problem with solar battery

Discussion in 'Designing, building, making and powering your life' started by pebble, Mar 17, 2008.

  1. pebble

    pebble Junior Member

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    I have a deep cycle battery charged off a solar panel on my housetruck. I've been away for a couple of months, and when I got back 2 days ago the voltmeter was showing 14V (normal). However once it got dark and I turned on a light the charged dropped to less than 8V within half an hour. Same thing last night. But it charges up fine in the morning so I can listen to the radio and use the water pump.

    Any ideas what's going on? Is the battery stuffed and I'm just getting a small charge in the day from the sun but it's not building up? Anything I can measure to tell me more what is going on?

    The solar/house battery is connected to the truck battery and will charge off that, but there's been nothing on in the truck electrics afaik and the truck battery shouldn't drain the solar one. Can't think of anything else except that maybe there's some house wiring not right or something like that that is draining the house battery.
     
  2. dgriffith

    dgriffith Junior Member

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    It does sound like it's done its last cycle, especially if it goes to 14V and then drops to 8 overnight with bugger-all load on it. How old is it? Have you run it flat much?

    A few things to check :
    - Give the battery a (gentle!) rock back and forth to stir the cells a bit.
    - Check the cells for adequate water.
    - Check that one of them isn't unusually low or dirty compared to the rest - if there is, you've likely got a dud cell,and a new battery is needed.
    - Check for "fizzing" when under charge. Again,all cells should bubble/fizz equally. One that's going a lot more or less than the rest means, yup - dud cell.
    - Do a (careful!) sniff test when charging - if you can smell rotten-egg gas (Hydrogen Sulphide) , it's a bad sign. Do be careful though, don't poke your face into the top of the battery, just use your hand and waft a bit of air towards your nose from it.
    - Get a battery hydrometer ( a glass thing with a squeeze-bulb and float inside ) Normally about $10 from your servo/car parts joint. Suck a liitle out of each cell and make sure they all read the same on the float. If one's much higher/lower - dud cell.

    That pretty much covers the basic checks - hope that helps.
     
  3. pebble

    pebble Junior Member

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    ok, thanks, I'll try that out.

    I did let it dip down below 11 V sometimes over the summer, but never as low as 8. Does that count as running it flat?

    I'm not sure how old, maybe 3 years?
     

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