One for the electrical gurus

Discussion in 'Solar Power' started by MikeandCarolyn, Apr 8, 2011.

  1. MikeandCarolyn

    MikeandCarolyn Read Only Funster

    Joined:
    Mar 18, 2008
    Messages:
    2,171
    Likes Received:
    1,463
    Location:
    Worle,North Somerset
    We have 2x80w solar panels and a NASA BM1 Battery Monitor-last year we had 1x110Ah battery and whether on EHU or solar we would get a reading of 105% when battery was fully charged.If on solar this would usualy be achieved by 10.00 hrs regardless of how low it went by bedtime.
    Now we have 2x110Ah batteries and every thing else is the same.On EHU we get a reading
    of 105% as before,but on solar it only goes up to 85% and stays there. Today,in bright sunlight,I was getting 20.2 volts from the solar panels. I switched the TV on and ran it till I was getting 70% charge on the BM1 then switched it off and the % climbed back to 85% in about 15 mins but didn't go any further.
    Why this anomaly in readings ?

    Mike.
     
  2. pappajohn

    pappajohn Funster Life Member

    Joined:
    Aug 26, 2007
    Messages:
    29,463
    Likes Received:
    16,900
    Location:
    YO11 2BD
    i could be talking bo//ox Mike and im sure someone will say so but....

    i think it may be down to the type of solar controller you have.

    PWM or MPPT

    PWM isnt as efficient as MPPT and may be struggling to charge your 220ah battery bank to full capacity.

    just as a standard battery charger will usually only charge to around 80%/85% i beleive the PMW is about the same.

    worked fine with one 110ah battery as it only had half the work.

    as an afterthought.....do you need to set any parameters into the BM1 ?
     
  3. MikeandCarolyn

    MikeandCarolyn Read Only Funster

    Joined:
    Mar 18, 2008
    Messages:
    2,171
    Likes Received:
    1,463
    Location:
    Worle,North Somerset
    It is a PWM controller :BigGrin: and I have set 220Ah as the capacity in the BM1- It was in the back of my mind that by increasing the number of batteries I was giving the system more work to do. Think you've cracked it-hopefully :BigGrin:

    Mike
     
  4. Geo

    Geo Trader - Funster

    Joined:
    Jul 29, 2007
    Messages:
    9,521
    Likes Received:
    5,573
    Location:
    Mansfield,Notts
    Yes John he should re calibrate the BM1 to his new system using known fully charged batteries
    Geo
     
  5. MikeandCarolyn

    MikeandCarolyn Read Only Funster

    Joined:
    Mar 18, 2008
    Messages:
    2,171
    Likes Received:
    1,463
    Location:
    Worle,North Somerset
    I had discussed the problem with Sunshine Solar and told them I suspected that the controller I had was not performing properly-they sent me a replacement today which I have installed with the same results-I now see that they also sell a MPPT controller and claim a 30% increase in efficiency for it !! Why didnt they suggest that earlier Grrr.

    Mike
     
    • Like Like x 1
Loading...

Share This Page