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Adding a 2nd battery to 3rd Gen for starting

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  • Adding a 2nd battery to 3rd Gen for starting

    Hi all,

    After a recent flat battery (old battery I'm guessing as alt seems fine) I decided that I would add a 2nd battery.

    I have an unusual 3.0 TD 3rd Gen Surf which has just one large (800CCA) battery on the driver's side (instead of the usual 2 smaller batts, like i had in my other Surf)

    There is an empty space on the passenger side of the engine bay, where a battery could fit, so I'm planning to install a 2nd identical battery there and connect it in parallel to operate as an additional reserve for cold starts etc.

    After a bit of Googling I found that most of the tutorials and other advice were for people who wanted a leisure battery and would be using a deep cycle battery for the 2nd battery, and using a lot of power with the engine off. I don't need any of that, I only want the 2nd battery for absolutely reliable starting. It's probably overkill, but this is literally the ONLY thing that's ever gone wrong with either of my Surfs over the past 10 years, and so I want to prevent it ever happening again!

    My question is: If I simply connect the two batteries in parallel, is there any danger of damage to things like the starter motor, from the increased available current? (from my limited understand of electronics everything should still draw the same current it did before as the system's voltage will still be 12V, but I wanted to check)

    I'm planning to use heavy 16mm2 110A cable for both connections.

    Any thoughts?


  • #2
    No it wont damage anything

    However, make sure the batteries are a paid and identical. Id suggest purchasing an identical set. As if one battery is better than the other, the bad battery will drag it down and itll have a shorter life.

    The other option would be, if it is not happening that often and you want it just for starting, is fit a cranking battery, which has hi output for shorter time (cranking!) and have it only connected when you need the extra power

    Id suggest optiok one being the best, though.