Leisure battery advice

Discussion in 'Motorhome Chat' started by Pikeman, Jul 31, 2012.

  1. Pikeman

    Pikeman Funster

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    Hi Folks,
    My van is secondhand and I think the leisure batterie's (have a pair), are the originals, therefore 10 years old. Still functional, but not as good as I think they should be. My question is how do I test them to determine if I should replace? :Cool:
     
  2. Wildman

    Wildman Read Only Funster

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    you could take them to a garage and have them tested with a discharge tester.
    You could make sure they are full charged then disconnect them from the van and each other and check the voltages after 1 hour, 24hrs and one week. make a note of the readings and see what you get.
    Youu could also check the specific gravity of each cell if you have the appropriate tool to check for differances (lead/Acid only).
    If lead/acid make sure they were fully topped up before charging
     
  3. Pikeman

    Pikeman Funster

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    Taking to a garage at intervals sounds impractical. What is a discharge tester? Googling sugests a multimeter, but I am vague on the subject. Come on folks 42 read's and only one feedback - you can't all be watching Phelpes!!
     
  4. jonandshell

    jonandshell Funster

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    As Wildman said, you need to fully charge the batteries, check the open circuit voltage and the specific gravity of the electrolyte.
    You should get 12.8V and an SG of approx 1.265 if the battery is healthy (at 20 degrees C)
    Remember to get rid of the 'surface voltage' on the battery by briefly putting a load on it.

    If you have sealed batteries, then a performance test by draining them at a known amperage over 20 hours is the only way to ascertain if they match the original performance.

    Most batteries are rated at a 20 hr rating.
    Ie a 100Ah battery will give 5amps for 20 hrs for a 100 % diacharge.
    Discharging to this level is not recommended, however because going beyond this will damage the cells. As a rule. discharge leisure batteries to 50% max (open circuit voltage 12V).
    Therefore, for testing, discharge the said battery at 5 amps for 10hrs and then measure the open circuit voltage. This should now be 12V if the battery is healthy.
    Using the power formula, to get a discharge of 5 amps from a 12V battery, you need a 60W load. A 50W bulb is close enough for this and makes a readily available test apparatus!:thumb:

    If you have traction batteries, 11.6V (80% discharge) is fine.:Smile:
     
  5. pappajohn

    pappajohn Funster Life Member

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    the old fashioned, and best, version. HERE

    the new digital version....crap in my opinion. HERE

    you dont need to take to a garage at regular intervals.....just check the voltage after 24hrs, one day and one week with a cheap multimeter.

    12.7v and above after one hour off charge = 100% charge
     
  6. Gooney

    Gooney Funster

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    Your right Paps, the drop tester is best, it induces a load situation on the battery but at £100 plus not the bit of kit Joe average carries, if you take your batteries to a local tyre battery dealer they will test using a drop tester for you for free!!
     
  7. Reallyretired

    Reallyretired Funster

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    All very complicated. I don't think you'd want to spend £100 on a discharge tester. Suggest you could connect the fully charged battery to a car headlight bulb (55w) which you can get for under £2 which will draw around 5 amps. If its still bright after 10 hours (110Ah battery, 8hrs 85Ah battery) then your batteries are fine, if it dims after a few hours then they need replacing. Don't run it for longer than this though or they will need replacing anyway through over discharging. Take care the bulb will get very hot.
    Alternatively if you're sure they are 10 years old they will almost certainly need replacing anyway. If still readable there should be a date on the batteries.
     
  8. pappajohn

    pappajohn Funster Life Member

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    I wasnt suggesting the op went and bought a £100 drop tester....simply answering his question "what is a discharge tester" :thumb:
     
  9. Pikeman

    Pikeman Funster

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    :thumb: Thanks everyone, Ive learnt stuff tonight! Will act on your advice.

    This is why I joined this community!
     
  10. Snowbird

    Snowbird Funster Life Member

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    Machine Mart do a good drop tester for around £30 if I remember right. Its some time since I bought mine and its well tried and tested. Not digital, it has a meter on the front and 2 crocodile clamps that attach to the battery with a heating element inside. Good piece of kit and will pay for itself over time.

    Good news, have just checked and its £23.98 and its the CVT1 model you want.
     
    Last edited: Aug 1, 2012
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