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150W monocrystalline with PWM vs 200W polycrystalline with MPPT

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  • 150W monocrystalline with PWM vs 200W polycrystalline with MPPT

    I am completely new to solar power and I am considering buying a solar panel system for an off-grid hut in Wales, where I will be staying during the month of February. I require roughly 100 to 200 daily Watt-hours to power an LED light and a laptop on which I will be working. I have found two solar panels on ebay that seem to fit my needs, but as I have zero experience in buying solar panels, I thought I'd ask here before going ahead with the purchase.

    Here are the two panels:
    http://www.ebay.co.uk/itm/150W-solar...item463066bf9f
    http://www.ebay.co.uk/itm/2-100Watt-...3D301459750815

    My main question is: Would it be better to buy the 150W monocrystalline panel with its included PWM charge controller, or the 200W polycrystalline panel with its MPPT charge controller? (Both controllers are rated at 20Ah). I know that monocrystalline panels are slightly more efficient, but I assume the extra 50W of panel would counter this. I've also heard that MPPT charge controllers are more efficient in systems of 150W and higher, and also in cold conditions (I will be using the panel in British winter at a reasonably high altitude). Taking this into consideration, which panel would be more suitable?

    Any help would be much appreciated.

    Antony

  • #2
    The 150 watt panel with PWM at best will supply 8 amps. The 200 watt panel with MPPT at best will supply 17 amps or more than twice the power on the output.
    MSEE, PE

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    • #3
      i have the ecoworthy 20amp mppt controller that is showned with the 200 watt kit, so i can ascertain that it is reliable and a true mppt, i been using mine 24/7 for almost 2 years.
      And i have to agree 200 watts is better than 150 watts, 2 or 3 extra amps dont sound like alot but in the solar world it is. It gets your battery charged quicker which is always good.

      on my 240 watt panel with the ecoworthy mppt at most i average about 12 amps at midday but my panel is lying flat on my roof , the most I seen is 15 amps but only for a few seconds, but usually by noon the battery is already in float mode. So with 200 watts you probably get something like that or lower unless you point it at the sun. For my needs running my laptop, swamp cooler, charging my power tools, using my roadpro cooker, all my fluorescent lights its more than enough.

      I think 200 watts will easily handle your needs as long as the sun is good to you.

      The only thing with the ecoworthy mppt controller is that it goes from bulk, maybe spend 2 or 3 minutes in absorption then go straiqht to float. Its either in bulk or float, this has been mentioned in other forums. There is no setting for how long to keep the battery in absorption as in other high end mppt controllers. Even though it never goes to absorption it does keep my battery charged up and its the only thing thats charge the battery in 2 years. It never overcharges the battery, If the battery is full, and the sun is overhead I seen it floating at less than 1 amp.

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      • #4
        Great, many thanks to both of you. I'm glad to hear that the charge controller on the 200W panel is reliable and well-known. So all-in-all, the 200W MPPT deal is a better one, even though it's polycrystalline. I'm guessing that even if the 150W panel had the same MPPT controller, the output (despite being monocrystalline) would still be much lower than the 200W panel?

        In terms of matching a battery to this panel, would the following be okay (ie. enough Ah to ensure I'm not wasting any power and to ensure it doesn't go below 50% charge)? I had a quick check on some battery sizing calculators and it seemed to be fine, but as it's from ebay, I thought I'd double-check here to ensure the brand etc are all okay as well:
        http://www.ebay.co.uk/itm/100Ah-12V-...item1e7f26c0df

        I've also found this inverter (it needs to be pure sine wave as I'm using a laptop and sound equipment with it).
        http://www.tlc-direct.co.uk/Products...FYKWtAod_HEA3A
        Has anyone used one of these, or if not, are you able to tell if it will be adequate?

        Apologies for all the follow-up questions, I just want to be sure before I buy. I can go ahead and ask these questions on a separate thread if needs be.

        Comment


        • #5
          I suspect that polycrystalline is not only ok for you but better. Polycrystalline will still give you their rated power, they're just a little bigger than more efficient technology. So it you were covering that hut in panels trying to get the most power you could then sure efficiency would matter but to you it's just throwing money away to make your panels slightly smaller.

          Originally posted by antobag View Post
          In terms of matching a battery to this panel, would the following be okay (ie. enough Ah to ensure I'm not wasting any power and to ensure it doesn't go below 50% charge)? I had a quick check on some battery sizing calculators and it seemed to be fine, but as it's from ebay, I thought I'd double-check here to ensure the brand etc are all okay as well:
          http://www.ebay.co.uk/itm/100Ah-12V-...item1e7f26c0df
          Does Wales get sun in February?

          Originally posted by antobag View Post
          I've also found this inverter (it needs to be pure sine wave as I'm using a laptop and sound equipment with it).
          http://www.tlc-direct.co.uk/Products...FYKWtAod_HEA3A
          Has anyone used one of these, or if not, are you able to tell if it will be adequate?
          I would think overkill. Laptops and light bulbs don't need pure sine wave, you could go much cheaper. Which would also be better for you as those pure sine wave inverters use much more power than their modified square wave equivalents.

          Comment


          • #6
            Originally posted by Bucho View Post
            I suspect that polycrystalline is not only ok for you but better. Polycrystalline will still give you their rated power, they're just a little bigger than more efficient technology. So it you were covering that hut in panels trying to get the most power you could then sure efficiency would matter but to you it's just throwing money away to make your panels slightly smaller.
            Perfect, thanks for the clarification.

            Originally posted by Bucho View Post
            Does Wales get sun in February?
            Haha yes, albeit rare! I've estimated that I'll get slightly less than an hour's worth of usable sunshine daily, so the 200W solar panels should provide about 170W per day. Also, I've heard that in order to make the full use of MPPT charge controllers, the array voltage should be substantially higher than the battery voltage. Would the 100Ah battery be okay for this?

            Originally posted by Bucho View Post
            Laptops and light bulbs don't need pure sine wave, you could go much cheaper. Which would also be better for you as those pure sine wave inverters use much more power than their modified square wave equivalents.
            The main reason I was going for pure sine wave was because I heard that modified square wave inverters can make a slight buzzing sound when using audio equipment (I'll be recording audio with microphones, electric guitar, etc). BUT I've just realised that nearly all of my audio equipment runs through an interface that is powered by the usb port in my laptop, so it is never directly powered by the mains. Would it still be affected by the buzzing?

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            • #7
              Originally posted by antobag View Post
              Haha yes, albeit rare! I've estimated that I'll get slightly less than an hour's worth of usable sunshine daily, so the 200W solar panels should provide about 170W per day.
              That's a very short period of sun and I recall spending a week in England where I never did see the sun. What I'm trying to get at is if you need to have dependable power well you'll realistically need a generator and since you need the generator anyway....

              If you only need this for February I wonder what a month of gas would cost you?

              Originally posted by antobag View Post
              Also, I've heard that in order to make the full use of MPPT charge controllers, the array voltage should be substantially higher than the battery voltage. Would the 100Ah battery be okay for this?
              I'm not familiar with your battery but if you're talking about wiring your panels in series I don't think that gets you anything battery-wise. The thing you would get with higher voltage is less power lost due to voltage drop, so how far between your panels and charge controller?

              Originally posted by antobag View Post
              The main reason I was going for pure sine wave was because I heard that modified square wave inverters can make a slight buzzing sound when using audio equipment (I'll be recording audio with microphones, electric guitar, etc). BUT I've just realised that nearly all of my audio equipment runs through an interface that is powered by the usb port in my laptop, so it is never directly powered by the mains. Would it still be affected by the buzzing?
              Well I don't know a thing about audio equipment but the inverter idles at .6 amps so at 12 volts that's 7.2 watts which over 24 hours is 172.8 Wh. So without even doing anything you could spend more power than your bringing in if you leave the inverter on.

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              • #8
                Originally posted by antobag View Post
                The main reason I was going for pure sine wave was because I heard that modified square wave inverters can make a slight buzzing sound when using audio equipment (I'll be recording audio with microphones, electric guitar, etc). BUT I've just realised that nearly all of my audio equipment runs through an interface that is powered by the usb port in my laptop, so it is never directly powered by the mains. Would it still be affected by the buzzing?
                In addition to feeding through inadequate filters in the DC power supplies, the MSW will radiate interference from the AC lines and from the inverter itself. That will affect audio if you use unshielded cables or run them too close to your AC wiring, and it can affect radio and TV reception in particularly bad cases.
                SunnyBoy 3000 US, 18 BP Solar 175B panels.

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                • #9
                  Originally posted by inetdog View Post
                  In addition to feeding through inadequate filters in the DC power supplies, the MSW will radiate interference from the AC lines and from the inverter itself. That will affect audio if you use unshielded cables or run them too close to your AC wiring, and it can affect radio and TV reception in particularly bad cases.
                  If using a Modified sine wave inverter, you will/may be using a lot more power for powering an device than if you would be using a full sine wave inverter.

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                  • #10
                    I can also vouch for the Eco-worthy 20 amp MPPT controller. I got my forst one shortly after they came out and have been happy since.

                    On Poly vs mono panels. Set one of each with matching wattage out in the sun. Their numbers will be similar until the lightest of cloud covers come in. When that happens the Poly drops its output depending on how thick the cloud cover is. The Mono's take a swan dive as soon as any cloud cover exist. My Bosch 245w mono will drop to 2.38a with any cover, My 230w Schott poly will put out 4a in pea soup thick enough that I'm really only pointing the panel at the brightest point in the clouds. The mono system is asleep at that point. Those four amps kept us off the generator by stretch our battery on a cloudy day sandwiched between two freezing nights.

                    Comment


                    • #11
                      Many thanks for all of your replies. I've tried to respond to all of them:

                      Originally posted by Bucho
                      If you only need this for February I wonder what a month of gas would cost you?
                      We also hope to use the solar panels later on our house (my dad and I are really interested in off-grid living and we've always wanted to buy solar panels), so my off-grid stint in Wales in February is a sort of "testing period" for later. I did consider only using a generator but I'd love to be able to rely on solar as much as possible. I guess one of my main reasons for doing it are for the challenge and the satisfaction of setting it all up.

                      Originally posted by Bucho
                      The thing you would get with higher voltage is less power lost due to voltage drop, so how far between your panels and charge controller?
                      I'm pretty sure the charge controller will be right next to the panels, so I guess I don't need to worry about this.

                      Originally posted by Bucho
                      Well I don't know a thing about audio equipment but the inverter idles at .6 amps so at 12 volts that's 7.2 watts which over 24 hours is 172.8 Wh. So without even doing anything you could spend more power than your bringing in if you leave the inverter on.
                      That comes at quite a shock, I didn't realise the inverter would use so much power. In order to charge my laptop, I really do need to be using AC power (it's the only way I can plug my laptop in) - I assume I should use modified square wave in order to prevent the inverter from leeching all of my power?

                      Originally posted by inetdog
                      In addition to feeding through inadequate filters in the DC power supplies, the MSW will radiate interference from the AC lines and from the inverter itself. That will affect audio if you use unshielded cables or run them too close to your AC wiring, and it can affect radio and TV reception in particularly bad cases.
                      I am now thinking that any time I am making an audio recording, I could run the laptop on its own battery power. This should avoid any interference with the audio. When mixing/editing/etc, I guess I will just have to make do with hearing interference over my headphones.

                      Originally posted by Johann
                      If using a Modified sine wave inverter, you will/may be using a lot more power for powering an device than if you would be using a full sine wave inverter.
                      Sorry, I'm a bit confused here. Are you saying that the modified sine wave inverter will provide me with more power, or that it will use up more power? Apologies if I'm being a bit slow, this is all very new to me.

                      Originally posted by jimindenver
                      I can also vouch for the Eco-worthy 20 amp MPPT controller. I got my forst one shortly after they came out and have been happy since.

                      On Poly vs mono panels. Set one of each with matching wattage out in the sun. Their numbers will be similar until the lightest of cloud covers come in. When that happens the Poly drops its output depending on how thick the cloud cover is. The Mono's take a swan dive as soon as any cloud cover exist. My Bosch 245w mono will drop to 2.38a with any cover, My 230w Schott poly will put out 4a in pea soup thick enough that I'm really only pointing the panel at the brightest point in the clouds. The mono system is asleep at that point. Those four amps kept us off the generator by stretch our battery on a cloudy day sandwiched between two freezing nights.
                      Thanks jimindenver, it's really helpful to hear some personal experiences. It seems that the MPPT controller with the poly panels would be the best choice for me then.

                      Comment


                      • #12
                        ''''Sorry, I'm a bit confused here. Are you saying that the modified sine wave inverter will provide me with more power, or that it will use up more power? Apologies if I'm being a bit slow, this is all very new to me.''''

                        The modified sine wave inverter will need more power or take more power from your battery bank to give your device the necessary wattage that it needs to operate. A full sine wave inverter may need less power from your battery bank to do the same amount of work. Here is a youtube clip that may show you this better. www.youtube.com/watch?v=wimTJw_Gpgk&list=UUVktNhxFTBnrLfeIe1tdgSQ

                        Comment


                        • #13
                          Okay, so it seems there are two different lines of thought regarding the power usage of inverters in this thread:

                          Originally posted by Johann View Post
                          The modified sine wave inverter will need more power or take more power from your battery bank to give your device the necessary wattage that it needs to operate. A full sine wave inverter may need less power from your battery bank to do the same amount of work.
                          Originally posted by Bucho View Post
                          those pure sine wave inverters use much more power than their modified square wave equivalents.
                          I'm guessing it all boils down to how I'll be using the inverter. Considering that I'll be powering a standard laptop (runs at a rate of about 30-40W) and an LED light (4W), is it possible to estimate which type of inverter would result in the lowest consumption of power? Does the inverter's wattage rating affect the amount of power it consumes (ie. should I go for the lowest wattage possible for my needs)?

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                          • #14
                            There are other advantages to using PSW over MSW. Your computer uses a brick to charge with, that brick will be much cooler in use with PSW. The microwave will run better and motors will start easier.

                            Going PSW on the small side doesn't have to cost a arm and a leg. It's the big PSW inverters that can break the bank. There are cheapies but you have to get one the size of a bus to run a 500w load. They have high idle draws and break it and it is disposable as the warranty isn't worth the paper it's written on.

                            I use a Powerbright MSW 150w inverter for my TV, satellite and phone charger and while nothing has died, the charger and satellite box sure do get warmer than normal. I'll upgrade to a Morningstar 300w PSW that is fan less. Not having to listen to the fan will be worth the upgrade in its self.

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                            • #15
                              I'll quote myself about inverters:

                              Pure sine vs Mod sine inverters. Pure sine are less efficient at the 12V end, because of losses creating a nice sine wave. All gear works great on pure sine.

                              Mod sine is a bit more efficient on the 12V end because it's a much simpler circuit, BUT powering loads with mod sine can cause problems with some (portable tool rechargers are sometimes very picky about their power) devices, problems with motors - motors buzz, get hotter from the harmonics and draw MORE power when on mod sine. Small device wall wart power supplies can overheat on mod sine, and you have to replace them, or put the smoke back inside the parts.

                              Incandescent lights, and heating appliances are about the only thing that don't care about mod OR pure power.
                              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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