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Why dual batteries

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  • Why dual batteries

    I am being made redundant and the wife says lets buy a fortuner !

    So I am new to the world of dual batteries. Why/do would I need dual batteries?

  • #2
    Hi Two89w and welcome to the forum!

    Your wife has the best attitude ever!

    The main reason to get a dual battery system is to run your extra devices when out camping. So for example, if you had a fridge or extra lighting you could run it off the second battery overnight which could be isolated out from your main battery, depending on how you have set it up. This gives you a fresh battery to start up in the morning instead of a flat one which could range from annoying to life threatening depending on where you are...

    Again various levels of complexity with those as well
    Fortuner Forum Default Signature!


    • #3
      Yup, What Shaun said. Depending on the setup, the second battery can be of a different design eg a deep cycle. These are designed to provide a smaller amount of power but for a longer time, where a normal crank batttery does large amounts for short time. Deep cycles can also be discharged by a greater amount than normal batteries. It all comes down to what you want from the car. If you plan on camping/touring with fridges and want to be self sufficient, run a 2nd battery, possibly with a solar panel so you can be charging while not driving. If you are planning to be travelling to places with power then its not worth the hassle.

      Getting a second battery (N70 size) in the Fortuner is a tight squeeze, lots of wiggling to get it in and out. Cost wise, your looking at $200+ for a battery, $150+ for a brand name battery tray, then anywhere from $300+ for a dc-dc charger. These cars have the new "smart alternator" so running a run of the mill dual battery kit wont charge the second battery correctly. Then if you are thinking solar, add another $150 or so for a panel, all this is parts only, still have to add the cost of wiring, connectors, auto electrician rates etc

      But spending a week in the wilderness, running fridges and/or a freezer and being totally self sufficient is pretty good


      • #4
        Apart from lighting and the fridge when camping I also use the fridge in the back during summer if I am out shopping on a Sat morning and need to keep food cold.

        I have also used it to power a 12V fan when it is really hot and there is no breeze getting into the tent.


        • #5
          Anyone had experience with running a Waeco/Engel or similar battery pack with a fridge as an alternative to the second battery system?

          For example could you run the fridge directly from the battery pack but plug in the battery pack to the 12v socket in the rear so the fridge is always running but the battery pack re-charges when the engine is running? I am wondering much you would need to drive each day to keep the battery pack charged up enough. Perhaps so much driving it is not feasible.

          I understand not as good as getting the proper dual battery fitted but interested in what people's experiences have been with such battery packs.
          Crusade, Summit Bar, Dobinsons Monotube, BFG AT.


          • #6
            Have a look at the battery packs. Im sure they are only 36ish Ah. Pretty small batteries for the price. Also be aware the cig lighter 12v sockets are unreliable, often fall out and ive melted many plugs just running fridges. The lighter socket would be 10amp max, so if the battery charges at 10A your looking at a couple of hours to charge from flat. (20% remaining is classified as flat for deep cycle, so your 36Ah battery will only give you 28ish AH before flat)

            The Waeco CFX50 fridge draws just under 1Ah, so in theory you would get 24 hours out of a battery. Then probably 2-3 hours of charging to get back to full charge.

            The Waeco battery pack is $330 for 36Ah, a 100Ah deep cycle battery is $200 and for the extra $130 you could buy a charger for it, thus giving you close to 80 hours before needing a recharge. but they are also heavy (hence why they are mounted as a second battery)

            It comes down to personal choice, for the money it would probably be worth looking at mounting a second battery. At least then you can find a charger with solar input and have a panel to keep things charging if you are camped for a few days. Just depends what you want to do with it.

            Finally, i dont know if you have a fridge, but if you get one with built in 240v and 12v then at camp sites just hook it up to the mains and not waste the battery

            Last edited by deeman111; 16-05-2016, 02:20 PM.


            • #7
              For the last few years on my previous vehicle (Suzuki XL7) I ran a single battery. I replaced the original battery with the biggest that would fit in the normal tray (an N70). I also chose a "hybrid" battery (a Supercharge All-Rounder) which is suitable for starting and cycling. The battery was rated at 105Ah. For longevity, and since its not a dedicated deep-cycle, I chose to only discharge to approx 50%, i.e. 50Ah. My 40L engel uses approx 1Ah/h during hot weather (less in cooler weather). As such this setup gave me around 50hrs before needing to run the car. This was good enough for a 3-night camp without any driving. Any longer than that and I'm usually driving somewhere anyway. When the car is running, the battery is charging at full rate (as high as 80A or so), take a short drive and you are back to full again. This setup suited me fine.

              Of course, it is not as safe as an isolated dual-battery setup. I had a manual petrol car (easy to push start), carried jumper leads, and always travelled with others, so a flat battery would not be a disaster (though it never happened).

              For the new Fortuner I'm still considering my options, but I may take the same path again, though this time I will employ a low-voltage cut-off between the battery and fridge (I don't run any other accessories) just in case. It looks like an N70 will fit in the primary battery tray. Given that this has worked so well for me for the last few years, its hard to justify the expense of a dual-battery setup, for my camping style anyway.



              • #8
                Going off super cheap auto prices

                Century MP620 marine battery (good for cranking and deep cycle 75Ah) $219
                Ridge Ryder DC-DC 20A charger - $169
                SCA large battery tray (requires some basic modifications to fit) - $24.99
                SCA battery clamp - $14.98
                Miscellaneous wiring and bolts - $50

                Total of $477 for a complete dual battery setup. So for $150 more than the waeco setup you get double the power, a hardwired system that wont fail (compared to plug falling out of 12v socket or overloading system)

                Obviously this is a cheap setup, but it will work. I have the same battery tray and clamps in my fortuner, a bigger marine battery (100ah, got it on sale at BCF for $200) and a CTEK dc-dc charger ($300ish). Ive also run a large gauge wire to the rear of the car with an anderson plug on it, so i can run 2 fridges when camping plus anything else.

                In the end, whatever setup works for you is great as long as you get out and see this great country we live in!!