Mains adaptor for 12 volt fridge

Discussion in 'Motorhome Chat' started by Dorwyn, Oct 6, 2015.

  1. Dorwyn

    Dorwyn Funster

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  2. John Laidler

    John Laidler Funster

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    If you are on EHU dos it not work on 12 volts? I have a compressor cool box which I have a mains adaptor for but that is only so I can use it in the house. In the MH it runs on 12 volts all the time.
     
  3. Jaws

    Jaws Funster Life Member

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    If your unit is drawing 5 amps constant I would look for a PSU able to handle at least 8 amps to be even slightly on the safe side .
    Those switch mode PSU's are actually ( usually ) rated at 4 amps with 6 amp surge

    Personally I would not bother at all.

    If you are on hook up, then the van charger will be the thing supplying the amperage ( when you think about it ) so why double up ?
    The only time you would need a mains supply for it is if you remove it completely from the van and away from the 12v supply
     
  4. Jaws

    Jaws Funster Life Member

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    Sorry DBK.. we both posted at the same time !
     
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  5. Dorwyn

    Dorwyn Funster

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    The reason I was thinking of doing that is to reduce the load on the battery.
    When I'm on EHU it doesn't last more than a couple of days before it starts to struggle. I do occasionally use a battery charger but cannot use the one I have on permanently, since once it is charged fully, the charger switches off, and has to be manually restarted.
    While I'm paying for electric I thought I could use it to run the fridge.
    I recently changed the battery configuration from 2x 110amps to one 130amp, for reasons of storage space. I do not have a van charger as such.
    Regarding the amperage the fridge uses, I am not sure what it does run at, it's only a small 70 litre fridge, but I do not have the manual to check the spec.
    Anyway, it was just an idea, which seems to have been shot down.
     
  6. Jaws

    Jaws Funster Life Member

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    There is something very wrong with your charger in that case !
    I would address the problem rather than do a work around to be honest ....

    If it all worked correctly you would still be using more or less the same amount of electric .. The charger is really only a semi-intelligent power supply anyway...
     
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  7. scotjimland

    scotjimland Funster Life Member

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  8. Dorwyn

    Dorwyn Funster

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    I do not have an on-board Zig or similar system. There is nothing wrong with the charger, it is designed to need a reset. Another make charger would be an obvious choice, but they are so expensive. Since there is a connection for a mains power pack, I was thinking of using that. After all, the 3-way systems can do that.
     
  9. Dorwyn

    Dorwyn Funster

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    ... although the Sargeant model does seem good value for a 25 amp unit
     
  10. John Laidler

    John Laidler Funster

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    No one is shooting down your idea now we understand the reason for asking but I think in the long term it will be better to sort out the on-board charging. One reason is if you can't charge the battery when on EHU it is going to be repeatedly run down and I don't think that is good for it, better to keep it topped up continually.

    As for current, my Dometic compressor cool box uses 5 amps when it is running, which in typical UK temperatures is for about 5 minutes then it shuts down for about half an hour or so before starting up again when it has warmed up a bit inside so I suspect your 5 amps estimate is about right but it is probably a bit more than that momentarily when the motor kicks in.

    Sad person that I am I logged the temperature changes with a Raspberry Pi over a twelve hour period after I got it so I could work out the best setting for keeping the beer and wine cool. Note how it fluctuates quite a lot to begin with including several excursions into the negative zone before levelling off around 4C. This was with it empty and I suspect the temperature fluctuations will be much slower when it is full - but I haven't tried that yet.

    upload_2015-10-6_14-11-19.png
     
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