Converting volts to amps

Discussion in 'Tech/Mech General' started by Welsh girl, Dec 22, 2013.

  1. Welsh girl

    Welsh girl Funster Life Member

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    How many amps are in a volt?
    Our batteries has gone down to 11.6 volts, the solar panel hasn't been doing its work.
    we bought a multimeter to check our usage and only using a freesat box to watch prerecorded films as we can't get a signal here in Portugal.
    We also use an led tv.
    Led lights except for the bathroom 2 fluorescent bulbs, normal use on the pump, no battery charging, no hook up.
    So on the multimeter we are using 3.6 amps a day.
    The multimeter read that only 0.1 amp was put in all day (8 hours very sunny day)
    we have 2 x110 leisure batteries, 85w solar panel, surely they shouldn't be reading that after just 3 days ?
    So the question is...as the batteries are reading 11.6...started off at 13.4 ...how many amps...not volts.. have we used?
     
  2. John Laidler

    John Laidler Funster

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    Oh gosh, where to start? Read this. http://science.howstuffworks.com/environmental/energy/question501.htm

    But I suspect the problem is the time of year. Your solar panel only produces maximum power with the sun directly overhead. At this time of year with low sun angles and short daylight hours it will struggle to produce 10% of what it would on a summer's day, even in Portugal.

    Worth checking your solar panel is clean and how old are your batteries? They deteriorate with age.
     
    Last edited: Dec 22, 2013
  3. Larby

    Larby Funster

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    Amps in a volt?? that's easy, NONE
    I would reckon you answered your own question, Panel or wiring ?
     
  4. tonka

    tonka Funster Life Member

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    The first thing I would do is look on the back of your TV.. see how many watts it is, almost all electrical appliances have a label....
    example if it is LED it may use something like 20 watts...
    So you divide 20 (watts) by 12 ( the volts supplied from your battery).... = 1.66 amps

    So your TV consumes 1.66 amps PER HOUR....
    Do the same with the freeview box, and other things and you should be able to guesstimate your usage..

    An 80w panel at its very max peak will put in 4-5 amps per hour in very good sunlight.
    In reality a lot less..

    You say you are using a multimeter but how are you measuring the amps ??
    You cannot just place the meter across the two terminals, for amps it needs to be in line, so dissconection of the +ve wire..

    Either you are drawing more than your solar is puttting in.. or fault on batteries or fault on solar system..
    My first action would be to check voltages coming into the regulator and the output of the regulator.. If those are correct then it eleminates the solar equipment,,


    Good luck..
     
  5. MikeD

    MikeD Funster

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    I am no expert

    Amps = load on the battery so if you have measured the load from your battery at 3.6 amps. This is only the load at that time of measurement and not a average throughout the day. Your actual load can vary hugely.

    Your solar panel will put out around 4 amps whilst the sun is out.

    So your solar panel will probably keep up with your useage during the day but at night you will be drawing from the batteries.

    Your batteries are 110amp/hour x2. So 220 amp/hours. You can't discharge that all but around 50% seems to be recommended.

    So 110 divided by 3.6 would give you somewhere around 30 hours before they are becoming very discharged.

    Volts x amps = watts

    so if you look at the label on the TV etc. it should state how many watts it needs to operate. A small LED TV may draw 40 watts in use but still 20 watts while switched off but plugged in.

    Add all the "watts" of everything you use. Divide the number by 12 (volts) and that should give you how many amps your are loading on the solar panel/batteries.

    Amp/hours are how much you are using during a hour.

    I have probably got it all wrong but I am sure someone with more brains will put me right. At the very least I have bumped your thread

    I hope this helps
    Mike :thumb:
     
  6. Welsh girl

    Welsh girl Funster Life Member

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    No standby, we make sure all plugs are out when not in use, even 12v sockets.

    New batteries and solar panel, (August 2013)

    free Sat box 50w led tv 30w so not much usage there.

    I didn't know how to use a multimeter, Steve here on the site told me that if I placed the turn around knob on the multimeter to 20 dvc and then red to positive and black to negative that should give me reading.
    How can we check solar panel regulator is working?
    Terry cleaned solar panel Tuesday.
     
    Last edited: Dec 22, 2013
  7. Larby

    Larby Funster

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    Disconnect leads from controller to leisure battery, then check voltage across the ends, (keep them apart) !! Is it sunny there?
    Have you an in-line fuse from controller to leisure battery? It may be blown?
    My guess is failure to charge sufficiently or at all rather than 2 batteries going kaput.
     
    Last edited: Dec 22, 2013
  8. Larby

    Larby Funster

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    It may be wise to go for a run so the alternator can put a bit back into those batteries. Don't leave them low.
     
  9. hilldweller

    hilldweller Funster Life Member

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    In blazing summer sunlight at noon you might get 85 / 12= 7A.

    In winter you'll be lucky at 1A.

    Your 80W of TV is 80 / 12 = 6A

    So 1A in and 6A out, it's not going to work.

    You'll have to go for a run and use the engine to charge your batteries up.
     
  10. Wildman

    Wildman Read Only Funster

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    I'm afraid that will blow the solar regulator. ALWAYS Disconnect the solar panel from the regulator before disconnecting the battery. the voltage across the two open leads with nothing attached leads should be around 17v.
    It really all boils down to how much power you are using and how much the solar panel is putting out. At this time of year it may not be much more than 1amp per hour in Portugal conciderably less in the uk
     
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  11. Welsh girl

    Welsh girl Funster Life Member

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    Very warm and sunny here, 8 hours uninterrupted sunshine, so I would have thought some juice would have been put in, battery down to 11.15 this morning, before Sun came up too far.

    Will check to find out if controller has in line fuse, if I can find it?
    The dealer Marquis installed the batteries and solar panel so it's anyone's guess where it is ?
     
    Last edited: Dec 22, 2013
  12. pappajohn

    pappajohn Funster Life Member

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    at the time of connecting your meter you were using 3.6amps per HOUR..not per day.
    this will change as items are turned on and off.

    again, at the time of connecting the panels are charging at 0.1amp (100milliamp) per HOUR

    I would expect slightly more than that even in winter with a low sun....at least 0.5amps/hour....but still a useless amount as you were using 36 times more than the panel was putting back in.

    is your panel in any shadows...building, trees etc ?
    that can and does have a dramatic effect on charge current.
     
    Last edited: Dec 22, 2013
  13. peterc10

    peterc10 Funster

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    As others have said you are simply using more power than your solar panel is generating and can ever could generate in the circumstances. Even if it is warm and sunny down there in the winter the lower angle of the sun means that their is a lot less solar energy falling onto the solar panel.

    If your figures are correct your TV and box are using a lot of energy. A simple formula is volts x amps = watts. So 80w at 12v = over 6 amps. But you will get a lot less than that on average from your solar panel. And at that usage it will not take long for your batteries run down.

    I suspect in the short run you have three options. Go for a long run in the van, get a hook up, or use less energy.
     
  14. John & Joan

    John & Joan Funster

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    I am near Vera in southern Spain

    My 240w of Solar produced
    15Ah on 19th peak 5.23amps
    6.3Ah on 20th peak 2.75 amps and
    10.2Ah on 21st peak 5.25 amps (the shortest day).

    In summer in the UK I have had 128 Ah peak on a summers day.

    Amps x Volts = Watts
    Watts / volts = Amps

    It takes 1 Volt to push 1 Amp through a 1 Ohm Resistance
     
  15. John Laidler

    John Laidler Funster

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    I would suggest, before you start disconnecting anything at around mid-day turn everything off for an hour or so. If everything is working the battery voltage should creep up a bit and the panel should show a small charging current, perhaps an amp or so, but the control panel itself will also be taking power so not all the current generated by the solar panel will go to the batteries.

    85W is not a big panel by modern standards, most people use more like 100W and if you want to be off grid in winter for long periods you really twice that or more ideally.
     
    Last edited: Dec 22, 2013
  16. Wissel

    Wissel Read Only Funster

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    That's around 6.5a per hour.

    You have around 110ah of usable battery (if you use the 50% guide, on a lot of batteries if you discharge further than this it will damage them, maybe kill them).

    Just your TV set up will drain your batteries in under 17 hours.

    Edit - By the way, at 11.6v your batteries are flat, way under 50% (which I think is about 12.2v from memory) so it might be worth having them checked if you have a garage somewhere close by.

    Also, your TV set up uses a lot of power. I have a PC with a 24" screen running in my van and it uses about half the power of your set up. Might be worth looking for a lower power box in the future.

    Do you have a descent charger on your van from the engine? If so can you run the engine for a hour or so to get some charge?
     
    Last edited: Dec 22, 2013
  17. pappajohn

    pappajohn Funster Life Member

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    it isnt the amount or brightness of the sun....its the suns angle to the panel.

    with the sun at 90deg to the panel it will be maybe 90% efficient...it will never be 100% except in theory.

    With the sun as low as it is now it may only be 5% efficient if that much.

    And from your previous post....



    So the question is...as the batteries are reading 11.6...started off at 13.4 ...how many amps...not volts.. have we used?

    11.6v is technically a dead battery, in fact slightly over discharged.
    10volts and it time for the bin...it wont recover.

    I would extimate you used 120amps

    common consensus states a battery should never be discharged below 50% capacity and you have a total of 220ah therefore 120amps used or 55% used
     
    Last edited: Dec 22, 2013
  18. callumwa

    callumwa Read Only Funster

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    Your battery is now seriously discharged, dangerously so, and it is on the way to the Battery Graveyard.

    Go for a good long run.... NOW..... otherwise you may find you are buying new batteries for Xmas.......


     
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  19. pappajohn

    pappajohn Funster Life Member

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    to continue winter camping as you are you're going to need.....

    a...more batteries....but that means more charge current

    b...another solar panel....bigger the better but still may not give enough charge.

    c...a generator....noisey and need to carry petrol

    d...a battery to battery charger....which means starting the engine for an hour or more

    e...stay on campsites with hookup
     
    Last edited: Dec 22, 2013
  20. tonyidle

    tonyidle Funster

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    At this point, assuming standard charging arrangements when the engine is running, you are way past the point where a 'good run out' will charge your batteries. To re-charge them fully will require a 30 hour+ drive. To ensure that they survive you need a hook-up for 2 to 3 days to guarantee a full charge.
     
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