How to fit solar panel to 2nd battery

Discussion in 'How To' started by keith walker, Jul 8, 2009.

  1. keith walker

    keith walker Read Only Funster

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    hi.
    Can you help,still new to this game, just had a solar panel fitted & would like to fit a 2nd battery, same size, no idea what cable to use or how to fit it. Any ideas?

    Thanks
    Keith
     
  2. oldun

    oldun Read Only Funster

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    As solar panels on offer vary from about 1 W to 120 W the size of the cable will depend upon the current delivered by the panel and the length of the run.

    To give an answer we must know the maximum current from the panel and the length of the cable.
     
  3. keith walker

    keith walker Read Only Funster

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    Solar panel to battery?

    Thanks for the information.

    The solar panel is 85w & the distance from 1st to 2nd battery is approx 1mtr.
    The batteries will be 210amp when combined.

    Regards
    Keith
     
  4. hilldweller

    hilldweller Funster Life Member

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    Are you sure about this, I think he wants to fit a second battery, nothing to do with solar.

    And the answer to that is that look at the original battery cable and fuse both ends of the positive line.
     
  5. pappajohn

    pappajohn Funster Life Member

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    in answer to HOW to fit it.....

    link new wires between pos(+ ) to pos(+ ) and neg( - ) to neg( - ) of both batteries. you'll know if you get them the wrong way round:Eeek:
    put i fuse in both ends of the pos( + ) wire as close to the batteries as possible
    i use 35amp blade fuses and enclosed fuse carriers from a motoring shop.
    if a fuse should pop then a spark may ignite any gas from the battery. unlikely but possible.
    the batteries should have a vent tube fitted and this should go through the floor to the underneath of the van.
     
  6. Road Runner

    Road Runner Read Only Funster

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    How do you get to 210 amps? is it 2 x 105 amps?
     
  7. keith walker

    keith walker Read Only Funster

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    hi john
    yes 2x105 amps.the 1st battery is already fitted

    keith
     
  8. Frankia

    Frankia Read Only Funster

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    I note that the batteries are to be about 1m apart - are they going into under cab seat boxes?
    I f they are be carefull about running the cables through holes in the metal boxes. Make sure that the cable is well sheathed and they pass through a gromet to prevent chaffing.

    To give the least loss due to cable length / thickness I use jump start cables between my batteries (3 of them) even though they are co located. The cables are fused and terminate in the quick release type battery clamps in order to facilitate easy servicing / replacement where necessary.
     
  9. keith walker

    keith walker Read Only Funster

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    Thanks bernie
    good idea.keith
     
  10. pappajohn

    pappajohn Funster Life Member

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    while this is good advise i personaly cant see the need for such heavy cables.
    maybe if one battery is under the seat, another midway in the van and the other is in a rear locker then, yes.
    my main/original battery is under the passenger seat and the second is under the dinnete seat just behind the drivers...around 1 mtr away and i use 7mmsq which i believe is 50amp cable but fused at 35amp.(havent blown a fuse yet)

    the wire feeding the control panel /lights/ waterpump/ 12v sockets from the batteries is only around 2.5mmsq or 4mmsq which has a run of around 5mtrs and feeds the entire van.

    jumper cables are usually 16mmsq or 25mmsq which seems a bit big for what its doing considering the starter motor draws maybe 400/500amps from the engine battery and that uses 25mmsq cable.

    just out of interest...what size fuses do you use......

    just my opinion:thumb:
     
    Last edited: Jul 8, 2009
  11. Douglas

    Douglas Read Only Funster

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    I think you are missing the point, in this case its not about carrying amps but reducing the drop in voltage.

    Doug...
     
  12. oldun

    oldun Read Only Funster

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    I see that no but have you read the title?

    "How to fit solar panel to 2nd battery! ??????????

    There are too many posts with stupid titles - such as "newbie need help" or "Got some problems here"

    However I accept that primarily I am at fault because I did not fully read the post, only the title. So I will stand in the naughty corner for 2 hours.
     
  13. hilldweller

    hilldweller Funster Life Member

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    It's standard practice. Don't worry about it.

    More important are you being plied with wine ? Lots of wine.
     
  14. Frankia

    Frankia Read Only Funster

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    Sorry I didn't answer earlier as we have been away in the 'van with no internet.

    Yes that is the reason - reduced loss. It makes sure that all batteries are charged equally and when in use basically behave as one big battery no matter what the load.

    I have often found that 'van converters don't have auto electricians working for them and will look at a set of instructions which came with the charging unit which will say use xx cable to connect to a battery within 1 meter. They then put the cgarger at one end of the 'van and the batteries at the other and use the same cable. 1 'van we bought had this set up and between the charger and the battery it lost 2 volts and the cable got rather warm. I have even seen a 'van with a 30amp fuse at the battery and the cable going from it to the control unit fusues rated at 8amp.

    Moral - go for overkill in cable size and fuses as 12v can be more dangerous than 240v as it is generally used at higher amperages therefore the risk of fire is often much higher.
     
    Last edited: Jul 11, 2009
  15. The Wild Ones

    The Wild Ones Read Only Funster

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    Bernie is bang on the nail here! More fuse protection and at the correct ratings is the way to go. Oversizing a fuse can be as dangerous as no fuse at all. One thing to bear in mind is an appliance under a fault condition. It can and often will draw a lot more current than in normal operation even if a short circuit does not occur. Even appliances with built in short protection should be fused imho.
     
    Last edited: Jul 12, 2009
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