Page 3 of 3 FirstFirst 123
Results 41 to 57 of 57

Thread: How to select a good 12volt solar panel?

  1. #41
    Premium Member
    ol' boy's Avatar
    Join Date
    Jan 2008
    Posts
    16,510
    Thanks
    7,507
    Thanked 9,140 Times in 4,656 Posts
    Rep Power
    3849
    Reputation
    157872

    Default

    Quote Originally Posted by Thala Dan View Post
    So, I went for one of those flexible panels you have mentioned - have a mate who has had one on top of his Coaster for years, and still going strong.
    Yes, apparently mounting the flexible panel on a bit of coreflute really helps with heat build up
    I know a friend that attached one directly to his caravan roof and it died after the first trip away
    If u want to go on an expedition get a Land Rover, if u want to come home from an expedition get a Landcruiser!



  • #42
    Senior Member

    Join Date
    May 2018
    Posts
    638
    Thanks
    155
    Thanked 672 Times in 305 Posts
    Rep Power
    296
    Reputation
    13014

    Default

    Quote Originally Posted by Thala Dan View Post

    As you probably know, true MPPT regulators aren't all that cheap, and there was a body of opinion that the marginal gains didn't justify the cost.
    Like everything sold by the lying, untrustworthy, and morally bankrupt Chinese, ( sold or manufactured) there are loads of Controllers labeled MPPT which are not.
    Simple ways to get started telling one from the other are a proper MPPT will always have a screen as one needs to do the settings, they will always have a coil inside as needed by the electronic Function of the MPPT circuit and they will cost $50-70 Au as a minimum. Anything cheaper than that is a 99% change it's actually PWM.

    I have been playing with a lot of solar over the last couple of years both Low voltage and gird connect and am also of the belief MPPT is over rated in the low voltage application. In a nut shell it IS more efficient but I believe one has to look at the margins between what one would get with PWM and MPPT. And that is the key, it's the MARGINS between the 2, not the output per se.

    I have a bunch of PWM controllers and the difference in them is Vast. I have one which is brilliant and does a great Job. It has a screen and I can set Multiple Parameters with the thing the most important being cut off voltage. It also has a " Dump" feature where once the battery is charged the load can be diverted to something else so the power is not wasted. I have a couple of others with screens and ajustments as well but they just don't work anywhere as good. The lesser ones I have all interestingly have a USB outlet. I do have a couple I bought as stand by battery chargers for Mowers etc which are also OK. I don't know about the efficency and don't really care. they are on a modified household panel and keep the batteries they are hooked to without cooking them, job done. Bought them a few years ago for around $8 ea as I recall.

    The good ones I looked for a couple of months ago were no longer being sold. Typical. They were Under $20 delivered. I have had one of them on a setup that ran for over a year and never falted.... unlike a number of other components on the same setup that just fell over for no apparent reason.
    A meter I had monitoring the batteries just happened to burst into flames in from of my eyes when I went out to check it one day without touching a thing.
    At least the timing was good if not the quality!

    MPPT is better under non ideal conditions but what you gain in the question. Given the low power one is looking at to start with in a camping situation where you are playing with 100W rather than 5Kw like a house system, To me the margins are going to be too small to worry about.
    I can well see where one might get say 1 Kw with a GOOD PWM ( and there are differences between the same type) and one may get say 1100 Wh with a MPPT.
    The question I'd ask is if that extra 100WH makes a real Difference? I would suggest not.

    It's impossible to put a real world figure on the gains but practicaly I'd be thinking about 10%, Maybe at a big stretch 20% would be about right. I also know that if I was really chasing every watt, re orienting the panel every 30 min would give me a better output with PWM than an MPPT could do ajusted 2-3 times a day.
    It's also going to be rare that someone puts the panel at the correct tilt for that time of the year which would also make more of a difference, small as it may be, to the power generated against an MPPT controller.

    Pulling an extra 10% out of a 5 Kw system over the course of a day at say Sydney latitude on average for the year would be around 2 Kwh. That's a useful amount of energy that could run a TV or a fridge or cover the needs of a Kettle being boiled Multiple times. If we have a 125W folding panel going at name plate generation which will NEVER happen, that same 10% Difference is going to run a camping Fridge for Minutes or a decent LED lighting setup for an hour. For mine it's well and truly far too little energy to be concerned about.

    To break it down into my cost analogy, one would be paying minimum $30 Difference between a decent PWM and MPPT and that $30 will buy a LOT of KW in just Kicking the Vehicle over and letting it run a while. In the case of the 50 Wh gain with an MPPT in the example, It would take seconds Literally to put that extra energy into a battery when you have a potential of 80A and an output of 20+ at Idle.

    Crunching the Numbers ( which I am hopeless at, ) one would expect a 125W panel to produce about 500 Wh in a day. A car alt that put a conservative 20A into a battery would take 15 Min. On my 4L Diesel, that's about 250Ml of fuel or not even .50c worth. Running the vehicle requires only a cable to charge a battery, no extra cost, weight or space.

    Hence the question of the value of spending $150 Plus on a solar panel when you could spend less than even $1 a day on fuel and have a lot more power for anything you wanted.

  • #43
    Senior Member

    Join Date
    May 2018
    Posts
    638
    Thanks
    155
    Thanked 672 Times in 305 Posts
    Rep Power
    296
    Reputation
    13014

    Default

    Quote Originally Posted by oceanboy View Post
    Yes, apparently mounting the flexible panel on a bit of coreflute really helps with heat build up
    Do you meant to help the heat Build-up or Dissipate it?
    Corflute would have insulating properties and make the panel hotter. To keep it cool the best thing would be air Circulation. I don't know anything about these folding panels but if they are waterproof ( and you could get warranty if they proved not to be, lying the things on water would be the best bet IF it were gently moving like on the edge of a creek or wash.

    Reality is though, These things are producing so little power, trying to make them more efficent just like Household panels is really going to be chasing ones tail for very negligeable gains.

  • #44
    Premium Member
    ol' boy's Avatar
    Join Date
    Jan 2008
    Posts
    16,510
    Thanks
    7,507
    Thanked 9,140 Times in 4,656 Posts
    Rep Power
    3849
    Reputation
    157872

    Default

    Quote Originally Posted by george65 View Post
    Do you meant to help the heat Build-up or Dissipate it?
    Corflute would have insulating properties and make the panel hotter.
    Well, dissipate it (yeah poor choice of words)
    I'd have thought Coreflute would allow airflow at the rear of the panel, thus aiding in removing heat soak, when the panel is being fixed to a surface.
    And any breeze would also help move heat soak away

    I know of flex panels that were fixed (glued) direct to metal cladding (caravan roof), that cooked and died.
    Last edited by ol' boy; 19-05-19 at 03:06 PM.
    If u want to go on an expedition get a Land Rover, if u want to come home from an expedition get a Landcruiser!

  • #45
    Senior Member

    Join Date
    May 2018
    Posts
    638
    Thanks
    155
    Thanked 672 Times in 305 Posts
    Rep Power
    296
    Reputation
    13014

    Default

    Corflute ( at least as i know it) is hollow. 2 layers with support inside and hollow space in between. That air gap is insulative. Any time you trap a pocket of air, you impeede the heat transfer from one place to another. This will cause the panel to built heat as there is no cooling air to carry the heat away.

    The same would happen with teh caravan roof. I surmise they are insulated on the back now so there would be little transfer between the aluminium and anything else.
    What is needed for cooling the panels is something to take the heat away. Moving air is good, water is better but something like a sheet of finned aluminium like A heat sink would be better but completely impractical. Again, the gains, other than possibly some longevity I doubt would be worth the trouble.

    I think the bottom lile is these things are completely made as a Commodity to be sold rather than any attention made to quality.
    A rooftop panel is expected to last and the stresses etc are well understood. Something like a camping panel leaves the maker/ seller with a Million excuses to get out of the fact the things are crap quality to start with and even if they have 12 Months warranty, how often are they likely to be used in that time anyway?

    Everything I have seen on these panels says the majority are over rated and crap quality and the decent ones are worth a Bomb.
    With any of them, I can only think people have more money than I do to spend on them.

  • #46
    Senior Member
    Thala Dan's Avatar
    Join Date
    Jul 2012
    Posts
    1,274
    Thanks
    796
    Thanked 1,408 Times in 630 Posts
    Rep Power
    673
    Reputation
    27247

    Default

    The simplest way to determine if a controller is PWM or MPPT is as follows:

    Connect the panel to the controller and thence on to the load

    Connect a voltmeter to the panel input to the controller

    Position the panel so that it's getting direct sunlight and is generating a high-ish voltage, preferably well above the expected output voltage to the load

    When the controller switches on and outputs to the load, observe what happens to the panel voltage on the voltmeter - if it immediately falls to match the load voltage (plus a little bit) then you have a PWM controller.

    If the panel voltage remains reasonable steady at a level above the load voltage or experiences a only small drop, you have a MPPT controller.

    The difference here is that the PWM controller is just a glorified switch that connects and disconnects the panel directly to and from the battery - when connected directly to the battery, the panel voltage is immediately pulled down to match the battery voltage.

    The MPPT controller is essentially an intelligent DC-DC converter - it takes the input voltage from the panel and converts it internally to an appropriate voltage for the battery, without affecting the panel input voltage, other than normal power loading effects.

  • #47
    Senior Member
    Thala Dan's Avatar
    Join Date
    Jul 2012
    Posts
    1,274
    Thanks
    796
    Thanked 1,408 Times in 630 Posts
    Rep Power
    673
    Reputation
    27247

    Default

    Quote Originally Posted by oceanboy View Post
    Another option for a foldable 120W panel
    (I'd say this is better than what i purchased, as everything has proper 50Amp Anderson Plugs and cabling looks heavier and the Solar Controller is much better.

    OB,

    I've got one of those blue controllers shown in the Sunyee listing - have played with it but never installed anywhere 'cause it's pretty ordinary construction.

    One word of warning though - I read the feedback on some eBay sellers listing of this controller (they've all got the damn things) and one bloke reckons he nearly lost his caravan because of it - apparently just by chance was nearby when the damn thing started cooking his battery.

    Can't vouch for it one way or t'other, but worth keeping in mind.

  • The Following User Says Thank You to Thala Dan For This Useful Post:

    ol' boy (19-05-19)

  • #48
    Premium Member
    ol' boy's Avatar
    Join Date
    Jan 2008
    Posts
    16,510
    Thanks
    7,507
    Thanked 9,140 Times in 4,656 Posts
    Rep Power
    3849
    Reputation
    157872

    Default

    Quote Originally Posted by george65 View Post
    With any of them, I can only think people have more money than I do to spend on them.
    That can be a valid point, in my 30 years of camping and 15 years of having a 12volt compressor fridge
    (Had a 3-Way fridge prior that)
    I can only think of 3 occasions i really needed Solar to keep my 100Ah battery from discharging beyond 50% SoC.

    For the $300 i just spent for 2 foldable panels, that would be a lot of diesel or petrol to run the vehicle and use the Alternator.
    But, we have to move on... The technology is there and Solar is silent.

    I could by-pass the lot by just going back to a thick Esky that holds ice for 4 days (No battery needed, No Charger, No wiring, No Solar Panels)
    Last edited by ol' boy; 19-05-19 at 04:35 PM.
    If u want to go on an expedition get a Land Rover, if u want to come home from an expedition get a Landcruiser!

  • #49
    Premium Member
    ol' boy's Avatar
    Join Date
    Jan 2008
    Posts
    16,510
    Thanks
    7,507
    Thanked 9,140 Times in 4,656 Posts
    Rep Power
    3849
    Reputation
    157872

    Default

    Quote Originally Posted by Thala Dan View Post
    OB,

    I've got one of those blue controllers shown in the Sunyee listing - have played with it but never installed anywhere 'cause it's pretty ordinary construction.

    One word of warning though - I read the feedback on some eBay sellers listing of this controller (they've all got the damn things) and one bloke reckons he nearly lost his caravan because of it - apparently just by chance was nearby when the damn thing started cooking his battery.

    Can't vouch for it one way or t'other, but worth keeping in mind.
    Cheers, yes that is a worry
    To be honest, i am only after the best panel option/type, i have MPPT and Multi Stage charging handled by the DC-DC charger



    To add, i know the Victron Blue MPPT Solar Controllers also get very warm when operating



    If i was going to use the supplied PWM controller on a regular basis, i'd probably buy a better one i think.
    Last edited by ol' boy; 19-05-19 at 04:40 PM.
    If u want to go on an expedition get a Land Rover, if u want to come home from an expedition get a Landcruiser!

  • #50
    Premium Member
    ol' boy's Avatar
    Join Date
    Jan 2008
    Posts
    16,510
    Thanks
    7,507
    Thanked 9,140 Times in 4,656 Posts
    Rep Power
    3849
    Reputation
    157872

    Default

    Quote Originally Posted by george65 View Post

    I bought a stack of 190W used house panels this morning for $11 ea.
    What output voltage are they george?
    The Victron MPPT has a rather high input voltage for a 12v solar controller...





    Would a house panel work with this controller you think?
    Last edited by ol' boy; 20-05-19 at 06:33 PM.
    If u want to go on an expedition get a Land Rover, if u want to come home from an expedition get a Landcruiser!

  • #51
    Senior Member

    Join Date
    May 2018
    Posts
    638
    Thanks
    155
    Thanked 672 Times in 305 Posts
    Rep Power
    296
    Reputation
    13014

    Default

    Hard to say. The panels I got are the same as others I have used on the controller I have. The 190s are 36.6 working but pull down under load. The 180's
    used on my controller were 37V and they worked no problem.

    all the controller s I have seen work in a range much higer than the rating. The one I have is 19V I think it is input to work with a 12V battery and 38 I think to work with a 24V setup. You would need to look up the actual specs of the controller to see the max input voltages.

    I set up a solar/ Led skylight in the kitchen. Rather than cut aq hole in the roof and spend a grand, I threw up 2 panels in series and got a voltage reducer that woks from I think 45V and takes it down to 24. This was within the rating of the LED lamps I use and they run happily from it all day giving more light than what a skylight would early, late and on cloudy days because the panels are so over rated for the Load of the LED's.
    I can't remember what the rating of the converter was now but I bought the Biggest and from memory it was $16. I have a feeling it was 300W.
    You could hook the panels to the voltage regulator and then to the Controller.
    Obviously going to loose some efficiency but for the price.....


    There is another trick I figured out and have used but only ever once seen mentioned to get the voltage of a panel down.
    On the back of the panel there will be a box where the leads come out. If you pry that open you will see 3 Diodes. The panels are wired in 3 sections and wired in series. The 190W panels are 46V open circuit so you get more than 12V per .... set.. of cells. If you tap off each diode like 3 phase, 1-2, 2-3, 3-1, you get higher current but lower voltage. I did this with a panel to get 24V tolerable output from a panel. Left me with a spare/ wasted section but that was not a concern for the job at hand. I used 2 panels so paralleled the 2 spare sections I had to come up with 3 inputs and make full use of the panels total output and still get the 24+V I needed.

    To split the panel you want to use 72 cell panels rather than 60's ( 36V working rather than 30) to get the voltage above 12 V for battery charging. As one is sailing close to the wind on this anyway, a PROPER MPPT charger would be preferential because they have a buck and boost capability where as a PWM can only charge 12v from 15v + or so input. Splitting a 72 Cell panel will give you 15V per " Phase" which will drop under load even in parallel unless the load is very light.

    A PWM would generally not be able to charge a battery from a 12V Input no matter what the amps but within a fair range, an Mppt don't care so much. It will take the amps at 10V or lower and multiply that to Volts it needs to charge the battery to the end/ float charge level as you program in.

    Doing the homework for you, ( My god there is some shit being passed off on fleabay as MPPT when it's PWM and crap PWM at that!)This is still the cheapest true MPPT Controller out there:



    The problem may be they only do down to -24V- NOT 12.

    The more exy ones may be OK with 12 but anything cheaper than this is NOT MPPT wether it says so or is advertised as being so or not.
    I see an orange and blue large controller for about the same price being MPPT but sadly that are a crock as well.


    This:

    Appears to be the cheapest MPPT that will do a 12V battery. If you were going to split a 36V/ 72 cell panel, this would be the place to start. I notice you can add accessories to these to like remote meters. Not sure if you would want that for camping but these things seem to be built for more permanant use so should be robust.

  • #52
    Premium Member
    ol' boy's Avatar
    Join Date
    Jan 2008
    Posts
    16,510
    Thanks
    7,507
    Thanked 9,140 Times in 4,656 Posts
    Rep Power
    3849
    Reputation
    157872

    Default

    Yeah, I've seen those MPPT controllers on eBay... Some are just a big empty box!
    They seem the popular model now

    There was a MPPT that everyone used years ago, still a sort after unit now... For 12v work.
    It's around $74.50 so a similar price

    The next good one is this, with Low Temp cut off and full logging



    But i'd buy the Victron if i was going down the separate solar controller/charger path
    (firmware upgradable, good warranty, customer service and plenty of them out there running very happily)
    Last edited by ol' boy; 21-05-19 at 06:15 PM.
    If u want to go on an expedition get a Land Rover, if u want to come home from an expedition get a Landcruiser!

  • #53
    Senior Member
    Uncle Fester's Avatar
    Join Date
    Jan 2008
    Location
    Commonly found in a pantry or the bottom of a fridge, searching for grains, fermented or distilled
    Posts
    4,646
    Thanks
    1,401
    Thanked 2,701 Times in 1,601 Posts
    Rep Power
    1246
    Reputation
    47518

    Default

    I have that Victron controller on my other site. It is very compact.
    You can use 24V house panels (in series up to 100V) and charge a 12V battery with it. It detects the battery voltage and switches automatically to the right voltage.

    I have an inverter from EPEVER here at home and it is the only Chinese inverter I have used that has performed perfectly for over a year in daily (actually nightly) use now and costs a fraction of the smaller Victron Inverter in the other site. I would expect their controller to work equally well.

    BTW this is the highly customisable controller I am using in my 48V power bricks, it is rated for 50A and is cheaper than the 10A version of the EPEVER and has performed also flawlessly, nevertheless I keep a spare, because it is so cheap for what it can do:


    LOL, I just saw on that link that the Chinese are warning of fakes of their own products.
    Last edited by Uncle Fester; 21-05-19 at 11:30 PM.
    This era of thoughtless consumption must end so we can encourage a world of creative geniuses rather than consumer idiots.


  • The Following User Says Thank You to Uncle Fester For This Useful Post:

    ol' boy (22-05-19)

  • #54
    Premium Member
    ol' boy's Avatar
    Join Date
    Jan 2008
    Posts
    16,510
    Thanks
    7,507
    Thanked 9,140 Times in 4,656 Posts
    Rep Power
    3849
    Reputation
    157872

    Default

    Thanks nomeat.
    I saw those (makeskyblue) on eBay here also.
    Appreciate the heads up on the Victron
    If u want to go on an expedition get a Land Rover, if u want to come home from an expedition get a Landcruiser!

  • #55
    Premium Member
    ol' boy's Avatar
    Join Date
    Jan 2008
    Posts
    16,510
    Thanks
    7,507
    Thanked 9,140 Times in 4,656 Posts
    Rep Power
    3849
    Reputation
    157872

    Default

    Anyone interested in the Champion 125Watt foldable blanket, they are even cheaper now $149 down to $75!
    At Bunnings, but you'll have to ring to find stock

    Was in Supercheap this week, they have the same thing for $430

    Last edited by ol' boy; 22-06-19 at 11:12 AM.
    If u want to go on an expedition get a Land Rover, if u want to come home from an expedition get a Landcruiser!

  • #56
    Senior Member

    Join Date
    May 2018
    Posts
    638
    Thanks
    155
    Thanked 672 Times in 305 Posts
    Rep Power
    296
    Reputation
    13014

    Default

    Quote Originally Posted by oceanboy View Post
    Anyone interested in the Champion 125Watt foldable blanket, they are even cheaper now $149 down to $75!
    I just Bought 6 KW of 250W Panels for $15 ea.
    Yes, they were non folding and used but I'm not complaining.

  • #57
    Senior Member
    eeprommemory's Avatar
    Join Date
    Jan 2008
    Location
    ADL
    Posts
    950
    Thanks
    753
    Thanked 399 Times in 200 Posts
    Rep Power
    282
    Reputation
    5491

    Default

    Quote Originally Posted by george65 View Post
    Hard to say. The panels I got are the same as others I have used on the controller I have. The 190s are 36.6 working but pull down under load. The 180's
    used on my controller were 37V and they worked no problem.

    all the controller s I have seen work in a range much higer than the rating. The one I have is 19V I think it is input to work with a 12V battery and 38 I think to work with a 24V setup. You would need to look up the actual specs of the controller to see the max input voltages.

    I set up a solar/ Led skylight in the kitchen. Rather than cut aq hole in the roof and spend a grand, I threw up 2 panels in series and got a voltage reducer that woks from I think 45V and takes it down to 24. This was within the rating of the LED lamps I use and they run happily from it all day giving more light than what a skylight would early, late and on cloudy days because the panels are so over rated for the Load of the LED's.
    I can't remember what the rating of the converter was now but I bought the Biggest and from memory it was $16. I have a feeling it was 300W.
    You could hook the panels to the voltage regulator and then to the Controller.
    Obviously going to loose some efficiency but for the price.....


    There is another trick I figured out and have used but only ever once seen mentioned to get the voltage of a panel down.
    On the back of the panel there will be a box where the leads come out. If you pry that open you will see 3 Diodes. The panels are wired in 3 sections and wired in series. The 190W panels are 46V open circuit so you get more than 12V per .... set.. of cells. If you tap off each diode like 3 phase, 1-2, 2-3, 3-1, you get higher current but lower voltage. I did this with a panel to get 24V tolerable output from a panel. Left me with a spare/ wasted section but that was not a concern for the job at hand. I used 2 panels so paralleled the 2 spare sections I had to come up with 3 inputs and make full use of the panels total output and still get the 24+V I needed.

    To split the panel you want to use 72 cell panels rather than 60's ( 36V working rather than 30) to get the voltage above 12 V for battery charging. As one is sailing close to the wind on this anyway, a PROPER MPPT charger would be preferential because they have a buck and boost capability where as a PWM can only charge 12v from 15v + or so input. Splitting a 72 Cell panel will give you 15V per " Phase" which will drop under load even in parallel unless the load is very light.

    A PWM would generally not be able to charge a battery from a 12V Input no matter what the amps but within a fair range, an Mppt don't care so much. It will take the amps at 10V or lower and multiply that to Volts it needs to charge the battery to the end/ float charge level as you program in.

    Doing the homework for you, ( My god there is some shit being passed off on fleabay as MPPT when it's PWM and crap PWM at that!)This is still the cheapest true MPPT Controller out there:



    The problem may be they only do down to -24V- NOT 12.

    The more exy ones may be OK with 12 but anything cheaper than this is NOT MPPT wether it says so or is advertised as being so or not.
    I see an orange and blue large controller for about the same price being MPPT but sadly that are a crock as well.


    This:

    Appears to be the cheapest MPPT that will do a 12V battery. If you were going to split a 36V/ 72 cell panel, this would be the place to start. I notice you can add accessories to these to like remote meters. Not sure if you would want that for camping but these things seem to be built for more permanant use so should be robust.
    i have both of those controllers the mpt-7210A works from 10V to 50V nothing else on the market works as good as it does.
    you can set the voltage to exactly what you want and you can set the charge current to exactly what you want.
    i hooked it up to a variable power supply set the input voltage to 10V and set the battery charge voltage to 14.40V and it charged at 4amps (i set that) then as the battery charged the current dropped after it got to 14.40V.
    its all on the display no screwing around with multi-meters.
    i purchased a few solar controllers and most that said they were MPPT had no toroid inside and were PWM junk.
    Last edited by eeprommemory; 08-08-19 at 05:50 PM. Reason: typo

  • Page 3 of 3 FirstFirst 123

    Bookmarks

    Posting Permissions

    • You may not post new threads
    • You may not post replies
    • You may not post attachments
    • You may not edit your posts
    •