This article is the second in a series, if you have not read "Calculating how big your battery needs to be." I suggest you read it first, as it explains a lot about batteries and how they should be set up. There is already a lot of information out there, but our articles are directly related to RV's and the Australian situation. The article will expain how to get more from your batteries by either supplimenting the charging with solar or going for a complete solar system.
Not everyone who reads this needs a full system, I will cover the basics first.
Above: Glass Solar panels have been around the longest and offer the best solution in household and commercial installations.
Above: For mobile applications the semi-flexible panels offer some advantages, but generally at a more expensive price.
Above: Folding panels in both glass and flexible are very popular with Campers due mainly to the ability to move them around to catch the most sunlight.
A solar panel is a grouping together of individual solar cells to produce an electric current. The electric current leaves the solar panel and goes through a solar regulator then into a battery. While you can run a 12V appliance or light directly from some solar regulators, a more basic setup connects everything to the battery.
Above: A single panel generates around 17 to 19 volts. The solar regulator then reduces that voltage to a suitable charging voltage for your battery.
Multiple panels and batteries can be connected to a single regulator but that will be discussed later.
A solar panel is made from solar cells. Different solar cells can produce a different number of watts from a given surface area. This is particularly important for the limited mounting surfaces available on a Caravan or Motorhome.
As detailed above, the cells can be bonded to glass or a semi-flexible base. The temperature of the panel surface can effect the output also. This is a reason given to support the use of raised glass panels. While I have not tested the difference in output in identical circumstances, I chose a flexible panel due to the weight reduction, durability, and ease of cleaning. The cost was only marginally more after the price of mounting brackets was added to the glass panel cost.
Fixed panels are extremely convenient and more secure from theft compared to portable panels. Portable panels allow for maximising solar capture by locating and pointing the panels directly at the sun. Theft of portable panels can be an issue particularly if leaving the campsite unattended. You also need to allow storage space for portable panels that are packed up and not operating during travel.
A panel that can be fitted to a roof during travel and only removed when setting up in a shaded position is also a real option.
The specifications of a solar panel will indicate the output voltage and output wattage. Solar panels can be joined together to give additional wattage output at the same voltage.
Remembering from above, a solar regulator controls the voltage that comes from the solar panel to what the battery needs to charge correctly.
The solar regulator will have a specification for the maximum number of amps it can accept from the solar panel(s). Adding the total number of amps from multiple connected panels will give the minimum sized regulator you need. Don't skimp on this, as many people decide to increase panel numbers or size after a while. Another reason not to cut it too fine is that solar panels can actually exceed the quoted output in ideal conditions, especially in full sunshine but cold ambient temperature.
Another important consideration is if the solar regulator can vary the output to maximise the battery charging like a multi-staged battery charger. This allows faster battery charging at the beginning and float charging to get the battery up to 100%.
Some other features that a solar regulator may have are:
Some solar panels come with MC4 connectors which allow for easy waterproof wiring. We also sell the easy to add connectors. There are adapters available that permit joining two cables to one. An easy way to add any number of panels to the one set of wires. These provide a perfect junction for testing if a fault occurs.
Many people install solar panels by cutting the connectors off and soldering, but troubleshooting problems is easier with the connectors in place.
The instructions that come with the solar regulator will identify the wire thickness required depending on your distances, but RV applications normally use 6mm square UV stabillised wire connecting your solar panels to a solar regulator. The same thickness wire can connect the regulator to the first battery. When connecting batteries together you are advised to use premade battery leads available through automotive parts suppliers. If you have a large inverter, say 2000w, you would also connect it with battery leads to the battery bank.
Many people love their first solar panel and the free power they get, so they decide to upgrade. It is an easy upgrade if you have the space.
Above: 2 panels (or more) can be connected in parallel (positive to positive) resulting in the same Voltage, but double the Watts. Also 2 or more batteries can be connected together in parallel to double the storage capacity. Having 2 or more batteries allows larger inverters to provide 240V for equipment like microwaves.
An example installation may have 4 x 100 watt panels, that produce (4 x 5.5) 22 amps. This is within the capability of a 30amp regulator and will give a healthy charge to your battery bank.
Above: This diagram represents a more comprehensive 12volt/240V system that is very functional and would meet the requirements of most Caravans and Motorhomes.
a) A battery charger will be used to charge your battery(s) when 240volts are available.
b) A multi-stage charger is best, plus the higher the Amperage output of the charger, the faster it will recharge.
c) When the sun shines, the solar panels will feed a current to the solar regulator.
d) The solar regulator will first try and supply current to any 12volt devices (f) connected directly to it.
e) Any excess current from the solar panels will go to the batteries to recharge them. The batteries can accept charge from a battery charger and a solar regulator at the same time.
f) While 12volt lights and devices could be connected directly to the batteries, the better solar regulators will prevent over-discharge of your batteries if you connect the devices to the 12volt load terminals provided on the regulator.
g) Most installations will now include an inverter, which generally gets connected directly to the batteries. The inverter produces 240V that you can connect any **240v appliance to.
**Warning: Do not connect your battery charger to this 240v outlet. Specialised switching is required to input the 240v back into your 240v circuit.
For more information on how many panels and how many batteries you need, see "Calculating how big your battery needs to be."
Dealing with Caravans Plus is a plus. Prompt delivery all products fully documented and website second to none with information available on it. No matter where in Australia I might be I can go online and get an item within a few days. Terry G, Perth, West Australia.
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59 Comments
Rod
Well presented good valid information
Terry
solar panel 200w out put 19.95 v it is going through 12 dcdc charger is this right thing to do?
ShedMan™
Awesome info here but could you please explain if the solar panel to regulator should be fused to prevent damage in the unfortunate event of a short circuit, Also should the output from regulator to battery/s be fused?
Mike
Solar panels are the only things that cannot short themselves out. Don't know why but they don't.
Dave
I personally DO use both inline PV fuses and 40a breakers. Comes down to 'prevention before cure' ..... NO harm in running the extra protection for the cost of a few bucks ;)
Christina
Very informative. The diagrams also help explain it more.
Jim
Aux and battery low wiring
Simom
Can I then run a power lead from the inverter into the 240v input on the caravan so my whole van is powered?
Smitty
Safety and legal wise I have no idea . But I do know it works and works great . Been doing it for years . My inverter has a kill switch though .
Martin
How could you possibly run a power lead from an inverter to run the 240v of the caravan? Unless of course the battery is not connected to a 240v charging device. Otherwise, you would have a massive loop.
Graham
Yes the inverter would not be plugged into 240v but connected to the battery.
jason
Did you get a answer to your question would love to know the answer
Mike
You could do that I suppose but you will have to have a lot of batteries to keep everything running.
Dave
I AM doing exactly that with my caravan mate. I have 2 x 250 watt panels into my 40a Renogy Rover and then out to my 2 x 148ah batteries. I currently have my 3000/6000 watt inverter connected to my lead battery and from the inverter, I run an extension outside the caravan [battery bank and inverter in fire proofed enclosure under my bed] which then plugs into the 15a caravan power plug. Just NEVER have mains/shore power connected while you have the inverter connected. You CANNOT run the inverter + mains/shore power into the caravan input at same time. Hope you understand. .
Darren
Having multiple outlets powered off an inverter ( they actually have two different positives out of phase) could be very dangerous if there is any fault with the wiring( or even worse multiple faults) don’t do it.
dennis lourigan
I found the info very helpful, plus the diagrams, good on you
Graham
No mention of MPPT solar controllers and their greater efficiency over PWM type. Also MPPT controllers are far superior if panels are connected in SERIES. Greater input voltage reduces need for heavy wiring with lower voltage loss over longer leads too. More sophisticted in operation for a greater output. Unfortunately somewhat more expensive.
Leon
I have 2 200 watt panels volts going up to 17 volts what regulators do I need
Stephen Hope
2x200W=400W Max Voltage stated = 17Volt W/V=A therefore 400/17= 23.5Amps but to be safe 400W/12V=33.33Amps so a regulator capable of 35Amps would be more than sufficient to handle the power of your system.
Ian
I'd like to add an extra solar panel to the roof of my van. Due to best mounting position & way of routing wire from extra panel to the existing solar regulator (TPS1230), wiring would need to be approximately 8 metres long. will this cause a problem with voltage drop. Should I install another solar regulator closer to the new solar panel. Both solar panels will be charging the same battery.
dj wizard
suitable directions
Rodney
Very informative just what i wanted to read Thank You
Geert
In most diagrams their is no earthing to chassis just like the above ("Full Solar System with Inverter") is that fine or do you need to earth just the AC or DC or Both to chassis
John
Very good info. I'm wondering if I have a dodgy cell; I connected my cell as per your simple setup. I turned the fridge on to battery to check cell output. 19V at the regulator terminals which dropped to 12v with fridge on. . The fridge draws 13 amps. The battery was measured as suppling 12 amps, the cell to battery 0.6 amp. Any ideas?
Chris
Is a 200w solar panel compatible with a 20 amp solar controller & a 130amp battery?
Tony
200 watt panel pulls about 11 amps max.
Rob
What glue or tape is used to fix flexible panels to motorhome & is an air gap required. How is that done?
Sash
As far as I know, you should have an air gap for the cells to run efficiently in higher temperatures (and prevent the diodes from failing in high temperatures!). You could look at an insulation layer such as a honeycomb board underneath, not sure how flexible this is though. I have stayed away from flexible panels because of those issues.
Leanne
This might be a stupid question.... can you charge the batteries from a petrol generator.... I’m thinking yes but are there any special things to know?!? Cheers
Sash
You sure can Leanne! You connect to an AC/DC charger to do so.
Kim
Ive heard generators are not the best way to charge batteries. They will get you up to 70% but then are overpowered to slow charge the rest of the way. Not very efficient.
Robert
Do you have a wiring diagram for having a DC to DC charger in the circuit with solar and the solar regulator?
Mark
Hi I have 3 x 250w solar panels with a voc of 22.3v I have a 60a solar controller and two iTechworld 120a batteries, the batteries are in parallel. The question is should I wire the panels in series or parallel and what should the batteries be wired in series or parallel Thanks and looking forward to your reply Mark C
Michael
You have a lot of solar for 240Ah of battery - I have 450w for 280Ah. I think 750w / by 12 x by .85 is the required max battery charger/regulator. = about 54 so your charger is correct. If you connect batteries in series you double the volts - like 24v, 2 batteries in parrallel doubles the Ah, 2 batteries in series doubles the volts
Here is what u don't won't to do, and I found out the hard way, connecting the solar on the same terminals as the lights and tv, if u take off a battery terminal when the sun is out it will put high voltage to your TV and lights and in my case the tv blew up, solar has to be connected on the second termanils or isolated in some way from the power to your appliances , when u disconnect from the battery the power will go up at least 5- 10 volts and if anything is turned on boom as I found out
James Nathaniel
I've a 2018 Jayco Penguin, can anybody tell me if it is possible to connect solar panels to the tow hitch anderson plug, will they charge the battery via the BMPRO J35 battery management system as if it were connected to the vehicle or must the solar panels be connected directly to the battery bypassing the battery management system?
Mark
I don't know about the caravan but I connect my 180 watt solar panel to my cruisers Anderson plug that was set up for my caravan fridge and it charges my cruisers second battery OK , I'm with you , does it work on the van side ?
Smokey
As a sparky, this is the simplest, best explained way to set up a solar system I've read about. I always get these questions and some people find it difficult to understand what I mean. Now I just refer them here. Thank You.
Mike R
I can't position my Regulator any closer than 4 meters from the battery in my caravan... is that to far? I have 2 x 100ah batteries, and 2 x 300w panels.
Bill Seibright
Hi mate, I have a caravan with 360 watts of solar, my regulator is a solar charge controller 12/24v, my question is how do I set it to 12v? after installing the unit I was putting out 19v at my volt meter , need to change it down to 12v the controller values are all above 26v on the screen Cheers Bill
Velesh
Hi , What sort of set up will be ideal to run a normal electric geyser 9 using solar power - Will the below work _ 2 x 300 watt solar panel _ controller _ 2 x 200ah batteries _ 1 x 5000 watt inverter
david
hi, is it okay to have solar panels via a regulator charging a 12v battery on a caravan with a 240v battery charger permanently wired in so when arriving at powered sites and plugged in the battery charger will start charging the battery? or could having both the solar and 240v charger connected at the same time damage the battery or regulator/charger? thanks
Michael
That is what I have,
Josh
Might be a VERY silly question but for a complete NEWBIE I have to ask. If I want to sent up my Van to have 240v outlets (like normal ones around your house) that I can plug multiple things into. Do I simply need an inverter and then an electrician to come in and wire the 240v stuff up? Just not sure how to get the power from the inverter to the 240v outlet in the wall that's all? (sorry if its a stupid/obvious questions)
Narelle
in our van we have a battery charger and also have solar. Do you leave the battery charger turned on always or only turn it on when on 240v.
Michael
You need a solar regulator/battery charger for the solar to batteries and a 240v battery charger to charge 240v to the batteries.
Lenna
Hi, I would like to know if DIY solar system for a campervan is possible in Australia or needs to be done by a certified engineer?
William
I have a new Bailey caravan. Is it fine to run a set up like this (or one of the fold out eBay ones that come with a regulator and alligator clips) and just clip onto the battery? Can I continue to keep using the caravan electronics while the panel is charging?
kratika
I appreciate the Complete Guide To Installing Solar Panels for this piece of useful information. solar panel installation Austin is providing the same services in the Austin city of USA.
Vince
Bit of a newbie on Solar Regulators and appreciate the great wiring diagram. I am wondering about having the Solar regulator output and the battery charger output connected together. i.e. There are effectively two power supplies feeding into the battery so wondering if there is any risk of damage to the Solar regulator or Battery Charger where their respective outputs also become an input, fed from the other device. I know in other types of circuitry a "Diode" is installed to prevent this type of electrical backfeed. Love to hear some feedback on this.
Michael
Your 240v supply goes to a circuit breaker, from there to a 240 outlet switch - like in a house. you plug your battery charger into that, then from b/c to the batteries.
Keith
Is it OK to have the solar panel charging at the same time as the towing vehicle from the alternator? Should the solar panel have an isolating switch?
TREVOR
I have just replaced a 100 watt panel with a 250 watt panel, I have 6 mm wire 7 meters in length will it be big enough?
Michael
The equation is 2 x the length x total amps of devices x .0182 / by .36 2 x 7m x 20/??? x .0183 / by .36 =
Michael
That is 2 x 7 x 17/??? x.0183/.36 =12mm2 wire, not 12mm wire. You need 6BNS OR 6AWG WIRE/CABLE
Energy Renovation Center
Nice I got great help by reading this article !! Thank you so much for this amazing article !!
Warren
Hi, I use your products and they have all worked well - thanks. I am not handy with tools to say the least. I am now interested in fitting Solar to my van for a BIG and know very little about the systems and seek your advice please. Assuming I will off road for say 5 days what type, make of system would you recommend to fit: * one big unit say 350watt plus or 2 x 200watt or 2 x 150 watt * do I need a second battery in the van - I currently have two batteries in my cruiser, one directly feeding the Van * approx costs * do you know who fits the system and cost in the Hills area of Sydney I need to start somewhere please. - help
Ian
Hi, a very informative article. I have a camper van fitted out with twin 120 Ah AGM batteries. It has a 12V "cigarette" lighter outlet at the rear to power our plug in hand held shower. This setup is sufficient for up to 5 days of camping as long as you arrive at the campsite fully charged, which has not been an issue travelling around Australia. But with shorter trips since Covid we have been arriving at camp with these batteries not fully charged, so a portable solar panel to top up is now on the agenda. My dumb question is; can this solar panel be plugged into the rear 12V outlet directly, rather than attaching to the batteries as all the wiring diagrams imply?
Graeme
G'day guys n gals, Under the latest standards ISO 3001 etc... it is required that all wiring is mechanically protected, I am upgrading the existing wiring to meet this standard on my 11' Jayco spite pop top. With solar on the roof and the cables running through conduit and an external junction box & gland into the van, is there a suitable commercially available mechanical protection solution aside from an ugly corrugated conduit running between two junction boxes (1 under the ceilling and the other above the cupboard where the cables are running through a conduit to the MPPT controller & isolator, fuses etc..