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Thread: How does $2/watt sound?

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    Default How does $2/watt sound?

    Just wondering if this is a good deal?

    I know prices will drop, BUT... I want a panel on the work truck to keep the inverter battery topped up....

    Reality is an invention of my imagination.
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    cost last time I checked was hovering around $1.40/watt FOB China so the price seems pretty fair

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    $2 per watt for a 50 watt panel is good. I just paid $1.40 per watt for a 200 watt panel. Prices sure are coming down.

    What sort of battery is the inverter battery? Are you going to use a charge regulator?

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    200ah agm
    Reality is an invention of my imagination.
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    Quote Originally Posted by Learjet View Post
    $2 per watt for a 50 watt panel is good. I just paid $1.40 per watt for a 200 watt panel. Prices sure are coming down.
    Got a link?
    Reality is an invention of my imagination.
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    Marsol are selling them on ebay.

    Or you can get them from their website.

    There's a piccy of it in my thread.
    Last edited by Learjet; 26-01-12 at 01:33 PM.

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    Quote Originally Posted by Learjet View Post
    Marsol are selling them on ebay.

    Or you can get them from their website.

    There's a piccy of it in my thread.
    Those panels look good.

    To save some people getting ripped off I would like to warn people about another Ebay seller called LHP-net-au AKA , Leisure Home Products, .net.au/ &
    energystore.com.au/

    Be warned.

    My experience with him was buying 2 x120 w solar panels that were actually 80 w panels with a 120w very dodgy label & a 45A regulator (he sent a 20A Reg) when confronted with a paypal dispute & a report to the police for fraud he sent another of the dodgy panels to make up the wattage shortfall & the correct 45A Reg. After I returned the 20A Reg.
    It wasn't a pleasant experience.
    Cheers, Tiny
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    Yes I bought my first panel from LHP. They are not up to spec. Their 50 watt is more like 25 watt, though I got it so cheap at the time I guess I got what I paid for.

    These days when buying (moncrystalline) panels I take careful note of the physical size, generally since efficiency per size of cheap mono panels from China is roughly similar. LHP panels are physically smaller than most others at similar rating, which means they are lying about the rating. An amp meter soon confirmed that.

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    The worst part was the gear was for a neighbor, so I ended up taking the panels & buying the neighbor the real deal.

    The first thing that twigged my suspicion was physical size, then side by side comparison with a known panel & 2 Amp meters proved the point.

    This happened over a year ago, just thought I'd warn everyone.
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    I just bought a 200W panel to power my pool chlorinator from Marsol and they are not up to spec either.

    140W is more realistic.

    Problem is they are spec'ed @ 11Amps but for 200W you would need to get a maximum power point voltage (MPPV) of 18.2V!
    This might be possible in outer space .

    Open circuit voltage(OCV) is 19V when the panel gets hot under full sun.
    The standard (on this planet) is MPPV = OCV x 0.76 (14.44V)

    My tests using variable resistive loads revealed an actual MPPV with this panel of 14.5V @ 9.5Amps.
    (138W)
    I have an older 120W panel delivering over 105W under the same conditions so I should be getting at least 175W.
    This era of thoughtless consumption must end so we can encourage a world of creative geniuses rather than consumer idiots.


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    Quote Originally Posted by Learjet View Post
    Marsol are selling them on ebay.

    Or you can get them from their website.

    There's a piccy of it in my thread.
    Have you done measurements with your 200W panel that confirm it's specs?

    What kind of regulator are you using?

    I also tried an MPPT regulator from Ebay type WELLSEE WS-MPPT15 and it is total garbage. There is 10% loss rather than the advertised 10-30% gain and at a battery terminal voltage over just 12.0V it switches to a pulsating slow charge of 2 A average (checked with a scope) and of course none of the valuable power from the panel is passed onto the load.
    I complained to the factory and they told me I should not worry, that's how it works,

    Luckily I am tracking the battery voltage with my chlorinator design so I just used a spare port from the PIC to switch a simple relay to directly connect the panel to the battery and of course also disconnect when it is dark...and binned the regulator. Cost too much to send back and I can use the MOSFETS and maybe the PIC inside.

    I'll try to deal 50% refund, they usually do that if they send crap.
    This era of thoughtless consumption must end so we can encourage a world of creative geniuses rather than consumer idiots.


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    Quote Originally Posted by nomeat View Post
    Have you done measurements with your 200W panel that confirm it's specs?

    What kind of regulator are you using?
    I just did a quick and dirty test on my 200 watt nomeat as it was cloudy the day I connected it. The quick and dirty involved comparing it to 2x50 watt panels in parallel under a dead short. Under that test it gave about twice the amps.

    If it's sunny tomorrow I'll connect the 200 watt alone and see how many amps it's pushing, but there's going to be some loss in the wiring to it. I used what I had on hand which is 4mm square so there's going to be some resistance in that. Plus another 7 metres of 8 AWG running to the controller. I've been upgrading the wire as funds permit. If I don't get my daily headache I might see if I can measure at the panel if it's sunny.

    My controller is a PWM Manson SBC-7130.

    Jacar sell them rebadged.

    I've been wondering about those wellsee MPPT regulators. But the very name put me off.

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    mppt's seem to be ok for small setups , like electric fences or small pump systems

    on the house system here i use a plasmatronics PL60 on the main circuit, its a PWM regulator, but it applies full power from the panels right up until it thinks the batteries are just about charged then it switches to a pulse width modulator to float the battery bank and spike in some more storage.

    also a 40 amp yellow box on the 12 volt circuit, it was supplied years ago from windpower australia. one of Clives products. its a on-off reg.
    cheers from the bush
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    Quote Originally Posted by Learjet View Post
    I just did a quick and dirty test on my 200 watt nomeat as it was cloudy the day I connected it. The quick and dirty involved comparing it to 2x50 watt panels in parallel under a dead short. Under that test it gave about twice the amps.

    If it's sunny tomorrow I'll connect the 200 watt alone and see how many amps it's pushing, but there's going to be some loss in the wiring to it. I used what I had on hand which is 4mm square so there's going to be some resistance in that. Plus another 7 metres of 8 AWG running to the controller
    My panel did well under clouds too. In fact the difference between a slightly hazy and a deep blue sky is perhaps 10W.

    If you open the little black box (wedge a small screw driver in the small opening between the cables) and you find that the panel is split in three groups with three reverse current protection diodes in series, chances are we have the same type of panel. Try to measure the voltage under full load directly on the outer terminals in the box, while you measure the current.
    It is the only way to get an accurate reading of the wattage and you can also find out how much loss on the cables you really have.

    I would be grateful to know your results as this might help me dealing with Marsol.
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    When I first got the panel I looked in the junction box and saw 3 diodes so it may be the same.

    I don't have a variable resistive load, nor a fixed load that will take 10+ amps that I can think of. Any ideas? The panel is now bolted in it's final position so I can't remove it. And I can't get a 40kg battery to it either.

    I can test for dead short at the panel, or charge rate through lossy cable.

    Edit, I could use a length of cable for a resistive load, although it's not likely to be at MPP.
    Last edited by Learjet; 19-02-12 at 03:52 AM.

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    Quote Originally Posted by Learjet View Post
    Edit, I could use a length of cable for a resistive load, although it's not likely to be at MPP.
    Yes that would work.

    I reached MPP between 1.5 and 1.6 Ohm, it is not extremely critical, but I need to know the exact value.

    Perhaps you have some multicore cable on a roll so you can twist the ends together to double or triple the length.

    Here is a simple chart that shows ohms per meter for all kinds of gauges;


    We only need to know the voltage. An amp meter will change the load resistance unless you have a DC clamp meter.
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    Just sitting in the control room with only the 200 watt panel connected. I'm getting a good 10 amps even through 14 metres of cable, then another 5 metres to the battery and it's not even midday yet. That meets my 20 watts per amp rule of thumb. I'll go to the shed roof in a little while.

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    Not having a DC clamp meter you're not going to like these readings. I also don't have enough wire left to give enough resistance. 40 metres gave only 0.5 ohms. Anyhoo, OC voltage 19.4V. With 40 metres of resistive wire I got 12.9A, volts were low but. Readings taken through high level cirrus.

    Having the whole thing strung together with alligator clips I imagine makes all the readings null and void. I'm not properly equipped to give anything but ballpark figures sorry.

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    Quote Originally Posted by Learjet View Post
    Just sitting in the control room with only the 200 watt panel connected. I'm getting a good 10 amps even through 14 metres of cable, then another 5 metres to the battery and it's not even midday yet. That meets my 20 watts per amp rule of thumb. I'll go to the shed roof in a little while.
    10 amps at how many volts?
    Rule of thumb might be :
    13V battery terminal x 10 amps = 130 watts
    + 1.5 V voltage drop on cable and regulator = 145 watts, which would be pretty close to MPP.
    Last edited by Uncle Fester; 19-02-12 at 01:53 PM.
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    Quote Originally Posted by Learjet View Post
    Not having a DC clamp meter you're not going to like these readings. I also don't have enough wire left to give enough resistance. 40 metres gave only 0.5 ohms. Anyhoo, OC voltage 19.4V. With 40 metres of resistive wire I got 12.9A, volts were low but. Readings taken through high level cirrus.

    Having the whole thing strung together with alligator clips I imagine makes all the readings null and void. I'm not properly equipped to give anything but ballpark figures sorry.
    Thanks anyhow. OC is confirmed.

    Did you actually measure the 12.9A with a multimeter or calculate from the voltage reading?
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