Fridge and battery/solar panel size

Dieseldragon Feb 8, 2017

  1. Dieseldragon

    Dieseldragon Member

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    In anticipation of a 74l fridge that I am planning on buying, I need to think about powering it. I have a short wheel base 90, with a roof tent.

    The fridge draws max 5A, so I am trying to work out what I need to power it.

    I'm thinking that a 100Ah battery with 100w solar panel should be enough. I think I would prefer it to be a stand alone setup.

    Are there any guidelines to ensure that my beer never becomes warm?
     
  2. MarkW

    MarkW Well-Known Member I am in morocco

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    74l ! that's a lot of beer :)
     
  3. ByronJ

    ByronJ Well-Known Member I am in wales

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    If your fridge compressor ran constantly it would draw 120 amps a day. That is a lot of power. Effective insulation is the key to reducing power consumption. Every time you double the insulation you halve the power consumed. Insulation is dirt cheap but it takes up space. As your fridge is likely to be air cooled then also ensure there is good airflow across its vents.

    The large fridge on my boat has 200mm of specialist insulation foam and consumes around 30A on a hot day in Greece. My solar panels easily cover this.

    The freezer in my car sits in a custom built plywood box with around 40mm of insulation. Doing that reduced its power consumption by 25% in 20C ambient. I shall have a better idea of its actual consumption when I use it on the western Sahara Trip in April.
     
    Last edited: Feb 9, 2017
  4. Dieseldragon

    Dieseldragon Member

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  5. Andykdj95

    Andykdj95 Active Member I am in great_britain

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  6. nick_the_fish

    nick_the_fish Well-Known Member I am in great_britain

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    Out of interest why would you prefer it to be a stand alone set-up? Why not hook it up to the main battery/ leisure battery? Are you going to be stopped for a very long time inbetween driving?
     
  7. SteveS

    SteveS Well-Known Member

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    Some thoughts on my overland experience running a fridge/battery long term. My 50L Waeco c/w insulating cover draws 5.3A and at 40C is running 55% of the time. I found that having only a single 100Ah leisure battery under those conditions even with an 80W panel is just not sufficient to power a fridge from dusk to dawn. Using round numbers you will have 14+ hours of no solar input (probably more) so 14 x 5.3 at say 30% duty (cooler at night) will consume at least 22Ah.....and that assumes your one battery is fully charged. a 100Ah battery will be at least 22% discharged in the morning even if you exclude other power drains like pumps, chargers, lighting etc. It could easily be 30% discharged. This is not a function of the amount of panel watts - you can only fully charge the battery - it is a function of the battery capacity. We constantly discharged our 100Ah like that and knackered it pretty quickly. This year we will be on 2x 100Ah and we have upped our panels from 80W to 180W. Your 100W panel is only just delivering 8A in full sun - fridge will take 5.3A x 55% average, so 3A leaving only 5A to top up the batteries, power other circuits etc.....if it is not full sun or you are in shade etc then you may not get any net top up charge at all. I can run both my panels off the truck so that I can park in shade to keep it cool and yet put the panels in the sun and optimise their angle to it. I use an IBS split charge controller and the fridge has a low voltage switch off. Temperature management is vitally important - e.g. keeping the truck ventilated when parked up, re-stocking the fridge with cold beers or cooled from a river or cool night temperatures. If you plan to travel in the UK and for weekends only then you may get away with a single battery
     
  8. ByronJ

    ByronJ Well-Known Member I am in wales

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    The practical advice above from @SteveS is very helpful and has highlighted how vital battery selection is. A standard start battery will probably be knackered after a few dozen discharges to 50% whereas a specialist deep cycle battery from someone like Lifeline will be good for over a 1,000 cycles of 50% discharge. However if you use a deep cycle battery to start your engine you will destroy the battery in seconds. The Lifeline batteries on my boat are now 6 years old and still going strong.

    In my 80 I have installed an Odyssey PC1750 75Ah (C20 rating). It is rated to handle 400 discharge / charge cycles of 80% of its C10 capacity (65Ah), giving 52Ah (and leaving the battery with 20% capacity remaining). Most 100w batteries should only be discharged to 50% of their C20 rating i.e. 50Ah.

    The Odyssey PC1750 also delivers CCA of 950A so it is very happy to start my engine should my start battery fail (my 80 is 12v start). I think the Odyssey Extreme range are superb batteries.

    Incidentally most 100w 12v solar panels will deliver a maximum current of less than 6A. This is because they need to deliver a voltage of 13.8v or more to actually charge a battery. The most I have seen from my 100w panels is 5A. Check the specifications of the panel you intend to buy, looking particularly at its rated maximum current output. The 100w maximum rating is calculated using the maximum voltage the panel can produce which is often around 18v so the maximum current it can supply is 100/18 which is significantly less than you get by dividing 100 / 12.
     
    Last edited: Feb 25, 2017
    thelal likes this.
  9. SteveS

    SteveS Well-Known Member

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    I thoroughly rate the Odyssey's too - if it wasn't for the fact that I would have to refit at least two if not 3 batteries then I'd have done it - but it was just too costly. Best not to mix and match the AGM with LA batteries. The Odyssey's I took to arctic Norway at -40C and Sahara at +40c and they were brilliant. The PC1750s do fit a 100 and are available in standard and reversed pole layout. Lithium is the new boy on the block and could be worth a look too
     
  10. SteveS

    SteveS Well-Known Member

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    Do you mean 80% discharged or 20% discharged leaving 80% capacity?
     
  11. ByronJ

    ByronJ Well-Known Member I am in wales

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    Drats! I did not know the PC1750s were available in reverse pole layout. That would have saved me some fitting trouble.
     
  12. ByronJ

    ByronJ Well-Known Member I am in wales

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    Sorry I was not very clear 80% Depth of Discharge so leaving 20% capacity.
     
  13. SteveS

    SteveS Well-Known Member

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    Sorry - my mistake - it is the 2150s that have a mirror image pair and you can get two of those in a 100. So you did not waste your time after all!
     
    ByronJ likes this.
  14. Cistec

    Cistec New Member I am in australia

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    This is a very simple break down of how to figure out usage of power to requirements. I assume, to really know your needs you really have to over compensate when guessing what you need just to be sure you are covered when going out the first time just like the newbie travellers like me who are only just working all this power thing and where cables go? So articles like this with replies like yours really make sense when you realise you are talking to very high proportion of non tech members who want to be taken by the hand and maybe little diagrams to help and taking complex setups and tech jargon and distill it down to the really basic form so all can understand it...even me. IMHO
     
  15. SteveS

    SteveS Well-Known Member

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    Yes - you have to have a little extra, but not too much as then you will be over engineering - more weight, more cost etc. The most important thing in my view is to understand what, where, when and how you intend to use your vehicle.....this will help guide your needs and thus your requirements. When we started out (as novices) we started with simple trips and over a period of time built up our repertoire and experience: Arctic winters, deserts, mud and river crossings etc. Initially 1 or 2 days but working up to weeks and then months. This allows you to understand your own and your vehicle's shortcomings....and give you time to fix the problems you encounter before you go on much longer tours. Forums like this are a valuable source of expertise - for example my Hedgehog overland build thread.
     
  16. Cistec

    Cistec New Member I am in australia

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    Cheers mate nice sound solid common sense advice ..The only problem I got is I have accepted the offer of going on a 8 week trip via Simpson Desert and Canning Stock and a few other places from the itenerey I have been given, so I am in a learn as much as I can mode and we go in about 7-8 weeks. The one good thing about this trip is the reason I accepted is because it is with very good friends and they are very experienced remote bush campers with farmer mentality (don't suffer fools gladly and say it as they see it), but my ego will not allow me to keep asking them what I am asking you because you will not be there to correct me so i will try to look as though I am at least partly competent. So when I rock up to the group they are not going to say jesus!! it feels like I already spent 8 weeks with you building your troopy. need I say more?
     
    clivehorridge likes this.
  17. SteveS

    SteveS Well-Known Member

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    @Cistec - we hope to be spending a year driving around Australia in 2018 - planning on messing about around the Simpson, Oodnadatta, Cape York, Tasmania, around the big circuit, all over really. As you'll be an expert by then I will be able to ask you for input in our prep. Will be bringing the 100 over in a container to Brisbane. Been a lot of flooding out on the Simpson in recent years - how is it at the moment? I almost took up a similar offer 2 years back to drive the Simpson - would have flown over and borrowed a truck as part of a larger group - sadly couldn't make it all fit in with work and other commitments
     
  18. Cistec

    Cistec New Member I am in australia

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    Well from what I have heard the desert has a lot of sand!! a real lot of sand!!!...but you could correct me if I am wrong. I heard it is still dry Oh! did I mention sandy as well? On a serious note we have had severe heat waves in NSW Australia reaching near 50 degrees heat 46 degree where I live, I have been told the weather over there in Simpson is HOT HOT HOT in the day and COLD COLD COLD at night. By the time you get to Australia in 2018 we should be on second trip overseas if we can survive this one, back to UK via Timor (indonesia) through Europe but since UK has dropped out of the EU visas could be a problem with our British passports so we might have to use our Australian ones ..not sure? Where are you from?
     
  19. SteveS

    SteveS Well-Known Member

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    Do a search on YouTube "simpson desert flooding". UK will still be a member of the EU for at least two years - most pundits are saying at the earliest March 2019. PM me if you want any specific info.
     
  20. SteveS

    SteveS Well-Known Member

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    Dieseldragon likes this.
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