Electrical anomalies ? or what ?

Discussion in 'Tech/Mech General' started by MikeandCarolyn, Oct 6, 2013.

  1. MikeandCarolyn

    MikeandCarolyn Read Only Funster

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    Our van is on drive at moment,drained down and 12v turned off.
    We have 2 x 110Ahr leisure batteries and 2 x 80W solar panels. When van is not being used on a daily basis the batteries drop to 85% charge (measured on a NASA BM1 monitor) overnight although no discharge is shown at any time-I have actually checked this on an hourly basis during the night :BigGrin:.
    By midday'ish the solar panels have replaced the charge.
    Yesterday I noticed something which I thought was a bit odd-at 0800 hrs with no sun on van roof the batteries were at 87% and charge was 0.8A at 1100 hrs with low weak sun skimming across panels batteries were ar 94% and charge was only 0.2A.
    Batteries were fully charged as usual by 1400 hrs.
    This morn I checked again-0800 hrs low sun but shadow of house on panels,batteries 86%,charge 0.8A. 1100 hrs batteries 95% low sun now on panels,charge now 0.2A

    I can't make sense of it,unless somewhere I've got summat that reduces the charge rate as batteries approach full charge.
    It did cross my mind that maybe BM1 could need calibrating-but what the hell,I have just checked now (1145) and BM1 is reading 104% :thumb:

    Mike.
     
  2. hilldweller

    hilldweller Funster Life Member

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    Duff battery( ies ) ? How old ?
     
  3. MikeandCarolyn

    MikeandCarolyn Read Only Funster

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    Only 2yrs -Elecsols

    When van is in use,charge is usually around 80% by time we go to bed,having watched dvd,read,used laptops via invertor etc-the charge doesn't go lower during night.
    This loss of charge only happens when van is not being used at all.
    Mike
     
    Last edited: Oct 6, 2013
  4. Reallyretired

    Reallyretired Funster

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    You have. it's called the regulator and it's main purpose is to stop overcharging when the sun shines and you're not using anything.
     
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  5. hilldweller

    hilldweller Funster Life Member

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    Stage one has to be: remove one connection on each and log voltage for a day or two.
     
  6. pappajohn

    pappajohn Funster Life Member

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    the voltage you are getting during the day will be the panel/charge voltage, not the true battery voltage.
    even a known dead battery will show 13/14 volts when the panel is in sun and i would say the batteries are on their way out.

    take readings with panel disconnected and compare
     
  7. MikeandCarolyn

    MikeandCarolyn Read Only Funster

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    Right,I thought regulator wouldn't do that until much nearer to full charge-sometimes this happens around 90% charge which is why I was wondering about calibration of BM1 monitor.
    Also the fact that BM1 reads 104% at moment :BigGrin:

    Mike
     
  8. MikeandCarolyn

    MikeandCarolyn Read Only Funster

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    Full sun (low) at moment and 14v as expected-reading at midnight last night was 12.8v

    Mike
     
  9. pappajohn

    pappajohn Funster Life Member

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    if the BM1 is showing 85% charge AND 12.8v something is wrong with the BM1

    85% equates to 12.45 volts...12.8 volts is 100% charge

    check afternoon voltage with a multimeter then recalibrate the BM1 and check again
     
  10. callumwa

    callumwa Read Only Funster

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    My BM1 also shows 104% when the batteries are fully charged.

    I have read on here and elsewhere that this is a "quirk" of the BM1.

    I also have a Stecca PR 2020 charge controller next to the BM 1 so I can see the actual amps being produced by the panels, and the amount of amps that are being fed to the batteries.

    As the battery nears full charge the amps being fed to the batteries do drop off to somewhere around 0.1 or 0.2 when the batteries are full. This "drop off" usually happens when the BM1 is showing somewhere in the 90's % charge.

    As said already the only way to check if your batteries are ok is to disconnect them completely, leave for a while to let the "float" charge go, then take repeated readings over a period of time to see if the batteries are in good condition or not and holding their charge.

    My wife finds it curious though that I tend to spend more time looking at the BM1 and the Stecca than I do talking to her or watching TV. I must admit I find those numbers moving up and down on those little LCD screens highly therapeutic especially when accompanied by a nicely chilled beverage..:Blush:
     
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  11. MikeandCarolyn

    MikeandCarolyn Read Only Funster

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    I don't think I have any problems actually,was just interested in the way batteries behave differently when having heavy usage to how they behave when standing idle for long periods :BigGrin:
    er,Carolyn has also remarked on BM1 induced paranoia :Rofl1::Rofl1:


    The first meet we ever went on with no EHU we only had 1 battery and relied on 4 LED's on control panel to tell us state of charge-it was -5C and we ran heating constantly all weekend and anything else that we fancied using-we were SO new in those days :BigGrin:
    I often wonder how close we came to disaster that weekend :Rofl1:
    Now,when we are watching TV I am facing the BM1 and flinch every time it loses a % :BigGrin:

    Mike
     
  12. hilldweller

    hilldweller Funster Life Member

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    I think the BM1 is not working how you expect. It can measure all current in and out of the battery so can work in real Ah and not on voltage+temperature. If it's really good it can learn the real battery capacity by comparing volts and the charge/discharge amps.

    I wonder if it has a "actual battery capacity" reading available.
     
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  13. callumwa

    callumwa Read Only Funster

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    Oooops - DP Attack

    My BM1 also shows 104% when the batteries are fully charged.

    I have read on here and elsewhere that this is a "quirk" of the BM1.

    I also have a Stecca PR 2020 charge controller next to the BM 1 so I can see the actual amps being produced by the panels, and the amount of amps that are being fed to the batteries.

    As the battery nears full charge the amps being fed to the batteries do drop off to somewhere around 0.1 or 0.2 when the batteries are full. This "drop off" usually happens when the BM1 is showing somewhere in the 90's % charge.

    As said already the only way to check if your batteries are ok is to disconnect them completely, leave for a while to let the "float" charge go, then take repeated readings over a period of time to see if the batteries are in good condition or not and holding their charge.

    My wife finds it curious though that I tend to spend more time looking at the BM1 and the Stecca than I do talking to her or watching TV. I must admit I find those numbers moving up and down on those little LCD screens highly therapeutic especially when accompanied by a nicely chilled beverage..:Blush:
     
    Last edited: Oct 6, 2013
  14. pappajohn

    pappajohn Funster Life Member

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    we both know there is only two ways to determine a batteries capacity at any given time....unloaded voltage or hydrometer.

    amps are 'invisible' unless measured under load...inwards or outwards.

    if you could simply connect a meter to a battery and display remaining capacity then eBay would be full of them.
     
  15. hilldweller

    hilldweller Funster Life Member

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    Isn't that exactly what the BM1 does, doesn't have a shunt in the battery neg ?

    Or is that the Nasa one ?
     
  16. pappajohn

    pappajohn Funster Life Member

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    same item Brian....NASA BM1

    the 100amp shunt is to measure incoming/outgoing amps...not capacity.

    this taken from a previous post and approved/liked by Eddievanbitz no less



    it only shows amps by reading, very accurately, volts remaining, then a simple calculation converts to amps.

    12.7 volts is fully charged (100%)...12.1 volts is flat (50%)...if it sees 12.4 volts it knows its half discharged from its fully charged state and if it knows the battery is 110ah, as you 'told' it, then it shows 55amps.
     
    Last edited: Oct 6, 2013
  17. pappajohn

    pappajohn Funster Life Member

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    the BM1 is only as good as the human programmer and is easily fooled.

    connect it to a 200 ah battery but program it to 'see' a 100 ah battery and it will show 'capacity' for a 100 ah battery

    200ah battery at 50% discharge will show on the display as 100% charged....because it been told its a 100ah battery.
     
    Last edited: Oct 6, 2013
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