Leisure Batteries Again

Discussion in 'Motorhome Chat' started by Dorwyn, Jul 20, 2015.

  1. Dorwyn

    Dorwyn Funster

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    I think this was fairly well covered recently but I am a little bemused by my LB probs. I have 2 large solar panels totalling a nominal 190 watts, which are presently happily producing 22 or more volts/5amps to the 2x110amp Platinum batteries, but recently the 71 litre compressor fridge has been struggling. When it turns on the voltage from the battery reduces to about 12 volts or less, before building back up to 12.5, this is when the solar panels are not in sunlight. If I charge the batteries at night-time with a mains charger, the smart charger very quickly shows that the batteries are fully charged, as does the power monitoring device I have.

    I am thinking of taking out the 2 LBs and charging them separately, to see if one has partially failed, therefore limiting the other, or if in fact they have both failed. I would establish this by seeing how long each takes to charge to full.

    I have a small Excel meter, but am unsure how to use it to measure the remaining capacity of each battery. It apparently has an ammeter capacity of only 10 amps, unfused, so cannot see how it would cope with a 110 amp battery, or am I misunderstanding this function. How can I establish the remaining capacity, I read about the drop test not really being suitable for the LB.

    The batteries are about 3 and 4 years old respectively, so probably not covered by guarantee.
     
  2. chaser

    chaser Funster

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    I'm no expert but I would be looking at the fridge, I thought they only worked on battery when the engine was running
     
  3. Dorwyn

    Dorwyn Funster

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    It is a 12 volt compressor fridge, no gas or leccy.
     
  4. chaser

    chaser Funster

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    Give up then:)
     
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  5. funflair

    funflair Funster Life Member

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    Put a 5 or 10 amp load on and see how long it takes to go down to 12.2 volts and that should be about 50% of your capacity.

    Should have said fully charged first.
     
  6. Dorwyn

    Dorwyn Funster

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    So the output voltage is a good measure of the amount of capacity left? I take it that is with no load?
     
  7. Dorwyn

    Dorwyn Funster

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    funflair, I note you have an MPPT regulator, I read that they do not operate at less than 18 volts? Doesn't that negate the efficiency improvement?
     
  8. funflair

    funflair Funster Life Member

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    Yes but if the load is too big it will pull the voltage down and then will recover when the load is removed, run them down to about 12 volts and then take off the load and see what they settle at, just record the time under load for your calculation of capacity but remember a 110 ah battery will only give you about 50% of that.
     
  9. funflair

    funflair Funster Life Member

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    I don't know about the 18 volts thing but we have 4 panels the one original is on its own controller and the other three on another, when I fitted three new ones I put these on a MPPT and could watch the performance against the older controller and the old one way about 25 to 30% behind, when I changed the older controller to MPPT the performance of each matched.

    They always generate even if only an amp or two in very poor light.

    Martin
     
  10. Dorwyn

    Dorwyn Funster

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    I probably misread, I do that quite well. That's good to know, I'll pencil an MPPT in - after I've sorted out my batteries.
     
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