How much power should I be getting?

Discussion in 'Solar Power' started by Feltwell, Feb 15, 2015.

  1. Feltwell

    Feltwell Funster

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    My secondhand van came already fitted with a solar panel on the roof. The habitation battery is, I think, not in the best of condition - the battery is discharging such that every couple of weeks I need to hook the van up to the mains, before it discharges completely, despite the solar panel putting charge in every day. The only draw on the habitation battery is a small digital clock.

    On a day like today - cold, overcast & cloudy, van parked between buildings but not in shade - I've typically been getting 0.3A going from the solar panel into the battery, according to the control unit. The panel has no indication of wattage on it, but as it's 650 x 1450mm, looking at websites selling panels I'm guessing it's a 120w unit. Does 0.3A in these conditions sounds about right?

    I'm hoping that once the habitation battery is changed, the panel will in winter provide enough input to keep both the habitation and vehicle batteries charged - stop the alarm flattening the vehicle battery. They are linked with a Sterling battery maintainer, but at the moment that's not really doing much as the voltage in the habitation battery drops too low for it to switch on.
     
  2. Minxy Girl

    Minxy Girl Funster Life Member

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    Unfortunately at this time of year there's no way a solar panel will keep your batteries topped up on it's own, unless it is massive! We have a 75w panel on our van's roof and don't have any draw on the van's power normally, but still have to put it on hook-up every 2 weeks to ensure that the batteries don't get below 50% discharge (this can permanently damage them).
     
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  3. Wickolad

    Wickolad Funster

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    Sorry I cant give you much info with this but in this sort of weather dull and overcast there isn't a lot of output from panel and even then, there are variables that can have a drastic effect such as dirty panels, shadowing etc. 0.3a/h though is very little, 8 hrs daylight is only going to have achieved 2.4a charge at whatever voltage the controller is putting out. I'd probably disconnect the clock, get the battery charged up fully with a decent multi stage charger before putting back in van then see how it goes. Just ensure theres nothing drawing current and it may just be enough to tick over.
    Summer months are much better obviously. But you may have to wait till we get some decent sunshine before you get a good idea how well the panel is performing. I'll have a check on mine tomorrow, see what output is with 2x 100w panels with a mppt controller and let you know. (y)(y)
     
  4. DP_JAY

    DP_JAY Funster Life Member

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    I suspect your battery is past it's best. We have 2 x 80w panels which easily maintain 3x110amp batteries plus the cab battery all winter with no need for hook up, the only time the batteries fell bellow 12.7v was when the panels were under snow.
     
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  5. Bobby22

    Bobby22 Funster

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    I don't know much about solar......but i would check the battery before you discard it, it may well need only topping up.
    Take the cap from each cell and check that the plates are covered with acid......if not.......top up with water......and give it a full charge.

    It may hold the charge better if this is the case.
     
  6. Cal54

    Cal54 Funster Life Member

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    I have a 100 wt solar panel and it has kept my 2 100 amp leisure batteries topped up ok. The van has been stood for nearly 10 weeks with only one day trip in that period, and when checking the batteries yesterday everything was ok. Mind you we have had some great sunny days in Lancashire over the last week. Would suggest you check the battery first.
     
  7. Daifuse

    Daifuse

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    Same here, in bright sun today my panel is only putting out 100mA - the batteries showing almost 14v.
     
  8. gillnphil

    gillnphil Funster

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    2 x 120 watt solars, hooked up to 2 Exide G 80 leisure batts keep them fully charged up over winter with no need for electric hookup.
    Phil
     
  9. pappajohn

    pappajohn Funster Life Member

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    120w panel will, in theory, give you 10amps
    in the real world that may be 7amps in high summer with the sun overhead.
    this time of year i wouldnt expect much more than 500ma....the sun is too low to be of much use.
     
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  10. Jimbohorlicks

    Jimbohorlicks Funster

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    I checked my 2 x 100 watt panel output on Sunday and it was pushing out 0.6-0.9amps--if that info helps ( van is parked on drive slight overhang from some branches to one panel and sloping down away from the sun -ie worst angle approx 20 degrees down)but sunday was better day
     
  11. Trikeman

    Trikeman Read Only Funster

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    Our two 100w panels feeding through MPPT to two 110ah leisure batteries - batteries fully charged all over winter. Used yesterday and all electrics 'up and atom' running heater blowers, loo flush, water pumps and TV for a few hrs - both batteries fully charged by the time we got home and that was solar only charging.
    Never used an EHU since we fitted the system.

    Regards,

    Trikeman. ;)
     
  12. Funnymunny

    Funnymunny Read Only Funster

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    One 120 watt solar panel keeps my two 105 amp batteries toped up plus my starter battery and runs the alarm all winter without any other use. If you have a 120 watt panel you should be getting much more than .3 of an amp unless it is really dull al day long.
    I would expect it to show at least 1 amp on a dull day and any sun at all up over 3amp to 5 amp this time of year.

    I am in Portugal at the moment and mine tends to top out at 5.4 amp this time of year but hits 8 amp easily in summer even in the UK.
     
  13. Lenny HB

    Lenny HB Funster

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    This time of year and hour or so either side of midday I get a bit over 2 amps from my 2 x 100 Watt panels on the south coast. You say your van is parked between buildings this limits the hours of useful power as the van will only be in direct sun part of the day, a shadow over only a very small area of the panel will drastically reduce the output.

    The battery sounds like it's well past it's sell by date, best to get that sorted first.
     
  14. NickNic

    NickNic Funster Life Member

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    We have 200W of solar and 2x110ah leisure batteries and they've been fine all winter. We can last indefinitely with no EHU and our normal usage, the solar more than copes
     
  15. NickNic

    NickNic Funster Life Member

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    We have 200W of solar and 2x110ah leisure batteries and they've been fine all winter. We can last indefinitely with no EHU and our normal usage, the solar more than copes
     
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