Fitting A Split Charge Relay?

Discussion in 'Motorhome Chat' started by Yorick, Sep 8, 2014.

  1. Yorick

    Yorick Funster

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    I've decided to get one of these but folk seem to want lots of dosh to fit them.

    Are they easy to fit? I know naff about leccy but do have common sense and can follow instructions.

    Or best to pay a pro?

    And could anybody recommend a suitable one from eBay please?

    Cheers
     
  2. Yorick

    Yorick Funster

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    And also the fridge is wired directly to the van battery at the mo as per the instructions in handbook.

    would a split charger somehow be fitted so that the fridge won't draw a charge when the engine is not running?
     
  3. TheBig1

    TheBig1 Funster Life Member

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    it really is very simple to fit a split charge relay. even easier is to fit a smart relay as it needs less wires

    one fused thick wire from the positive terminal of the van battery to the relay
    one wire from the negative of the van battery to the relay
    one thick wire from the relay to the leisure battery
    one thick wire from the relay to the fridge
    using a smart relay, it will detect the voltage at the van battery and switch on when the alternator is charging. otherwise you need to find an ignition triggered live circuit

    probably about an hour or so work and parts about £30 with smart relay
    http://www.ebay.co.uk/itm/RYDER-Sup...arts_Vehicles_CarParts_SM&hash=item19dd6a6a33
     
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  4. timdownieuk

    timdownieuk Funster

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    Which fridge? Which handbook? That sounds like bizarre advice guaranteed to flatten your battery should you forget to manually turn the 12 V supply to the fridge off.
     
  5. Yorick

    Yorick Funster

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    It's a Dometic fridge and manual says so. That's why I wanna sort it all out.
     
  6. Badknee

    Badknee Funster

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    Don't like the sound of that, starter battery or leisure battery?
     
  7. Yorick

    Yorick Funster

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    Starter battery
     
  8. Badknee

    Badknee Funster

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    No, no, no, it's bad enough flattening the leisure battery but a nightmare to flatten the starter battery ..................... push anyone?
     
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  9. timdownieuk

    timdownieuk Funster

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    Model number?

    Dometic do an awful lot of fridges.
     
  10. TheCaller

    TheCaller Funster

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    It should say 'directly to the starter battery, via a relay'. Directly, as in - separate wiring, not shared with anything else. But it must go via a relay, so that it only runs while the engine is running. The relay senses the rise in voltage that occurs when the alternator starts charging, then makes the connection to the fridge.

    This is a separate relay to the split charge relay which controls the charging of the leisure battery (at least, it should be). Having said that, combination units are available.

    Simple split-charge systems are ok for leisure battery charging if you don't need to rely on the leisure battery for much or for very long. If you need more from your batteries, then add solar panels if you stay in one place for a while, or a battery-to-battery charger if you drive about quite frequently - or both, but now we are talking serious dosh.

    I would get a pro to fit either relay. It's not that they are difficult, but if electrics is all a black art, then you are missing the knowledge to spot some minor issue that could cause quite a serious problem. A basic split-charge system won't take long to do unless the wiring runs are complicated.

    Put the bike in the van, take a day or two off, make a trip out of it & go to the Severn Gorge Park site in Telford. Dave Newell is just over the road - Jackie will even make the campsite booking for you. You & Dave are both into motorsport, except he has two more wheels on his wagon. With the bike for transport, there is plenty to see in the area while he puts in whatever you need. Most importantly, he'll tell you what you really need, which might not be what you first thought.

    P.S. All this assumes that the fridge is a three way absorption fridge - runs on gas, 12v or mains. Direct to the leisure battery would make sense if it's a compressor fridge.
     
  11. scotjimland

    scotjimland Funster Life Member

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    yes, but they all work with the same principal.. they all need TWO 12v supplies, one from each battery.

    1. 12v A Permanent supply from the leisure battery to power the electronics. ( whether on LPG, Mains or 12vdc )

    2. 12v supply from the engine battery that is only switched on when the engine is running . This is done via a relay ( so called split charge relay) operated by the voltage from the alternator when the engine starts.. The same relay (provided it has 2 sets of contacts) is also be used to charge the leisure battery.
     
  12. eddievanbitz

    eddievanbitz Trader - Funster

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    Right! two relays, one for the leisure battery and one for the fridge. You can use Voltage Sensing Relays (VSR) and they will automatically "close" (start to work) when the engine is started and the engine battery voltage reaches a certain voltage. When the engine is turned off the voltage will drop and this will cause the relay to open "stop working"

    This means that no power will be taken from the engine battery from the fridge or the leisure battery.

    The down side of VSR's is that they can play up if you have a solar panel connected to the engine battery as this can cause the VSR to "think" that the engine is running.

    It could be better in such cases to connect the alternator to the relay conventionally. It takes longer, and will cost you more (if having it fitted) but will be more reliable in the long run

    I PM'd you about your chassis

    Eddie
     
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  13. rangitira

    rangitira Funster

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    Yes! Many thanks Badknee, you have just solved one of my Problems with the master battery losing charge:clap2::notworthy2:
    May your Camels have a thousand babies and may your enemies have a thousand Fleas!:notworthy2::notworthy2:
     
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  14. mitzimad

    mitzimad Funster

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    one method is to use a smartcom relay to switch the split charge relay the advantage is you get the correct supply for tyhe fridge
    cable size is important as you dont want to be loosing current along the wires
    http://sbmcc.co.uk/forum/index.php?app=gallery&album=607 not sure if you will be able to see this diagram if not pm me ill try another method
     
  15. Yorick

    Yorick Funster

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    Hmm, that's got me worried. I'm fitting a 150w panel and it makes sense that a split charge relay could be confused. But what problems could occur ?

    Does anybody else have a solar panel and SCR fitted ?

    Cheers



    My mate is fitting it all and he is a whizz with electrics so just need to tell him what to do
     
  16. eddievanbitz

    eddievanbitz Trader - Funster

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    split charge diagram.jpg
     
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  17. Yorick

    Yorick Funster

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  18. Badknee

    Badknee Funster

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  19. pappajohn

    pappajohn Funster Life Member

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  20. Sheddy

    Sheddy Funster

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