Output?

Discussion in 'Solar Power' started by ShiftZZ, Jul 24, 2013.

  1. ShiftZZ

    ShiftZZ Funster Life Member

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    We have 2 x 80 w solar panels and a meter which tells me some info..

    One is watts, that ranges from 10'sh to 85w. The second one is amps at that has been as hight as 5.2A.

    Without going too techie, should I be looking at the Amps or Watts or Volts?
     
  2. Bailey58

    Bailey58 Funster Life Member

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    I don't know a lot on this either but I would be interested in how many amps the panels are putting into the batteries, 5.2? Sounds good but I would think it should be in this sunshine. :Smile:
     
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  3. capinpugwash

    capinpugwash Funster

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    Without getting too techie I believe that amps are the important measure. Output or use is measured in amps, and input should be measured the same way.

    What you take out you put back!!!

    Volts and watts are related as well (Ohms Law) but with batteries in Motorhomes amps are king, except when measuring the health, when volts rise to the fore.

    Opinions will vary, watch this space:BigGrin:
     
  4. tonka

    tonka Funster Life Member

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    Amps would be the best..
    Think of it this way... Example, You have a battery that holds 100amps when full, the figure you are looking at is based per hour so if the panels are doing 5amps it will take 20 hours to completely "fill" a battery..
    Now you never empty the battery, 50% at worst case to avoid damage and you never get the same filling rate.. But it gives you an idea of whats going in...

    As Stuart says, amps, watts , volts are all related and you could convert amps into watts but amps is easier in this case..

    Ref taking power out, most items are rated in watts. So a conversion is needed if you want to compare in amps.
    ie a TV could be 40 watts.. Using the famous Ohms law. divide watts (40) by volts (12) gives 3.33 amps....
     
    Last edited: Jul 24, 2013
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  5. BwB

    BwB Funster Life Member

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    Unplug from electric hook up, turn on everything electrical in the van you can find. Wait 20 minutes and then look at your solar output reading.

    If your batteries are already "full" then the draw from the solar panels is just going to be a maintenance charge - mine shows 0.4A. But yesterday after I'd had the TV running, turned all the lights on, etc. in full sunlight it was showing 5.2A for what I think is a single 80 solar panel. As the batteries topped up the Amps went down until about an hour later the reading was back to 0.4A

    PS - it's either Watts or Amps to show you what's going into the battery. The Voltage just shows the state of the battery.
     
  6. buttons

    buttons Funster

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    Secondary modern electrical theory.
    [FONT=&quot]Water flow is amps, water pressure is volts, watts is a calculation of both allowing for the pressure or voltage variables which can change at either end of the hose or circuit. So if you just want to know the throughput then amps or the water meter is your choice.:thumb:[/FONT]
     
  7. hilldweller

    hilldweller Funster Life Member

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    That's interesting, you have never gone above 50% then.

    Now having them flat loses 25% for a start.

    If your batteries are charged then it backs off the current, so that 5A is negotiable, you need to turn on more than 5A of load to make the cells give their maximum reading.
     
  8. buttons

    buttons Funster

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    Sounds like you agree with my theory then.:thumb:
     
  9. SomeoneElse

    SomeoneElse Funster

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    ShiftZZ,

    I will try to answer your original question, based on using your panel to charge your battery with no other power usage.

    You should look at both the volts and amps; volts first then amps, you can then conclude:

    1. With rising voltage:
    Anything from 12V to 14.4V, the controller will be busting a gut to charge your battery and the amps will be the maximum available from you panel.

    2. At a constant 14.4 volts:
    Your battery is nearly full and the amps will be decided by what the battery needs to complete the charging process. The current will be less than the maximum available from the panel.

    2. At constant volts of 13.7 and very small amps:
    Your battery is full and the small Amps ( possibly zero ) is all that is necessary yo keep your battery brimmimg full.

    Its only in state one where you can look at the Watts and compare them with the size of panel you were sold.

    Gordon
     
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  10. haganap

    haganap Funster Life Member

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    Sorry but what a load of daft answers. :BigGrin: And you Hilldweller!!! I think you would know better :Wink:

    Shiftz, all of us solar panel experts know the truth.

    step out ya van.... Look to the sky....Indian chief says the following......

    Big Sun = Big amp = big battery

    Cloudy sun= Not big amp = smaller battery

    No sun= tiny amp = turn telly off.

    Dark outside = No amp = Oh sh*t time for bed. :thumb:

    hope that helps.
     
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  11. ShiftZZ

    ShiftZZ Funster Life Member

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    Right, here we go with my Comprehensive school education.
    We have three ‘devices’ for measuring voltage, one for the Van battery, one for the habitation and a separate one fitted for the solar.
    The Van battery is usually about 12.8v the same panel also measures about the same, even 1st thing in the morning and when the sun is out we get 13.7v or something.
    The watts on the meter varies from very small (even when the panels are covered on snow) to well over 100w,it could have been around 248w!!! which is what I managed last year in Lyon. The Amp measurement was last spotted when we were in Stratford on Avon.
    We have never ever gone below 12.5/6v.

    All I was wondering was did any of these readings point to the efficiency of the solar panels?

    See attached pics, they don’t ,make any sense.. They were taken last year...
     

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  12. hilldweller

    hilldweller Funster Life Member

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    Not for me you b^^^^^d, I'd got away with sprouting drivel until you came along.
     
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  13. hilldweller

    hilldweller Funster Life Member

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    Your battery is 13.9V and it's pumping in 17.8 amps and you've recorded 18.1 hours of sunshine ( since when ?? ).

    Now 13.9 x 17.8 = 247W

    That pretty good from a pair of 85W panels.

    So meter a waste of space or have you got a load of panels you didn't know about ?

    Each panel should be good for a theoretical 5A.
     
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  14. littlehouse

    littlehouse Funster

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    Cheap metering !!!

    I've just bought a couple of handy devices on ebay (item no. 181137155880 will take you to this seller) which seem to be able to provide all this information, depending on which (easy) settings are programmed. This includes volts,amps watts whilst charging or discharging and also can display battery charge level and endurance etc. These are fairly cheap (20 quidish) and depending on the specific model, can handle your whole battery input / output, or when connected to an old fag lighter plug, will act as a simple voltmeter when plugged into the vehicle or house circuit. These are also quite small, so can easily be fitted permanently. These come from China within a few days.:thumb::thumb::thumb:
     
  15. Chris

    Chris Funster Life Member

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    x-y =q

    Bloody obvious:thumb:
     
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