12v wiring help

Discussion in 'Tech/Mech General' started by ehuplad, Aug 15, 2013.

  1. ehuplad

    ehuplad Read Only Funster

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    Looking to fit a CTEK d250s battery to battery charger, I have to run a cable from the engine battery to the leisure bat were it will be mounted.

    Not easy to do this under the twin floor, there is already a cable that puts 1.5 amps into leisure bat with engine running it looks like it goes into main board bat charger.

    The question I have, is can I just use this, it goes through a fuse near the charger, I would disconnect on the outlet of this fuse and run directly to d250s.
    What could this feed in the board, or charger or is it just for the battery?

    Any test I should do on this wire.
     
  2. rainbow chasers

    rainbow chasers Read Only Funster

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    What are you attempting to do? Replace the on board charger, or have an additional charger that will charge both batteries, assuming yours only charges the engine whilst running?

    I think your ideal would be to replace the onboard charger, as having two may confuse matters - or over complicate the management.

    Ill look into it tomorrow - off home now, getting late and my eyes are hanging out!:thumb:
     
  3. motorhomelover

    motorhomelover

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    A word of warning

    A Little Knowledge can be very dangerous !!!!

    Don't risk your motorhome going up in smoke as it very likely will
    When messing with the very high amperage found in12 volt systems
    Pay an Auto electrician. Get a warranty and sleep safe in your pride and joy

    Cut wires use existing wiring for some thing else and your asking for trouble
    :Doh:
     
  4. ehuplad

    ehuplad Read Only Funster

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    Fitting a battery to battery charger, it takes its feed from the engine battery.

    My current set up charges the leisure battery from the alternator but at only around 1.5 amps. this new charger is only for when the engine is running existing charger used on hook up.
    The current set up already has a live and earth I believe from the engine battery, this is what is fused and then goes into charger board. my thinking is that this wire is just used to put charge into the leisure battery with engine running (although only a trickle) and also charge the engine battery from the charger on hook up.
    My thinking is this wire could be used instead of running more live and earth wires to do the same job.
    The only issue I can see is that I would not have the engine battery charged from the leisure battery charger on hook up, unless, would a relay allow this

    Or am I missing something??
     
    Last edited: Aug 16, 2013
  5. robnchris

    robnchris Funster

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    Have a look at the Eddie Vanbitz Battery Master perfect for keeping both batteries topped up.:thumb:


     
  6. wivvy's dad

    wivvy's dad Read Only Funster

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    What he said.....
     
  7. ehuplad

    ehuplad Read Only Funster

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    I may have misled you on the earlier post, I am not looking to have a battery master as this does not do what I require, it is the leisure battery I need to be charged from the alternator, Just looking for advice on wiring the ctek d250s.

    Looks like I will have to run 2 more wires from the engine battery to feed this charger.
     
  8. pappajohn

    pappajohn Funster Life Member

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    this charger is presumably capable of a 25 amp charge current.

    if so you need 4mmsq cable as a minimum depending on length.
     
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  9. pablomc

    pablomc Funster Life Member

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    I reused the cables from my engine battery to leisure for my B2B as I too have a double floor. Ideally the thicker the better. Mine is 16mm2 and it works fine although I would have preferred 25mm2. Make sure to include a suitably sized fuse at each end.
     
  10. JeanLuc

    JeanLuc Funster

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    Having read earlier advice and your responses, I would be tempted to consult a motorhome electrician. A couple of thoughts.
    Firstly, you say that the alternator only puts 1.5 amps into the leisure battery; this seems very low from my experience. At what battery condition are you measuring this current? If it is when the batteries are almost fully charged, then a low input current may be seen. If they are well discharged, it should be much higher. For example, when the batteries are low, and the engine is running, the needle on my control panel indicates maximum, i.e. 30 amps or more.
    Secondly, you may need to take account of the type of charging system already installed when deciding on a B2B charger. A Schaudt Electroblok for example does not always work easily with a B2B unit and an alternative monitoring system may be required. Recently I noticed Eddie Vanbitz stated that they recommend fitting a Victron monitor when a B2B unit is installed with the Schaudt system. I realise that Hobby may use a different system but it is worth checking compatibility anyway.

    Attached is a cable sizing chart from Sterling Power Products in case you decide to proceed.
     

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  11. ehuplad

    ehuplad Read Only Funster

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    Was yours a sterling ??

    Mine only puts a max of 20amps into battery I am using 6mm2 cable as per the recommendation of CTEK.
     
  12. ehuplad

    ehuplad Read Only Funster

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    Was yours a sterling ??

    Mine only puts a max of 20amps into battery I will be using 6mm2 cable as per the recommendation of CTEK. may be 2m run. I have not checked the size of the existing cables will look at them tomorrow.
     
  13. ehuplad

    ehuplad Read Only Funster

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    according to the fitting instructions it is not rocket science.

    Positive cable from engine battery suitably fused at each end, attached to positive connection on B2B, earth from b2b to earth point on vehicle, positive cable from b2b to leisure battery suitable fused, with the correct sized wiring.

    Why would this need to be fitted by a auto electrician ??
     
  14. pablomc

    pablomc Funster Life Member

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    Yes mine is the sterling.
     
  15. Whatton

    Whatton Read Only Funster

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    Maybe I'm being a bit thick here but why is there a requirement to put a fuse at either end of the cable?
     
  16. ehuplad

    ehuplad Read Only Funster

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    Because the engine battery wire can be live from both ends, this b2b also charges the engine battery from a solar panel, solar not discussed yet as that will be done next year.
    So the cable could be live at both ends.
     
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