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Cheap ebay solar module quality/performance ? — Parallax Forums

Cheap ebay solar module quality/performance ?

CuriousOneCuriousOne Posts: 931
edited 2014-06-22 07:41 in General Discussion
Hello.

I'm building a remote weather station, and want to use solar power as battery charge source. I've checked various ebay offers and they all seem to differ quite much. For example, one seller has 55x55mm module, rated at 2V 30mA. Another has 65x65mm module, rated at 5.5v 90mA. Which one is more close to real numbers?

Comments

  • SapphireSapphire Posts: 496
    edited 2014-06-15 00:34
    Convert the output power to mW per square cm to compare. The first is only 2mW per square cm, pretty low. The second is 11.7mW per square cm, better.

    I built a solar powered weather station with battery for nighttime operation and used a 9V 167mA (1.5W) solar panel that is 130mm x 85mm for 13.6mW per square cm. This is more than enough power for the sensors, processor, transmission and keeps a 6V SLA battery fully charged. It can run a month without sunshine.
  • CuriousOneCuriousOne Posts: 931
    edited 2014-06-15 00:44
    So I can estimate, average efficiency of such cels ase 12mW/Square CM ?
  • FranklinFranklin Posts: 4,747
    edited 2014-06-15 11:25
    So I can estimate, average efficiency of such cels ase 12mW/Square CM ?
    I'm not sure I understand the question.
  • CuriousOneCuriousOne Posts: 931
    edited 2014-06-15 22:45
    Chinese enjoy providing fake data with product they sell. AA battery can be 300mAh, but branded as 3000 mAh. Same with solar cells. So, averaging by size, which power I should expect from samples above?
  • GenetixGenetix Posts: 1,758
    edited 2014-06-16 11:17
    Pay attention to the test conditions if they are stated since I am sure that some companies will choose conditions that will give exceptional results.
  • GadgetmanGadgetman Posts: 2,436
    edited 2014-06-16 15:36
    With Chinese components on eBay, just assume the worst. Then you probably won't be too disappointed...

    Solar panels is one product it really pays to buy from reputable sources.
  • CuriousOneCuriousOne Posts: 931
    edited 2014-06-22 00:55
    Bought this lot:

    http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=231261456221

    Seller promises 2V 30mA max.

    Hooked them 5 in series, wiring checked and separately all panels also checked to be fully functional.

    Connected to ammeter and put into midday strong sunlight. Delivered current was 17.4mA and voltage - 5.5v, for 5 modules hooked in series. Under no load, each module delivers 2v as promised, but 17mA current is nowhere close to promised 30mA. Tried with single module, used large freshnel lens to focus light on single module, no change, current is still low.
  • Heater.Heater. Posts: 21,230
    edited 2014-06-22 02:25
    If the spec is "30ma max." then 17.4ma is correct :)
  • ercoerco Posts: 20,257
    edited 2014-06-22 07:41
    Did you remove the plastic scratch film on top? Might be good for a few mA.

    US seller might be motivated to help. If output is half promised, ask for half refund or another free set.
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