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DC to DC charger? Do you need one?

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  • DC to DC charger? Do you need one?

    Hi all,
    After doing a lot of research on the best setup for my dual battery system I came up with the conclusion that a DC to DC charger is not required to ensure a fully charged auxiliary battery.
    DC to DC chargers are expensive and they are temperamental to the high temperatures found in the Fortuner engine bay, the last thing I want is to have to either relocate or replace a failed unit.
    Ive come from a Landrover D3 in which I had Traxide isolator fitted. I rang Tim from Traxide to discuss the Fortuner DBS and DC to DC chargers.
    After a long and in depth discussion he mentioned that he had worked with some of the guys from Pradopoint. And after much testing found that the Traxide isolator out performed the DC to DC chargers.
    Some owners had removed their DC to DC units and replaced them with the Traxide units.

    I have a winch fitted so I installed this isolator:
    Its not affected by heat.
    I have the wiring to both an Anderson plug at the rear for either a van or charging both batteries via either a charger or solar. A separate circuit for my ARB compressor and another for the Engel fridge and rear LED camp lights.

    The Anderson circuit has a 50amp auto reset circuit breaker and the other circuits are connected with a low voltage cutout unit:

    On testing I have found full voltage charge going to both batteries once the engine is started.

    The isolator has other modes such as shared mode, winch mode and jump start mode.

    I have it pared with a Optima Yellow top.

    I have no commercial affiliation with Traxide and with a 5 yr warranty on their products they are both good value and a reliable alternative to DC to DC chargers.

    Call Tim on the website phone number if you are interested in his Australian designed and made products.

    Cheers Rich

  • #2
    Hi Rich,
    Thanks for the info, quite interested as I had troubles previously with dual batteries in the front and two deep cycle in the rear of my troopy. I found that I could only reliably charge 1 battery at a time in the back and that voltage drop was the main limitation, I ran HD dual leads and a high efficiency (permanent duty) isolator solenoid (older can style) - accept that this was a dated solution by todays standards.
    My understanding of the DC/DC is they can boost the voltage substantially and that rear (
    or trailer)
    batteries would see too much voltage drop with your configuration...when you say no voltage drop are you talking the engine bay aux battery or trailer batteries?
    Good topic,

    Another thing I meant to say earlier, the DC/DC can be mounted in the rear of the vehicle or trailer, most mount in rear of vehicle so they can charge either onboard or various trailers they might have (e.g. if you have a hydraulic tipper and a camper - you can connect to DC/DC via Anderson).
    Last edited by Adam Newbury; 17-04-2018, 02:29 PM. Reason: another point added.


    • #3
      i need to differ with you here , a DCDC unit is definitely required on dual battery systems nowadays.

      As you found , full voltage will be going to both batteries once the engine is started , BUT - the ECU controlled alternators will quickly drop that voltage to an operating voltage of 13.6 - 13.8 volts as they are designed to. its a fuel saving / emissions concept. flawed in my opinion but thats what we have to deal with. 13.8v will just be enough to keep the traxide happy and link the batteries but over a period of time it wont be enough to allow bulk charge and this will diminish the battery's capacity over time. The Optima is a good choice here but over time it wont last either.

      yes DCDC chargers dont like heat and mounting them above the battery is a bad idea they get too hot and reduce output accordingly. plenty of other places to mount them.

      There will always be two opposing points of view on this topic , a bit like pre / post filter systems lol.
      2016 GX , in White


      • #4
        13.8 volts is enough to maintain a charge in the second battery but for a decent absorption stage needed for a deep cycle a minimum of 14.2v is normally required to give full charge capacity. That higher voltage is needed to maintain current flow into a battery that has increasing internal resistance. Otherwise a full charge will be short.

        it will still charge but not to full capacity

        thats some basic theory behind battery charging and current flow


        • #5
          Hi mate I don’t know anything about traxide but in my opinion it sounds like he is a good salesman. Our cars have a smart alternator so when our starter battery is full it will drop the volts and only charge in the 13v zone.

          To my my understanding this will affect the amount of charge for your auxiliary battery/s and by far the best solution is a dc/dc charger which will boost the voltage back up for optimum charging. Most dc/dc chargers are also an isolator so your starter battery cannot go flat from running accessories. They also have an inbuilt mppt solar regulator (most of them these days). And lastly they are generally a 3 stage smart charger to look after your auxiliary battery/s for longer lasting life.

          I think ink there is a reason why all the big tourers all have dc/dc chargers and I would highly recommend getting a redarc one. You can mount them on a bracket they make on the front of the car so heat doesn’t effect them


          • #6
            Its not that hard to have the dc-dc charger in the cabin, avoiding all the issues of heat on them. I think having a dc charger thats bumping my deep cycle to 14.2v for charging is a good thing. Plus the solar input means the 2nd battery never goes flat


            • #7
              Plenty of discussion in this thread on Pradopoint:
              24 pages in fact!




              • Spook1205
                Spook1205 commented
                Editing a comment
                Defiantly pop corn grabbing drama there!
                The guy that sells them (Leigh?) really seems to know his stuff and has tested the system as you say.

                I wouldn’t of thought that you could fully charge your deep cycle with the low voltages we have but in saying that I am more than happy to learn new information and change my thoughts.

                So maybe Rich you don’t need one at all....

                I am just glad the popcorn grabbing drama isn’t on this forum

            • #8
              I have a Century N70 second battery , kept fully charged by an Ironman 40A DCDC , mounted vertically in front of the main battery , behind the headlight. This keeps it in the airflow and allows the cables to be kept short. The DCDC has a remote isolate switch , auto jump start , remote voltmeter and remote status LED , so i dont need to open the bonnet to see how its performing. When engine is started there is a 5 second delay then the voltage initially rises to 14.6V then will stabilise at 13.8 once the second battery is happy.
              the dual solenoids which control the battery are mounted next to the radiator .

              all being said , once the car is out of warranty i'll be disabling the smart alternator function.
              2016 GX , in White


              • #9
                Leigh's mod is just a diode inserted in series with the ALT fuse and only applies to the earlier non ECU controlled alternators. wont work on ours
                2016 GX , in White


                • Silverfox1111
                  Silverfox1111 commented
                  Editing a comment
                  I've read that ford rangers can have their smart alternators work like a traditional alternator by the dealer reprogramming the ecu. Maybe it can also be done on toyota fortuner/hilux alternators.

              • #10
                im not sure about the Toyota one , i dont think it can be turned off i cant get anyone to confirm. Im disabling mine by rewiring the internal regulator , should work
                2016 GX , in White


                • Spook1205
                  Spook1205 commented
                  Editing a comment
                  How about change the PWM with an external divice?

              • #11
                Havent looked into that yet Luke , Im hoping it will be a case of rewiring or using an internal regulator from a non DPF model. and then finding a way to remove any fault codes.
                2016 GX , in White


                • Spook1205
                  Spook1205 commented
                  Editing a comment
                  If it will help I can measure the PWM / Duty cycle on a specific voltage forced up by scan tool

              • #12
                Thanks , that would be awesome , if i know what i need to inject to make the voltage rise higher then i can trick the alternator into doing so. Still need to stop the ECU throwing a code though.
                2016 GX , in White


                • #13
                  I fitted an auxiliary battery a week after buying Finn (Blue coloured Tuna, get it?). Could never get my fridge to run more than 1 day in eco mode when camped up and not driving for a few days..

                  Bought a Ridge Ryder 20amp DCDC from Supercheap and mounted it on the side of the batter tray just like Toyota do with their overpriced Redarc setup.
                  Now get 2 and a half days before the fridge stops at the 11.5V setting.

                  The DCDC died in less than 2 months (15,000km). Visited an auto elec in WA (I was doing the big lap) and he said never put electronics in the engine bay of a diesel, the heat cooks things.

                  Returned it to SCA in Vic (cause strangely WA doesn't have SCA) and the refunded me in full as they were out of stock.
                  3 weeks later I bought another from SCA and this time mounted it under the front passenger seat.
                  Ran a single 6 gauge wire from the crank battery through the firewall to the DCDC and then a single back to the aux batt.
                  Negative was to the chassis at the aux and at the DCDC.
                  Been a full year without any probs.
                  What I like about the SCA unit is it has an auto turn on at 13.2V and an auto turn off feature at 12.8 volts.
                  Parasitic draw when off is just 3mA. No need for a VSR or connection to ignition.


                  • #14
                    Finn! That is gold mate👍


                    • #15
                      Originally posted by Hylife View Post
                      What I like about the SCA unit is it has an auto turn on at 13.2V and an auto turn off feature at 12.8 volts.
                      Parasitic draw when off is just 3mA. No need for a VSR or connection to ignition.
                      That is a good feature , but in my opinion there will be times when you will need to turn off the DCDC - such as whenever there is no second battery connected , or if the second battery craps out.

                      2016 GX , in White