Checking Battery

Discussion in 'Tech/Mech General' started by Schnauzer, Oct 1, 2009.

  1. Schnauzer


    Sep 27, 2009
    West Sussex
    I have just been monitoring my leisure battery before our first wild camping trip. When fully charged it shows a steady 13.4v but under load it obviously drops according to what I turn on. What my question is, do I check my battery when there is no load and settles? And just to confirm - I don't really want it to go below 12.2v? (BTW its a 110 batt)


  2. Tony Lee

    Tony Lee

    Sep 28, 2008
    The 13.4 is about normal float charge voltage so either you have a fixed voltage converter that doubles as a semi-charger, or you have a three-stage charger that has gone through the different cycles to finish on float.

    If you disconnect shore power, the battery voltage will drop over two or three hours to its no-load resting voltage of around 12.7 give or take depending on temperature, type of battery and whether or not it is fully charged. There must be no load and no charging going on for several hours before taking the reading.

    Use an accurate digital multimeter and refer to the table of resting voltages applicable to your battery to get a reasonable idea of how fully your batteries are charged.

    Not going below 12.2 is a good idea, but this also needs to be measured when the battery is resting. If you are dragging a lot of current out to feed an inverter then a voltage under load of say 11.5V might correspond to a resting voltage of 12.2V so it is not something that is easy to judge without a lot of experience with your particular set-up

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