Newbie question

Discussion in 'Motorhome Help for the Beginner' started by crimbo, Aug 5, 2013.

  1. crimbo

    crimbo

    Joined:
    Aug 5, 2013
    Messages:
    25
    Location:
    Hampshire
    Ratings:
    +8
    Hello peeps,
    Am I right in assuming that the leisure battery is charging when the motor engine is running or the 230v mains is connected :Smile:
     
  2. pappajohn

    pappajohn Funster Life Member

    Joined:
    Aug 26, 2007
    Messages:
    31,551
    Location:
    YO11 2BD
    Ratings:
    +24,580
    yes and yes.

    though the split charge from the engine isnt very efficient.
    once the engine battery is fully charged, which doesnt take long, the alternators output is reduced to simply maintain the battery, so the leisure battery charge is also reduced.

    hookup, of course, charges via the onboard charger.
     
  3. mitzimad

    mitzimad Funster

    Joined:
    Jan 28, 2008
    Messages:
    3,873
    Location:
    walthamstow east london
    Ratings:
    +5,696
    can you explain how the alternator knows which battery is full as when the split charger is operated the alternator surely sees them as one battery bank
     
    • Like it Like it x 1
  4. Ed Excel

    Ed Excel Funster

    Joined:
    Nov 27, 2012
    Messages:
    870
    Location:
    Ribble Valley
    Ratings:
    +588
    In a basic system both batteries are charged whilst the vehicle engine is running. The relay disconnects the vehicle battery to avoid discharge by leisure circuits when it's not. The relay's coil is commonly supplied from an ignition circuit, like the alternator warning light. After that you can have voltage sensing, to direct charge or solid state devices to do the lot and connect things like a fridge to the relay to operate it whilst on the move.
     
  5. cmcardle75

    cmcardle75

    Joined:
    Jun 8, 2012
    Messages:
    670
    Location:
    Reading
    Ratings:
    +264
    Typically, the manufacturer uses thin, high resistance cable between the two, with a cheap high resistance split charge relay, that results in the engine battery charging much more quickly and the alternator sensing that battery's state. Occasionally, the batteries are adjacent and have decent cable and relay, but you'll have probably fitted that yourself.

    Another alternative is to fit a proper dc to dc battery charger, which will charge the leisure battery properly.
     
  6. pappajohn

    pappajohn Funster Life Member

    Joined:
    Aug 26, 2007
    Messages:
    31,551
    Location:
    YO11 2BD
    Ratings:
    +24,580
    thanks, you put that much better than i could.
    i started to reply a while ago but couldnt find the words to explain what i meant.
     
    • Like it Like it x 1
  7. Ed Excel

    Ed Excel Funster

    Joined:
    Nov 27, 2012
    Messages:
    870
    Location:
    Ribble Valley
    Ratings:
    +588
    And if you have fitted the relay yourself, with decent sized cables, you'll probably boil your leisure battery. The circuit needs some resistance to avoid 'high' voltages across the leisure battery. 14.4V on a deeply discharged leisure battery won't do it any good but it shouldn't harm a lightly discharged vehicle battery.

    I agree, B2B charging is the better option and, of course, can be added to a 'van with an existing split charge installation.
     
  8. Wildman

    Wildman

    Joined:
    May 30, 2008
    Messages:
    15,458
    Location:
    Ilfracombe, Devon
    Ratings:
    +8,647
    Hi and welcome to the forum. The answer to your question is not very well and quite possibly.
    The split charge arrangement will never fully charge the leisure battery unless you have a battery master fitted for reasons given below.
    When on mains hookup the leisure battery will charge properly provided the onboard charger is
    a) working,
    b) switched on and
    c) switched to the hab battery.
    solar is so much simpler for most of the year.:thumb:
     
  9. cmcardle75

    cmcardle75

    Joined:
    Jun 8, 2012
    Messages:
    670
    Location:
    Reading
    Ratings:
    +264
    Yes, best to stick clear of a split charge relay if you are using a sealed battery that can't take a decent charge rate. A B2B charger will have proper microelectronics to moderate it to a suitable value.
     
Loading...

Share This Page