Installing a second battery.

Discussion in 'Tech/Mech General' started by peterc10, Jan 6, 2016.

  1. peterc10

    peterc10 Funster

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    When I bought my new Hymer the dealer fitted it with a second battery at my request. He just linked them in parallel with all the positive and negative connections going to the one battery. I did not query this at the time because that is how I wired up my two batteries in my previous motorhome and it seemed to work fine.

    I have just read the Hymer Manual (I know ..... what a wooze) and they say that all the positive connections should be on one battery and all the negative connections should be on the other one. Is that correct?

    They have also left the connections uncovered, which is OK on the original battery which is tucked away, but the new battery is more exposed. I was thinking of replacing the connectors with those plastic covered ones that you press down on to tighten to the battery post. Are these OK, given that I will be running a 2000W inverter occasionally?

    Many thanks for all the advice you can give (as long as it is sensible @Dawn B and @DuxDeluxe )
     
  2. pappajohn

    pappajohn Funster Life Member

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    Your manual is correct but its not necessary.

    Connect pos to pos, neg to neg but take the live feed from one battery and the neg feed from the other.
    It is still 12v but evens out the load on both batteties.

    Works best for large battery banks.....4 or more..... but makes little difference for just two batteries.
     
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  3. Reallyretired

    Reallyretired Funster

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    As long as the cables joining the two batteries are thick enough, and if you're potentially drawing 200A they need to be thick, the way you have them wired is fine. Mine are wired like this and I'm sure many others are also. Make sure any terminals you fit are up to the job of carrying the current.
     
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  4. peterc10

    peterc10 Funster

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    The cables they have fitted are thin and they have fitted a 20A fuse in the positive connection. But then I never told them I would be fitting an inverter! So I know either way I have to replace the connecting leads with 25mm stuff, it is just whether I should just replace like with like, or switch one of the sets of connection leads (+ or -) to the other battery.
     
  5. pappajohn

    pappajohn Funster Life Member

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    If you intend running a largish inverter I would rewire it as it is....pos one battery and neg the other.
    I didnt realise an inverter was involved.
     
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  6. Lenny HB

    Lenny HB Funster

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    As you are going to be drawing high current forget about the quick release battery terminals, they are made of lightweight pressed steel.
     
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  7. peterc10

    peterc10 Funster

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    Thanks Lenny. Some I have seen say they can take up to 800A, which is less than a quarter of what I will be putting through it. Is that just b******t?
     
  8. Lenny HB

    Lenny HB Funster

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    100%.
     
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  9. mitzimad

    mitzimad Funster

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    i was going to say we had snap down connectors and they were a pain for falling of
     
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  10. Dawn B

    Dawn B Funster

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    I was sorry to hear about your accident :whistle:
     
  11. peterc10

    peterc10 Funster

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    But on the other hand on my previous motorhome I used them and the same inverter for over a year without any problem.
     
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