Installing Solar Panels on a Motorhome or Caravan

Installing Solar Panels Correctly on your Motorhome or Caravan

So you have decided to install solar panels onto your caravan or motorhome – great! Here are some important tips that will help you to get the most out of your expensive solar panels.

Wiring size

Take care with the size of the wiring. Using cable with not enough copper will seriously affect how well your solar panels will work.

There are a number of reasons why people fail to install panels with appropriately sized cables…

  1. Auto electricians and manufactures of cable for automotive use take a different (and not very useful) approach to specifying cable sizes. For example, if you purchased a length of 6mm cable from an auto electrical outlet, it would fit through a 6mm hole (ie its outside diameter would be 6mm). This clearly tells us nothing about the amount of copper inside that cable. If it has thick plastic insulation – then clearly it has less copper and is therefore able to carry less current before an unacceptable amount of voltage drop becomes likely.  On the other hand a household or industrial electrician will provide a cable that has 6mm2 (that is 6mm squared) of actual copper. This is a useful description of the cable and can be used to calculate the current carrying capacity of that cable.
  2. When you ask an auto electrician or auto electrical retail outlet for “a length of 10amp cable” – they will offer you a length of cable that will carry 10amps without melting. There is no consideration given to how much voltage will be dropped over the length of that cable – thus it is another useless way of specifying cable size.

The correct way to select a cable for solar installations:

  1. Calculate the maximum current that the solar can provide in full sun (use watts divided by volts – eg 120w panel @ 12v = 10amps)
  2. Measure the total length of cable from the solar to the battery – now double this figure (because there are two cables – (positive and negative) that the current must travel over).
  3. Now work out the voltage drop over this length of cable using the following formula

Voltage drop equals (cable length (in metres) X current (in amps) X 0.017) divided by cable cross-section (in mm.sq).

Example – you have 2 X 200w panels and want to connect them  to the battery bank that is 9 meters from the panels – you are considering a cable that is 4mm sq of copper.
200w divided by 12v = 16.66amps – this is about the maximum current for each of the two panels.

18 (two times 9m) X 16.66 X 0.017 = 5.09 now divide that by 4 (mm sq copper) – this tells us that we will have a voltage drop of 1.27 volts. The highest acceptable voltage drop is 3% of the supply voltage (so in a 12v system,  0.36v). Clearly our 4mm cable is far too small.
For this installation we are going to need length of cable that has at least 16mm sq of copper in each conductor for each panel. That is a sizable lump of cable!

As in interesting note – you would need just 4mm of copper if you were installing the same panels on a 24v vehicle – just one reason why I suggest that 12v is NOT suitable for larger vehicles (where the cable length is an issue).

One last word on wiring … while you are running the cable for your new solar panels, consider running an extra cable or two. You may think you have enough solar now but experience has shown that many people add extra panels at a later date – much simpler to do if the cable is already there!

Mounting the Panels

Solar-on-roof

Take a look at the photo of the roof of this caravan. These panels were installed by a person professing to be a “professional solar installer”. Both poly-crystalline and mono-crystalline solar panels decrease their output as the cell temperatures rises. Thus it is clearly important to keep the panels as cool as possible – not an easy thing to do with something that has to be exposed to the full sun. Air flow plays an important part in keeping the cell temperature down and it is for this reason that all manufactures of these types of panels specify that the panels must be mounted in such a fashion as to allow cooling air to flow beneath the panels. There is not going to be a lot of air flow on the underside of these panels.

Mount your solar panels so that there is an air gap of 75mm – 100mm between the panel and the roof or your caravan or motorhome.  If you have selected the far less efficient amorphous type panels (and why would you?) – this air gap is not necessary (because these panels perform slightly better are they get warmer).

Got a question about solar power on a caravan or motorhome?  Got an issue with yours? Or have you really got a great system that you would like to tell us about? Why not leave a comment in the reply box below – we would love to hear from you.

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47 Responses to “Installing Solar Panels on a Motorhome or Caravan”

  1. john Says:

    hi there gav
    almost ready to get solar panels for bus
    done as u said 24v
    so whats best?
    2x12v panels
    or 24v panels

    im thinking
    24v
    if i loose one 12v panel iv lost 2 panels?
    im looking at putting 800w on roof
    and can get 80w 12v panels for 260 each
    so 10 panels
    they are shade tolerant

    but what specs should i be looking at on panels
    like cut off voltage etc
    and does this differ from 12v to 24 v panels??

    on another subject
    i never heard back from that compan y about the inverter
    lost cause
    but i will be taking it up with ebay

    any way safe travels to u and tracy

    cheers
    john

  2. Hobo Says:

    Generally 24v panels are a little cheaper per watt (they are used in large grid connect systems – and thus more of them are produced). When I look at panel specs, I normally look for a “voltage at peak power” value that is a close as possible to my system voltage.
    Example:
    200w Panel #1 has a VPP (voltage at peak power) of 37v. In my 24v system I calculate that it will produce 5.405 amps at peak (200 / 37 = 5.405)

    200w Panel #2 has a VPP of 34v. This should produce 5.88amps at peak (34 / 200 = 5.88) – slightly higher than the output from panel #1 when connected to a 24v system.

    Cheers

    Gavin

  3. Andrew Jackson Says:

    I need clarification?

    In the example above am I correct in assuming that each of the 200w panels has it’s own cable to the (12v) battery?

    In other words if the example above only had one 200w panel 16mm2 copper would still be needed?

    Is it fair to say if the two 200w panels (in parallel) used the same cabling to the battery at least 30mm2 of copper would be needed?

    cheers
    Andrew

  4. Hobo Says:

    I see the reason for your question and I have updated the article to make it more clear.
    The short answer is yes – the calculation is for EACH 200w panel.
    30sqmm of copper will produce a voltage drop of 0.34v (or 2.833% of 12v) when asked to carry 33amps over 18meters.
    Many people consider that it is ok to ignore the voltage drop of the return (the negative wire) if it is connected to the chassis of the vehicle (and thus half the length of the cable for the purpose of the calculation). I feel that this is generally NOT a good plan for solar panels in a mobile situation – also many solar regulators control the negative and in this case you can not connect the panels to the chassis at the panel end.

    Gavin

  5. john Says:

    hi there guys

    firstly the reason behind the question
    as u know i had a iberter failure , not due to my doing .is in your other section
    so i now have 2 inverters.one for appliances one for fridge

    thus giving me added protection of back up for fridge( the main item in any home)

    so now to the question
    i intend useing around 800w solar/8 batteries@225 amp

    if i use one regulator pl40 and it fails ive lost all solar?

    can i split into 2 400w and 4 batteries???
    and run 2 regulators

    thus still having the abiltiy to have at least some power

    i dont like splitting systems ,but im thinking back up

    i dont think running 2 controllers woudl work(confliction??)

    but i think with the amount off batteries it would work with split system

    swicthing fridge to second bank isnt a problem.but id have to monitor closer as not to drain one bank below acceptble level

    system is 24v
    and fridge is 240v ac 130w

    which i think would use about 1000w a day running

    but if there is no prob then both banks are still charging indevidual

    my aim is to make it fool proof , which is some time not the best

    cheers john

  6. Hobo Says:

    Hi John,

    Coming from the IT industry I understand the desire for redundancy. However my advice would be NOT to split the battery bank and solar. So long as they are correctly and robustly wired the PL series regulators are a picture of reliability. Worst case – you can by-pass the regulator and manually monitor the battery voltage and disconnect the solar when the batteries reach peak voltage.
    Splitting is a bad idea for the following reasons…
    1. What if one bank is full and the other empty – one half of your expencive panels are doing nothing
    2. You will never get full use out of your battery bank and you will shortern the life of the most used bank.
    3. Connecting two banks of batteries together when they are not equally charged can cause very high currents to flow between them – this generates heat, can damage the batteries and will result is a loos of energy.

    My recommendation would be to put all panels through the same regulator and connect all house batteries together into the same bank.
    (I would also recommend a low voltage fridge based on a Danfoss compressor – but that is a different story)

    Hope this helps

    Gavin

  7. john Says:

    now how did i know u say that about the fridge lmao
    well im willing to sacrafice the solar for the fridge
    theres enought going up on the roof to do that
    and if my fridge dies
    its easier to replace than a 24v in any major town
    but thats another story
    ok see ur point about solar
    im a mantance manager wirth big company
    and as such i need back up fast
    is my whole way off thinking
    but i agree with u
    i didnt want to spit system
    i just wanted to know if it was a good idea or not
    every thing on the bus is done ,over board as to say
    wiring all heavier than needed
    i donttttttttt wana do things twice
    your web site is very helpfull
    and have learned a lot
    and some off your simple things you talk about gets me thinking more
    which is good
    ive found its always good to toss idea’s around .and hear others idea’s

    well the bus is almost finnished inside
    engineers cert thursday 22nd july
    then rego
    and then hope fully a few short trips

    read ur article on buy bus from start or already done
    well i agrree
    im lucky
    i have heaps off acces due to my job
    and im still going after 18 mnths
    but from srcatch well. its not for those who think its simple
    cause its not
    i have spent upward s of 15k and ive save about 20k doing what ive done
    but the out come is looking good
    any way’s

    maybe see u on the road next year
    we intend leaving .before next winter
    get dam cold here in southern highlands

    kk safe travels

    cheers john

  8. john Says:

    hi again
    ok ordered 6 x80w pannels
    4 x225ah deep cycle batteries

    adding more as money becomes avaliable

    pl 40 on the way

    regadring shunt ?? is there a specila cable for the pl 40??

    or is just wires from shunt to pl 40?/// im putting shunt in negative line

    ok now the part i need to know

    what to hook up in what oreder>>>

    pl 40 to batteries
    then add pannels one at a time???

    24v so in series

    everthing will be fused

    and longest run from solar pannels to pl 40 is 5 mtrs

    and if u got time

    any tricky settings on pl 40???

    thx

    john

  9. Hobo Says:

    Hi John,

    You need a shunt adapter to attach the shunt to the PL40 (PLS1 – I think it is called). This attaches to the PL40 via a RJ11 plug and a telephone wire.
    The shunt can go in either the +ive or the -ive battery line.

    Remove all fuses, then wire and check everything. Once you are sure it is all ok, put the battery fuses in first then the solar fuses.
    The PL40 comes with a good diagram – follow this and you will be fine.

    Make sure you have set the PL40 to 24v.
    Nothing tricky on the PL40 – just make sure you set the correct program for the type of batteries you have.
    Be sure NOT to overload the PL40 load terminal (5a max).

    Gavin

  10. john Says:

    hi again guts
    ok all sytems go
    solar up 6 x 80w so far..another 4 comming
    batteries in 8 x 225ah 6v 450ah@24v

    turned on 6 am
    by 8 am already put 6 amps into system according to pl 40

    question is

    if i want to use my charger in times off no sun

    do i put on same terminals as solar imput ,, so pl 40 will see amps in>???

    and if i do will this hurt pannels

    i have put isolation swiches on each set off pannels
    thus making it easier to check them indevidually if theres a problem
    and to isolate them if needed

    cheers john

  11. Hobo Says:

    Hi John,
    Do not attach the charger to the PL40 solar input terminal. This should be attached directly to the battery system (via the shunt). Because the charge from the battery charger passes through the shunt, the PL40 will take this charge into account in its reporting of the battery state of charge.
    The PL40 will not control the charger (you should use a smart charger that controls its self) – but it will take the charge into account.

    Cheers

    Gavin

  12. john Says:

    hi
    brain drain time
    ok had it right
    showed 20.5 amps charge from charger
    this is before i finaly hooked up solar panels
    and also showed the amps out from the fridge @5.2 amps
    now ive hooked the solar in line
    i left the fridge running all day
    the solar imput started about 12 amps
    and dropped off to 4 amps as the day went on

    im asuming the solar is putting more in then the fridge is using??

    so cut back. as baterries went full??
    since bringing the solar on line
    i have been to this point.unable to get a reading on the usage

    where as before i was??

    so tomorrow i disconect solar and see what happens
    see iff i get the readings back

    seems oddd. before i hooked the solar up i was getting reading off amps out
    i even went to load ext . which is suppsed to be actual real time usage
    but nothing

    ok keep u posted

    cheers john

  13. Hobo Says:

    I suggest you look again at the diagram that came with the PL40 – be very sure that everything is wired exactly as shown in the diagram. Any change from this diagram will cause issues with the readings on the PL40. Look closely at where the shunt is in the diagram AND where the load and charge cables connect to the system. Make sure that nothing other than the shunt is connected directly to the battery.

    Gavin

  14. john Says:

    ok
    after a brain drain day
    4 hours and checking everthing,,, tripple checking

    u wouldnt belive the problem

    THE JUMPER PIN HAD FALLEN OFF THE SHUNT ADAPTOR

    thus putting it in slave mode

    so easy to miss
    ok all running good

    15.8 amps going in from solar 6 x 80w pannels @24v

    fridge 4.5 amps going out @24v

    thanks for ur help
    may see u on the roead some where

    we going away next week for weekend run
    see how it goes

    say hi to tracey….wish her luck with doctors

    cheers john

  15. Hobo Says:

    Thanks John – Glad to hear all is working well.

  16. Len Says:

    I have installed 2×200 & 1×120 panels on my motorhome.Wired individually to Buzz bar.then to a Matson regulator.Im not sure I am getting the maximum from the system.Should they be wired in series or do you think it wont make any difference

  17. Hobo Says:

    Hi Len,
    If the system voltage is 12 volts (as it probably is) and assuming the panels are all 12v panels, then wiring in parallel is the only option (unless you have a very fancy MPP regulator).
    If you do not think you are getting the most out of the panels have a look at my article on testing solar panels located at http://hobohome.com/news/?p=446

    Cheers

    G

  18. Janette Scott Says:

    Would like to know the best way to wire 4 Kyocera 135w panels for 12v. They will be setup on the roof with all the junction boxes at the same end towards the side of the bus. The cable to connect all the panels and travel down to the batteries one way is approx 4.5m. I was considering using 6sqmm to connect panels and then run 10sqmm from last panel to the batteries. What is your opinion?
    Thanks

  19. Hobo Says:

    Each panel will generate about 8amps max (135w/17v). 4 X 8a = 32amps total. If wired individually you should use 4mm cable for each panel (using 9m length (2 X 4.5)). If wired together on the roof and a single cable down to controller/battery consider 16mm of copper. 10mm cable is too small – it will produce a voltage drop of 4.08% – too much.
    Be very sure that the cable provided is actually specified in mm sq of copper – not all are. Automotive cable uses a useless “total diameter” measurement.

    Cheers

    Hobo

  20. Johno Says:

    What a great site, very informative. Thanks a lot. My question is: I have seen a lot of panels fitted straight on to the roof as shown above, so I did the same thinking this was the right way. If I remove it and mount it above the roof say 100mm would not the wind drag under the panel be sufficeint to break it loose ? Your thoughts please

  21. Hobo Says:

    Hi and thanks for the comments on the site.
    You are correct in your comment that lifting the panels up does allow wind to get under them. This simply requires them to be securely attached.
    All of our panels (some have been up there for 9 years) are attached by folded aluminum sheet. This sheet is glued/sealed and riveted to the roof of the bus.
    I do think about the panels when a road train goes past at 110kph – but it has never been an issue. Before you pull up the panels to provide the air gap, I would suggest getting a hold of the technical specs for the panels you own and looking at the temperature coefficient. From this figure you should be able to estimate the advantage in installing them correctly and decide if it is worth the effort (I suspect it would be).
    I hope this helps.

    Gavin

  22. John Says:

    Gday i must say what a great little site i have been reading all over the net about solar i had a set up years ago and had no problems now my new set up is a real pain here is my problem
    I have 2x 120w panels on the roof of my van in parallel they are then fed down to the pv charge regulator a Manson SBC 7120 the run of cable from the panels to the pv reg is about 1m i have made it as short as possible.
    From the charge reg to the 2 brand new deep cycle 95 Ah agm batts connected in parallel the cable is about 500mm in length and good for about 300Amp.
    Heres the problem, the whole time i have had this set up i have never seen the batt voltage above 13v i tested the panels open circuit voltage and it was about 18.5- 19v 9 dident check amps so cant say.
    I have tried every conceivable setting in the pv reg and it has made no difference a friend interestingly enough has a very similar set up with the same pv reg as mine but a 150w panel and looking at the display on his pv reg it always reads around 16- 18v mine reads pv output 12.2 or sometimes 11 volts even on a hot full sun day!
    This is drivin me insane, i can disconnect the neg off the batt where it goes into the pv reg and reset the unit and when it boots up again it looks like it works and displays the pv output as around 18v or whatever, it then cycles through its status about 4 times then the voltage drops back down to 12v or so shown for pv output? its crazy.
    I have heard all sorts of remedies to fix it from chuck the reg and feed the panels straight into the batts which i think is a no no, personally i think the pv reg has had it.
    Anyway any help would be greatly appreciated as this is really beginning to get to me.
    Thanks John

  23. Hobo Says:

    Hi John,
    Voltage is not a good indicator of system health. You need to measure current.
    To test the panel performance you need to do a short circut test.
    1. Disconnect the panels from the battery and regulator
    2. Connect the positive and negitive of the panel set together and measure the current in full sun – this should be close to the rated short circuit current (about 15 – 20 amps) – if it is not, then the panels are faulty.
    3. Discharge the battery a little by leaving a light on at night
    4. Connect the panels (in full sun) to the battery bank (not via the regulator) and measure the current flowing – this should be close to 15 amps or more for a 240w system (don’t leave it like this as it will overcharge and distroy the batteries)
    5. Now reconnect the regulator and measure the current from the panels – if it is less than the reading without the regulator, the regulator is either faulty OR incorrectly setup.

    I hope this helps – please let us know what you discover.

    Gavin

  24. John Says:

    Gday

    Thanks for the reply Gavin i put my meter in line with the panels when disconnected from reg and batts it shows a reading of 5.17 amps @ 21 volts in full sun which is not good.

    I reconnected everything back up and the pv reg tells me the panel current is 5.1 also so the panels are faulty and not producing a decent current at all.

    These are the exact panels i brought here at this link http://cgi.ebay.com.au/240w-Solar-Panel-12-24v-Folding-Kit-Caravan-Boat-4WD-/180664877274?pt=AU_Solar&hash=item2a107740da

    It seems to be one thing after another and im about to chuck the lot and buy a gennie.

    Thanks for your help appreciate it.

    John

  25. Hobo Says:

    Be sure to test the panels right at the junction box to eliminate the possability of cable issues upsetting the readings. Also test each panel individually. Don’t give up on solar!

  26. John Says:

    Gday

    Yes understood Gavin its just a bit hard to get under the panels on the roof i made sure i mounted them correctly they are mounted on stainless threaded rod 50mm above the top of the roof so air can circulate the thing is i cant take them off unless i cut the rod because the rod and spring washers/nuts etc are cut into the mouldings in the ceiling so it is all neat.

    Anyway i am onto it as to what the problem is and the answer is right here http://forums.whirlpool.net.au/archive/1640946 here http://myswag.org/forum/index.php?topic=6066.msg88575;topicseen and here http://forums.whirlpool.net.au/archive/1544832 and so on and so forth.

    But …………… that’s ok as the domain name lhpsolarpanelscam.com is available and i just love making websites with some good SEO work i think i should be sitting just underneath them on page 1 of google i wont bother asking for a refund as the lies will just make me even angrier to unproductive.

    Thanks for your help anyway Gavin i have some work to do.

    Cheers John

  27. Hobo Says:

    WOW that is really bad news – Let this stand as a warning to ALL – beware of scams.

    Thanks John

  28. Ray Says:

    Hi I had 2 x 80 watt panels installed ontop of my caravan and have just recently arrived home from arkaroola where the roads were pretty good just corrugated in a few ares but not too bad only to find my 2 panels with 50% of the crystals broken. Am wondering if you have a method of roof install that will prevent this from reocurring cheers Ray

  29. Hobo Says:

    To be honest, I have never seen or heard of broken crystals on panels. I wonder if you would mind sending me a photo of the panel (showing the break) along with details of the brand and where you purchased them from.

    Panels made by Unisolar are amorphous and manufactured from polycarbonate bonded onto a stainless steel backing (no glass) and are indestructible. The big downside is that they are very large for a given output wattage.

    Cheers G

  30. Ray Says:

    Hey Hobo will get pictures up when I can but since had mate look at my mount system & he reckons a very poor mount system is probably it’s cause just the same I need to find a video or site that shows the correct method of r/v installation as obviously the way mine was installed was hopeless

  31. Darryl Says:

    Hi Gavin,Tracy
    My Question is I have 2 solar panels 1x120w and 1x240w on my bus but Ive had no choice but to parallel connect them as when it comes to hooking these to my solar regulator I can only fit 1 positive wire and 1 negative wire into it .Ive tried running two separate wire runs but there is no way it will fit so would it be better to go out and buy another solar regulator splitting these 2 panels but connecting them to the same battery banks As Ive noticed when i first connected the 240w panel to the 120w panel it made no different reading on the regulator .regulator is Manson sbc-7130 and there is no shunt on this model
    Wire size is 6mm (4.59mm) that joins both panels together and runs 7 metres to solar regulator .Do you know a way that i can run 2 runs of wire as when you twist 4.59mm x 2 this is Hugh wire for a small hole or could I trim half the wire where it goes in .Thanks Darryl

  32. Hobo Says:

    Hi Darryl,
    I understand the issue and it is not an uncommon one. Because the issue with voltage drop is a factor of copper size and distance – one solution would be to bring the large cables into a strip connector very close to the regulator, and from the connection take a smaller wire to the regulator. So long as the smaller wire is not too small and is quite short (say less than 300mm), the voltage drop across this smaller wire can be ignored. I do exactly this with my setup as I have 5 X 4.59mm cables coming down from the roof.
    I hope this helps.

    Gavin

  33. Mike Mercer Says:

    Am considering wiring 2 x 60w portable solar panels in series to give 24v output and charging 12v deep cycle batteries using a MPPT regulator.

    In theory this should give better performance in situations where panel output is low (eg less intense sun or high panel temperature) also would minimise voltage drop over a longer run of cable from remote panels (if regulator mounted close to batteries).

    Do you think this would be an advantage ?

    Many thanks

  34. Hobo Says:

    Hi Mike, In my opinion this arrangement is the only real way to get an advantage from an MPPT regulator. (there is an article on the site about this). Unfortunately most lower cost MPPT regulators do not support this arrangement – be very sure that the one that you select does.
    I have 10 panels on the roof of the motorhome – I would love to be able to series them and feed that into an real MPPT controller. I have not found an MPPT controler with that capacity and function for less than $2000. Would be cheaper to buy more panels :-)
    Gavin

  35. Chris Says:

    Can anyone help me with this, please? I have just bought a smallsh caravan- 4m long, GVM 890kgs. Because I’m not good at reversing, especially into confined spaces, I’d like to be able to tow my van into my double, drive-through garage, unhitch it from my car and attach some ‘go-jacks’, if I were to buy them, to each wheel. In theory I could then just spin it around 180 degrees and push it towards its side of the garage til I needed to use it next time. I did try to rotate it with someone else’s help, with just the jockey wheel recently, and we both strained ourselves big time. Has anyone had any experience in a similar situation with go jacks? I don’t want to spend over $400 and find I still can’t manage it on my own.

  36. Richard Says:

    G’day Gavin, hope all is well for you. I stumbled across your site when i was google searching about Bedford motors and bus maintenance as we were looking at purchasing a bus/motorhome. We are letting the bus idea go for a while as what we want, will take time to build or find and of course the cost is holding us back too..!! In the short term we have opted for a popup caravan and i am planning on setting up a adequate solar system to run an 80lt Engel, a few lights, a decent stereo (love my music), and laptops, chargers etc.
    Thankyou for a terrific, informative and helpfull site. Your technical articles will be of great assistance to me when sizing, building and installing my solar system. If you can make a plumber understand electricity, you could teach physics to a rock, WELL DONE..!!
    Regards
    Richard

  37. Tom Dowse Says:

    Hi I have 2 existing 125w solar panels at present Question is can I add 1x 120 watt different brand panel in series with those two I have a 30 amp regulator already
    Thankyou,
    TOM

  38. Tom Dowse Says:

    Hi, can I add in series 1 x 120amp in panel of a different brand to my existing 2 x 125amp panels

  39. Hobo Says:

    I think you meant to ask..
    “can I add in PARALLEL 1 X 120 WATT panel …”
    Answer – yes, no problem so long as your controller can handle the extra panel. It will need to be rated at at least 30amps.

  40. Gary Says:

    Hmmm…so now the time comes to figure out the mounting. On a 1993 Toyota Coaster, the roof line is curved so my question is where can you buy good sturdy mounting (adjustable?) mounts to suit 200W panels to be installed on the roof.
    I see the ‘glue’ on variety and that is not what I want to do. fastening to through the roof to the metal roof beams is preferred.
    Anybody done this before?
    Gary

  41. Hobo Says:

    Hi Gary,
    With large panels like this it is very important to mount them securely. They form a big sail if the wind get underneath them and their size make them vulnerable to breaking due to flex. Most hardware stores sell aluminium in various sections and thicknesses – this is ideal for secure mounting of panels. Alternately, I have see Colorsteel flashing used very successfully. Take care not to make traps for rain water as this promotes roof leaks!

    Gavin

    PS – how about adding your coaster and some photos to our other rigs page?

  42. Laurens Says:

    I have been adding 2 more panels to my system which now adds up to approx 600 watts of solar panels….. Will my 30 amp regulator still handle the power?

    The next point I wished to make is about the solar panel angle… I noticed on the roof of the van that dirt has accumulated in the corners of the panels.. A mixture of rain and dust… It seems to me that tilting the panels ever so slightly would mean that even light dust and rain would not collect and dry on the edges/corners… What do you think?

  43. Hobo Says:

    Assuming your system is 12 volts, 600 watts of solar can (at least in theory) produce 50 amps. Even if we discount this to 40amps, it is not going to be kind to your 30amp regulator. Some brands of regulator deal with this gracefully by limiting the solar production to 30 amps (thus making a large portion of your panels ineffective) and other brands just simply burst into flames. Given that neither of these is ideal, I would recommend upgrading your regulator.

    I agree 100% that a slight angle on the panels helps keep the buildup of dirt and dust to a minimum.

  44. Darrell Madex Says:

    Hi I am heading off around assie, thinking of mounting 250 watt panels on the roof ( which solar panels would you recomend?). Just wondering what I would need regarding the approprate inverter, cable rating, voltage metre, battery size. Hope you can help this poor dumb yobbo. Regards Mudda.

  45. Hobo Says:

    Hi Mudda,

    Unfortunately there is no simple one line answer to this question. There are just way too many variables for me to even offer an opinion. Factors that are important include:
    - What type of vehicle – caravan, motorhome, pop-top, camper trailer ??
    - Size of battery bank – how much weight can the vehicle handle?
    - Type of travel (how often driving, how long parked and where)
    - Does the alternator charge the aux batteries?
    - Power usage – type of fridge, other appliances, computers TV etc.

    There are a few other articles on this site that may help –

    The ten unbreakable rules for motorhome and caravan electrics
    Buying Solar Panels (without getting ripped off)

  46. Stan Says:

    Hi
    Found your articles so full of very good professional advice THANK YOU. The panel I wish to use is the semi flexible 200watt one for the reason it does not need any brackets and I hope to fix it to the roof using sigaflex. The question is with this type of panel will have no air gap under as its stuck down is this an issue with heat. In regards to wires do I just drill a hole through the roof and sigaflex a junction box over for waterproofing
    Regards
    Stan

  47. Hobo Says:

    It is dificult to say without seeing the specs on the panel, but it is mot likely that the solar panel you are looking at is of the amorphous type. These do not need to be kept cool (in fact they perform slightly better when hot) – the big downside of these types of panels is that they are 1.6 times the size of other panels for the same output. This is typically not practical when roof space is tight.

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