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  • New small solar set up for caravan - opinions/advice please!

    I'm installing a small solar system for my caravan - this is my first time working with solar. My electrical experience is mostly limited to diy auto electrical work; I can solder, use a multimeter and have a basic grasp of 'how things work' (think grade 12 physics).
    I've done a fair bit of research but want some unbiased opinions/advice before I get started Budget is an issue in that I don't want to spend on what I don't need, but I'd like to do it right, maintain batteries well and have it all work efficiently and effectively. A pretty long post, trying to be fairly comprhensive; if you stick with me I appreciate it!

    The van is an old 16ft Jayco , the vehicle an 80series landcruiser (1993) with dual batteries. Might just get a solar blanket for the car and its 40ltr Engel, a friend with similar can keep things running for a week no worries. Our travel tends to be very off grid - we very rarely stay at caravan parks and don't want to rely on mains power at all.

    Power usage - low.
    Really only usb ports (2 phones, 2 tablets, not used heaps), limited lighting (2*int+2*ext), water pump for the kitchen sink, and a small inverter to charge laptop, toothbrush, and batteries for power tools very occasionally. Highest draw there is 80w. Probably a blender so she can make smoothies, I've found a nice little one that draws 300w. There's a 3 way fridge which we can run on gas while in camp (90ltr Dometic, 12.5a) and I thought switch to 12v while connected to the car.

    So... here's the idea.
    160-200w in 2 panels, roof mounted in series but removable to chase the sun if we want. I'm leaning towards 2*80w as they fit on a sandwich board and that'd just be easy but 100w mono are cheaper..
    140ah AGM 12v battery.
    20a dc-dc solar charger. I like the idea of being able to use the car to charge after a couple cloudy days, and to get fully charged while driving (assuming solar alone rarely would) for battery longevity. Fair?
    Inverter. 300 or 600w. I actually already have one, but it's at dad's place and he's on the road for another week or so.. and I can't remember what it is. I've figured that a 140ah agm should be limited to a 420w inverter (140/4 = 35a *12v =420 - cheers Sunking!). If I install a 600w but never draw over 420w, I'm thinking that would be ok.....? On the flip side, a 300w blender would likely trip a 300w inverter, right?

    Here are links to the products I'm looking at. Prices are AUD (AUD*.66=USD)
    Battery; decent reviews and warranty, looks like a solid mid range choice at a good price. $267 delivered.
    https://www.aussiebatteries.com.au/b...-cycle-battery
    Charger/reg; any one used the Thunder? At $239 it's $100 less than the Ctek and looks like it does what I need. Haven't come across any complaints...
    https://www.aussiebatteries.com.au/b...harger-thunder
    Panels. These guys have a lot of happy customers and better prices than most. 80w is poly, $85. 100w is mono, $67.
    http://www.lowenergydevelopments.com...lar-Panel-Poly
    http://www.lowenergydevelopments.com...talline-Pickup

    Inverter as I said, I'll know in a week or so.

    I guess I've focused on the big ticket items. I'll also want to put in something pretty simple to monitor things, a voltmeter seems the most obvious way to go, any recommendations here? Maybe an inline watt meter for the panels?

    Wiring and fuses/breakers I'll look at next. Will probably ask a mate with the right tools to do the heavy leads up for the inverter, the rest I should be right with...

    What do we think guys? I figure if I really need to I can go up to 300w panels and 250ah batteries on that controller, but I'm hoping it wont be necessary. We'll be living out of it for up to a year, so plenty of time to figure it out once the base system is together.

    Thoughts, concerns, ideas? Thanks a lot, this forum has already been a great resource.


  • #2
    Just my views. Panels on roof are going to be a disappointment. They never work well as the vehicle is alot of times in shade or the angle is not right. They really are a gimmick I'm sorry.
    I use large portable as you can really target the moving sun and get a decent amount of juice throughout day. The thing about panels is you really need far larger size than you think, most i see outdoors are using dinky little panels. i carry up to 900watts 3x300W for my portable lifepo4 battery box so i can be sure i'm getting it full in places with just a few hours of sunlight. You have to factor in shade, clouds, and in lower latitude areas the amount of sun can be small like victoria in winter. Use a quality solar charger like victron mppt. i would be using a compact fold 200-250w panel for the 4wd and fridge alone. solar blankets are not that practical for long duration (more a quick stopover) as they get blown around alot and end up being a pain. from what i have heard 3way fridges that big are bordering impractical for longstays as they consume too much gas. That dc-dc might be good enough but 20A rate on 140AH capacity is slow and means alot of driving, if you wanna roll into camp fully charged get a 35-40A size. Enerdrive make a great unit that allows custom settings like charge rate.
    I wouln't touch that AGM with a ten foot long pole, nasty. Cheap AGM's are junk and don't last long. Don't skimp on the battery. One usual recommended brand by experienced travelers is FullRiver DC series 120AH. Don't take the whole poly vs mono (solar efficiency BS) too seriously. As long as you have large panels setup right. Sadly most portable camping panels are a joke. They have pitiful leg systems, bulky alloy frame & are still using 17V. That is for caravan parks. In the real bush you need 20-30M long cable runs to find the sun in some places. 17V is unacceptable.
    Voltage gauge on battery terminals direct will give you a rough idea on where you batts are at, but you need to know how to use it. Underload V is different to the voltage seen during charge. I just use underload voltage to get a rough idea when the battery is down to 50% & needs to be recharged, it's usually around 12-12.2V underload. occasionally you can go lower to 11.5V if you need to with small loads like fridges. Inline wattmeters are truley a joke, I have used many & they all stuff up. Stay away & avoid like the plague. If you want to know watts, amps coming into the battery you should get a quality battery monitor like BMV 700series. Really what you find is wattmeters & volt meters are not needed if you set things up right as they dont make any diff to the clouds or panel positioning. With AGM stay above 12V and try your hardest to get the charger to go to float. Simple LED blinking lights on CC will tell you.or victron bluetooth monitoring on phone. As a rough guide I use 5AWG/ 5B&S wiring for running alternator to DC-DC up to 5M length, CC to battery etc. Try keep the length between the CC & DC-DC's output to battery short like 1M.
    Use a basic voltdrop calc to determine the cabling needed between panels and CC. You will see you start to need very thick gauge once your panels are over 10M away from CC input. Most panel kits you buy have small wiring as they think you are camping in a caravan park. Really just better to strip it all away & start clean with quality twincore sized for the distance. If the wireing is too big for yoyur tatste, then you have to start thinking of upping the panel voltage.
    As a rough guide, if your in an area with 5-6hours of direct hard summer sun, a small 300w is enough as you got plenty of hours to finish absorb, even in late afternoon the sun can still provide a large % of panels wattage. more sunhours=less moving of panels. if your in a place with just 2-3hours in winter like vic or Tas you have to oversized bigtime!. Not only is the amount of sunhours smaller, but the total amount of harvest is alot smaller. Take into account shade, clouds, mountains & well you will soon find out...
    I switched from AGM to Lifepo4 so I can recharge in as little as 2.5hours in winter, using massive portable panels. also the cost of quality AGM in Aus is only marginally less then lifepo4 dropins. And by the sounds Chinese lifepo4 is probably going to still last longer than AGM.
    Last edited by Jman; 08-10-2019, 06:50 AM.

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    • #3
      You cannot wire your panels in series with that charge controller. Max solar input is 25v. If you use that one you have to wire in parallel. I would look at a different charge controller.

      Here is my recommendation.

      Since your FJ80 is dual battery I assume you are familiar with battery isolators. I would add a second battery isolator (or one that is capable of charging 3 batteries simultaneously) and wire it ( with the appropriate fuses, wire size and disconnect. I recommend Anderson power pole connectors) to charge your caravan batteries while in tow. Victron makes the argofet that can charge 3 batteries from the alternator. Another option is a voltage sensing relay like the blue sea ACR models.

      For the caravan, it depends on your power usage what size battery you will need. Personally I would go with a minimum of 2 6v golf cart batteries wired in series for 12V. Flooded or AGM your choice. Flooded is cheaper and more forgiving. Size your panels and solar charge controller based on your battery size so you are charging at the C/10 rate. Sunking has a couple of stickies (more like ALL) that are worth reading. Look for a solar charge controller that is mppt and has a high solar input so you can wire in series.

      Panels flat or tilted or removable is a debate that been raging for a long time. Everyones needs are different.
      Last edited by Suprasoup; 08-14-2019, 03:45 PM.

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      • #4
        Right, thanks a lot for the replies guys

        First, the reason I'm having them mounted on the roof is that they have to go somewhere while on the road! Space is limited and the roof is empty.. I will buy mountable panels and make them to be portable (easily removable) that I just won't take down if it's not necessary. I'm currently living in the Kimberley region of NW Aus - lots and lots of sun every day. I'll be traveling through the outback in summer... but also will be in Tasmania in autumn, so will size my panels for that. I can imagine that even low efficiency flat on the roof would be enough in some of my situations, but will treat them as portable panels when I need to... By buying mountable panels I can wire them myself in series for higher V and less drop over long runs, add some sturdy legs and maybe hinges... the option of angling them whilst on the roof is also there.

        re: the battery. Thanks, have done a bit more reading and changed my mind. Spending a bit more to buy a heavier battery with a slightly 'lower' ah rating.

        Charge controller. I've decided that to start, I won't go with dc-dc. I'll still run a wire from vehicle battery (with a disconnect) so that I can plug the 3 way fridge into 12v directly when on the road, and add a dc-dc charge controller or just the isolator plan separately later if I need to. This way I can buy a better solar controller initially and see how it goes...
        I like the Victron 100/20, which looks the right size for me and has bluetooth to give me a fair bit of info. Battery monitor does still look like a good idea, will look into this a bit more... it's a fair bit more money I'm hoping the victron with a couple panels in series will manage 100% charge most days, and gives me the option to add a third if req.

        Also, I can get about 3 weeks straight from one 9kg gas bottle for my 3 way fridge, and carry two, so that should be fine
        Last edited by AussieSun; 08-14-2019, 08:31 PM. Reason: Just missed a couple things

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        • #5
          You are looking at a similar build as mine current build.

          I disagree on the above comment about flat mount are gimmicky. 24/7 exposure instead of only exposed while at rest (setup) far outweighs the alternatives in my perspective - design criteria (esp if one has batteries). Why run off a ICE alternator when on the road when the panels are right there? If you are driving, you are not using loads per se... perfect time for the PV to be powering fridges/etc. In all actuality... finding loads to run off PV during the daylight is my largest issue.

          Increased drag/resistance from an aggressive/bulky frame & racking, not to mention visibility (increased theft risk), is IMHO worse off then flush mount. Measurement would need to be detailed, but yes they'd decrease your gas mileage (as would the alternator powering your fridge, batt charging, etc.), so if you have panels, why not generate with them?

          Curious on fridge selection, given on efficiency compressor>absorption>thermoelectric. But finding a compressor based fridge running on DC at a good price is my problem. I'm attempting at all costs to avoid gas/propane... added hassle/risk IMHO.

          If you are keeping batteries isolated, there are low amp (20) charge controllers specifically for 2 battery banks (unlike the leisure light/load out). But they are only rated to 240 watts... and I was unable to find one larger (so I scraped my 2 batt bank plans). Battery isolation is most important on charging... less so on discharge.

          I opted for no AC (large power requirement), though good insulation, radiant/UV wrap and a solar cooling/water heating system in the roof. [Irritatingly] that is the one system of my build working the best, keeping the panels cool (<43C) and the interior cool also.

          In hindsight, and if space/weight was not a limiting factor, I would start the design with the most PV I could fit, then size charge controller, then batteries.

          Comment


          • #6
            Originally posted by Jman View Post
            Just my views. Panels on roof are going to be a disappointment. They never work well as the vehicle is alot of times in shade or the angle is not right. They really are a gimmick I'm sorry.
            Boy!

            I wish I had known this sooner! I have installed flat mounted panels on three different RV's and thought that they worked quite well.....

            I had better rethink my day today as I was getting ready to go out and start installing flat mounted panels on a fifth wheel trailer in my yard.....


            Seriously,

            I have had good success with flat mounted panels in mobile applications. Yes, panel output from flat mounted will not match portable, tiltable. We can account for that and panel appropriately.

            I am working on a new rig for myself. I travel a bit. Sometimes December may find me in Seattle. I am installing (flat) 6 x 300 watt panels along with a charge controller that will allow me to limit charge current should I find myself in AZ in July.

            There are plenty of us who have had success with mobile applications. Simply account for the reduced output due to less than ideal orientation.



            Comment


            • #7
              Originally posted by PNW_Steve View Post

              I am working on a new rig for myself. I travel a bit. Sometimes December may find me in Seattle. I am installing (flat) 6 x 300 watt panels along with a charge controller that will allow me to limit charge current should I find myself in AZ in July.
              Can you expand on how the CC limits current pls? I am assuming you have a MPPT, but I am curious as to how the CC does this? Are you setting a max battery voltage? Does it start "dumping" extra watts as heat through the heat plates? Does wire size between the CC and Batts affect this? Would wire size provided false readings on Batt voltage to the CC if undersized?

              Just trying to understand how my MPPT CC operates, and trying to decide if I need to upgrade my wire. 40 Amp MPPT CC, <15 ft run from batt to CC (currently AWG12), 12 volt system, 100 watt panels, 2s2p so max amps in is 11 amps and 36 volts in. For some reason I'm thinking (in perfect conditions, from CC to batts the MPPT CC could be pushing nearly 30 amps. Am I wrong, as I'm thinking to upgrade wire to AWG 6.

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              • #8
                Originally posted by PNW_Steve View Post

                Boy!

                I wish I had known this sooner! I have installed flat mounted panels on three different RV's and thought that they worked quite well.....

                I had better rethink my day today as I was getting ready to go out and start installing flat mounted panels on a fifth wheel trailer in my yard.....
                94A7B4CB-DD56-4064-9534-011B8201D600.jpeg7FC21BC0-368A-46B5-AD89-3C4465E2B354.jpeg
                Indeed!
                Probably the only times I wish I made my panels tilt able. And Im not removing the snow for solar generation but because Im not a dick and remove snow off my vehicle before I drive on the road.

                And to the OP. Yup thats my FJ40 towing my Zombie Apocalypse Trailer. ZAT! Both have solar panels on them. The 40 has 2 x 75w panels on the roof rack. Dual battery setup using a diode based isolator. Old school I know but its worked for over 15 years so why mess with it. The ZAT! Has 2 x 320w panels on the roof. 4 x 6v 370ah batteries. 24v system.
                Attached Files

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                • #9
                  Originally posted by Suprasoup View Post

                  94A7B4CB-DD56-4064-9534-011B8201D600.jpeg7FC21BC0-368A-46B5-AD89-3C4465E2B354.jpeg
                  Indeed!
                  Probably the only times I wish I made my panels tilt able. And Im not removing the snow for solar generation but because Im not a dick and remove snow off my vehicle before I drive on the road.

                  And to the OP. Yup thats my FJ40 towing my Zombie Apocalypse Trailer. ZAT! Both have solar panels on them. The 40 has 2 x 75w panels on the roof rack. Dual battery setup using a diode based isolator. Old school I know but its worked for over 15 years so why mess with it. The ZAT! Has 2 x 320w panels on the roof. 4 x 6v 370ah batteries. 24v system.
                  And I still get asked why I moved to Florida from up North.

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                  • #10
                    Cheers for the differing opinion re: flat mount. I get that they won't be as efficient, but while on the road, why not get something out of them right? And if I happen to park it in the sun in an aussie summer then it's just a bit less hassle setting up camp.

                    I've decided to go with 2x130w to get started. Pop a couple latches and plug in the extension lead and I have a portable 260w with Max 36.6V and 7.1a. Victron mppt 100/20 to look after it; I really doubt I'll need to increase PV but the option is there.Cheers for the differing opinion re: flat mount. I get that they won't be as efficient, but while on the road, why not get something out of them right? And if I happen to park it in the sun in an aussie summer then it's just a bit less hassle setting up camp. Top of the panels will be about 40mm from the roof, methinks - it's a flimsy roof with solid surrounds (pop top), so I'd have to build a bit of a frame anyway.

                    I've decided to go with 2x130w to get started. Pop a couple latches and plug in the extension lead and I have a portable 260w with Max 36.6V and 7.1a. Victron mppt 100/20 to look after it; I really doubt I'll need to increase PV but the option is there.

                    HansWT - regarding the fridge. I've chosen that one b/c it came with the caravan 😁 The 'van is already set up for gas, for cooking and the fridge. TBH I don't mind gas at all. Love it for cooking, I have an outdoor shower setup that can use it for hot showers, and will keep the fridge going for maybe.. $8aud/week. You're right that efficiency is abysmal, 90ltr fridge drawing 12.5a on 12v 😯 I decided to never count on running the fridge off 12v, which has saved a lot in sizing the solar system. I may hook it directly to the car whilst driving. Really I think it'll stay cool enough for that time; I see that option as.. optional atm.

                    I'm interested in your comments on the cooling systems in yours. I don't think the water system is feasible for me as it's a pop top, but I might pull the ceiling apart to throw some insulation up and I hadn't even thought of a thermal wrap. You think that's worthwhile? I do think I'll be adding a 12v extraction fan - atm heat is just building up there with no way out. We don't really spend time inside during the day anyway, unless it's raining. A couple of small fans pointed at the pillows might be a good idea too...

                    Comment


                    • #11
                      Originally posted by SunEagle View Post

                      And I still get asked why I moved to Florida from up North.
                      Obvious! You wanted more humidity, but without it being solid. Sweat instead of sweater.

                      Comment


                      • #12
                        Originally posted by gbynum View Post

                        Obvious! You wanted more humidity, but without it being solid. Sweat instead of sweater.
                        +1

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                        • #13
                          Originally posted by AussieSun View Post

                          I've decided to go with 2x130w to get started. Pop a couple latches and plug in the extension lead and I have a portable 260w with Max 36.6V and 7.1a. Victron mppt 100/20 to look after it; I really doubt I'll need to increase PV but the option is there.


                          I'm interested in your comments on the cooling systems in yours. I don't think the water system is feasible for me as it's a pop top, but I might pull the ceiling apart to throw some insulation up and I hadn't even thought of a thermal wrap. You think that's worthwhile? I do think I'll be adding a 12v extraction fan - atm heat is just building up there with no way out. We don't really spend time inside during the day anyway, unless it's raining. A couple of small fans pointed at the pillows might be a good idea too...
                          Isn't the Victron 100/20 already pushing the limits of your 260 watts??? It's not only what goes into it, but also what comes out. If a 12 volt system... 260/12 is > 21 amps. I was doing similar math with my 20 amp CC when I upgraded to 400 watts, and then I learned 20 amp CC were only good upto around 240 Watts. With 2 panels I was ok. Even with 4 @100 Watts in 2s2p I thought I was good, until I calculated the out... hence going with a 100/40 MPPT.

                          My solar thermal system was "cheap" investment parts wise (< $200 USD), but sweat equity is up there.... lifting my trailer, adding tanks, etc. But overall worth it if I don't need AC. And it will be nicer/more convenient then lugging around a sunshower. But I had previous experience working with solar thermal, so knew the energy capacity/density of water is often higher then battery/PV options alone.... and that heat from the sun was going to go somewhere (most likely places I did not want.

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                          • #14
                            When panels are not aimed properly at the sun, they do not produce their rated power. Additionally, when panels are warm, in the sun, they only produce 80% of name plate power. So in many cases, the full panel nameplate power is never achieved.
                            Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
                            || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
                            || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

                            solar: http://tinyurl.com/LMR-Solar
                            gen: http://tinyurl.com/LMR-Lister

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                            • #15
                              @Mike... a broken clock is right twice a day, solar incident is less so.

                              always better to upsize major components IMHO, as they dictate BoS - balance of system components/sizing, such as wiring.

                              That said, noting your system details... you may be interested in this cheap temperature sensitive relay over a timer on your solar thermal. I wired mine with a on/off/on toggle paralleled through the relay, so I can use my pump for solar 'cooling' with the temp sensor under the roof surface and turn on manually for water supply.

                              Temperature Controller Module... https://www.amazon.com/dp/B07H2X4NNR...p_mob_ap_share

                              I would like to run another off my tanks and dump heat through a small radiator with a much smaller pump, but not gotten that far. I keep my panels/roof below 45C with the relay running on a 3C delta via 2 10 gallon tanks.

                              The power supply is through the leisure light/load on the CC, but it isn
                              Last edited by HansWT; 08-16-2019, 12:59 PM.

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