on DC-DC chargers or perhaps the thread below:

They work pretty well - and they work when there is no sun...! So yes, they do charge faster!
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Reply By: Sand Man (SA) - Wednesday, Jul 24, 2013 at 18:34

Wednesday, Jul 24, 2013 at 18:34

You should see reference to the Solar Power article (top right) which will answer most of your queries. Having got a broad understanding of what is available to suit your circumstances, you could then ask more specific questions to obtain more detailed info from many of the forum members.


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Reply By: Member - Frank P (NSW) - Wednesday, Jul 24, 2013 at 19:57

Wednesday, Jul 24, 2013 at 19:57

I'll jump in with a few thoughts...

Let's just assume a van battery capacity of 100 amp hours.

You need to be aware that there is every chance that your van battery is not being fully charged while you drive UNLESS

1) You know that at the van battery there is at least 14.2 to 14.4 volts under load while the car is running. The chances of this are not very good as (a) generally the standard caravan factory wiring is notoriously inadequate and that will pull the voltage down, and (b) late model vehicles tend to have quite a low alternator output, down around the low to mid 13s in voltage,


2) You have a dc-dc battery charger in your van to boost the low voltage from the car. Van manufacturers do not supply those unless you ask for them. Even then they need heavier than standard wiring, which again you have to ask for.

I assume that Jayco have put a mains charger in the van so that every time you hook up to power you will get a full charge. But if my suspicions are correct, when you're on the road and free camping it is quite likely that your battery is never more than 80% charged from driving, probably less.

Obviously that gives you less capacity on a day-to-day basis if you're relying on charging from the car. It will also cause premature failure of the battery in the long term due to sulphation. Think 18 months (plus or minus) instead of four or five years, though regular top-up from the mains will offset this.

You can correct all of that with decent cabling (for a simple setup such as yours, minimum 8 B&S, preferably 6 (NOT mm commonly used in the auto industry, I mean gauge - 8 or 6 B&S or 8 or 6 AWG) from your vehicle battery to the rear of the car and again from there to the van battery. You should use a separate connecter such as an Anderson, not a spare pin in your trailer plug - they can't take the large cable or the current required. Then, depending on the output from your vehicle alternator, you may or may not need a dc to dc charger.

Sorry to digress, but that's your starting point, mate. I had exactly these issues with my Avan camper and a Kia Sorrento, followed by the same camper with a Toyota Prado.

Now for the solar - well I reckon that's relatively easy.

Assuming a 100 amp-hour battery and given the rough description you've given of your modest 12V useage, if it was me I would use a portable 120watt panel set-up. I suggest portable rather than fixed so you can park your van in the shade and chase the sun with your panels. Two 60's or three 40's fold up into a reasonably compact package for transport and storage.

If your panels come with a regulator on the back, bypass that and run about 10 metres of maybe 5 or 6mmsheathed twincore from the panels to a quality regulator which should be as close as possible to the battery.

Bear in mind that the rule of thumb says you will only get about 70% of your panel's nominal output on average (see the articles on solar referred to by other posters), so out of your 120 watt panels expect about 84 watts ON AVERAGE. However on good days you will get close to ideal output, so your electronics need to be able to handle that. A decent 15 amp multi-stage PWM regulator (around $100 to $150) would suffice. But you'll get more from your panels if you can stretch your budget to a multi-stage MPPT regulator which will increase efficiency to about 97%, or about 82 to 115 watts depending on conditions - about $200 to $250 for a 15 amp model.

Reputable brands will cost about this much, but in both cases there are much cheaper options on eBay, etc.Shop carefully.

My thinking may be on the conservative side, but I can guarantee you that in real life you will not get 120 watts from a set of nominal 120 watt solar panels.

In terms of charging my batteries, the best I ever got from 240 watts of panels and a PWM controller was 100 amp-hours in a long, clear but cool, windy sunny day. (Cool panels work better than warm ones.) Mostly I get about 70 to 80 amp hours (Sunny days are usually warm to hot; as a result panels aren't as efficient.) With your 120 watts you can halve those figures to 35 to 40 amp hours a day which I estimate would meet your requirements.



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Follow Up By: Member - Andy T2 - Wednesday, Jul 24, 2013 at 21:31

Wednesday, Jul 24, 2013 at 21:31
Much obliged, Frank. That's given me much to think about and I am appreciative. The members in this place are amazing! Thanks again!
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Follow Up By: Member - Frank P (NSW) - Thursday, Jul 25, 2013 at 11:31

Thursday, Jul 25, 2013 at 11:31

I just reviewed a bit of what I wrote.

10 amp reulators would be sufficient for 120 watt panels, so that will save a few $$$.

I have just looked up some wire size calculation tables. For a 10 metre run from panels to regulator (that's 20 metres return, you have to consider both +ve and -ve), the 5mm option in the underlined "sheathed twincore" link in my post would be sufficient but the 6mm would be better.

It's a compromise between practical cable size and cost vs keeping electrical losses to a minimum.


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Reply By: tazbaz - Thursday, Jul 25, 2013 at 16:54

Thursday, Jul 25, 2013 at 16:54
Based on our experience using gas for the fridge, cooking, heating and a lighting* and a 100 amp hour battery for a led light and a small inverter for phone and laptop charging we can bush camp for 12 days easily without the need for any solar panels. Water is the constraint for us - not power.

* Two 9kg gas cylinders for fridge and cooking and a separate 2kg gas cylinder for light and heat
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Reply By: landseka - Friday, Jul 26, 2013 at 10:24

Friday, Jul 26, 2013 at 10:24
Andy, as an indication from our system, we also have a 100A/h Fullriver battery in the van. There are 2 x 120w panels on the van roof which supply all charging to the van. There is no connection between the car & van battery.

We have led lights in the van, 3 way fridge on gas when camped, 150w inverter for phones/ cameras etc. We have a 12v VAST satellite tv box plus 22" HD Led/Lcd tv also running direct off 12v.

We rarely have a problem watching tv til 10.30 - 11.30 at night and we never let the battery get below 12.2v. If it has been cloudy & the tv doesn't go on, so be it!

As the previous poster said, water is the limiting factor, not power.

Cheers Neil
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Follow Up By: Member - Frank P (NSW) - Friday, Jul 26, 2013 at 18:57

Friday, Jul 26, 2013 at 18:57
Yes, Andy, it is possible that with your modest power needs you might be able to not bother with upgrading your charging system from the car. Just accept what it will give and use solar to make up the difference and to live with.

If you do that I think you will need an MPPT regulator to make sure you get the most out of your panels.


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Follow Up By: Member - Andy T2 - Friday, Jul 26, 2013 at 22:06

Friday, Jul 26, 2013 at 22:06
Much appreciated to all of you for your replies and advice! Regards
Andy & Cheryl (new 'kids' on the block)
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