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HELP Dual Battery (need info)

Discussion in 'Information For Newbies' started by Holden0018, Feb 15, 2017.

  1. Holden0018

    Holden0018 New Member

    Hi all i am new to the dual battery scene and am wanting to eventually when i get a 4wd set up a dual battery to run, 40l fridge (thinking of getting engel have heard nothing but good things about them) and a few camp lights and chargers for phone.
    This is my understanding of a set up:
    Main battery -
    DC TO DC Charger - wanting to know peoples experience with brands have heard of redarc. also brands to stay clear of
    auxillary battery in a battery box (agm, lead acid, calcium?, deep cycle battery) - peoples experience with size and brands to stay clear of
    appliances (fridges, lights, chargers) - also is there a 'thing'not sure what it would be called maybe a 12volt panel that if you were to mount a auxillary battery under the bonnet how does it give power to the appliances considering it isnt sitting in a battery box. like is there a battery box type set up with 12v socket, anderson plugs and usb ports that can be mounted into a tray of ute.

    i am wanting a set up for a weekend camp around so wanting to stay clear of solar. would be camping for a weekend with driving in between so im thinking a 100ah battery or 120ah battery should be sufficient if set up to charge from dc to dc would last a weekend away powering a fridge 40l and a couple of camp lights and phone chargers.

    also i have seen mixed reviews about AGM batteries they seem to be the go and some have said they cant be ruin empty where others have said it is fine to run them empty and there is no harm.

    one last question i have seen australian direct do a complete kit is this an easy option then i could take to auto elec to install

    what have others payed for their set up and if so could you talk me through it

    THANK YOU for your input is it much appreciated

  2. Tink

    Tink Well-Known Member

    Would be good to lnow the make, model and build year of your vehicle forst.
    Bomber2012 and Albynsw like this.
  3. Holden0018

    Holden0018 New Member

    2010 Toyota hilux
  4. dare

    dare Member

    The biggest consideration is how long you want to be able to be parked up for.

    An ordinary N70zz cranking battery and a VSR will easily do the job if you're into overnight or weekend stays. This will be a fraction of the cost of a DC to DC charger and deep cycle battery.

    DC to DC chargers have the advantage of fully charging batteries no matter what type they are. It will get the maximum charge and maximum life out of your battery. It's not recommended (though people do) to use dissimilar batteries with a VSR.

    Personally, even if using a DC - DC charger I'd want the second battery to be something that can be swapped with the cranking battery for redundancy. Swapping batteries has saved my bacon once.

    For getting power from the battery to the accessories many take power from the battery into an auxiliary fuse box and then take power from there. That way you don't get the big mess of inline fuses and wires hanging off the battery and it's a lot easier to manage. For my landcruiser I just have some 6mm wire going into a quad cigarette lighter panel (which also has 2 usb ports) mounted near the gearstick with an in line fuse. I put it in the morning before a 3 week trip and haven't seen a need to change it, it does everything I want and has next to no volt drop.

    What fridge is best is always a contentious matter on 4WD forums, kind of like asking about tyres or oils. I did a lot of research before buying one and I really like my Bushman fridge, it's one of the most efficient around and it works really well for us.

    For the fuse for your fridge consider getting an automatically resetting circuit breaker. They slip in where a blade fuse goes and if anything goes wrong you've got much more of a chance of still having good food at the end of it!
  5. Tink

    Tink Well-Known Member

    Umm, a VSR is either open or closed, it doesn't care what type or sise of the batteries it is connected to :)
  6. Bomber2012

    Bomber2012 Well-Known Member

    If you are going to go down the battery box path , I recently bought a battery box rather than a fixed 2nd battery , i bought a projector battery box that came with a 130 amp hour AGM battery that cost $360 for both . the box has a ciggie lighter outlet , merit plug , positive and negative studs , 2 anderson plugs and an LED battery charge meter . I haven't yet wired it up to the alternator and have had a few trips out for the weekend and the battery has been fine running my 40l fridge for 3 days , i will wire the 2nd battery to the alternator eventually but for 3-4 day camps it does the job at the moment . I looked at most of the battery box options and asked for advise from the forum and found this set up ideal , basically it depends on what sort of use you need it for , if your planning on spending long periods out in the scrub then spend the coin on a good system if , like me your only spending a few nights out save your money and buy a basic set up .
    hope this helps .
    Last edited: Feb 15, 2017
  7. Bomber2012

    Bomber2012 Well-Known Member

  8. Critter350

    Critter350 New Member

    Your kinda right Tink, but different battery types like different charge rates, so an AGM won't get a full charge when paralleled with a wet cell.
  9. Critter350

    Critter350 New Member

    DC DC chargers are expensive. If your touring for a week or more at a time they might make sense, but not for weekends away like Bomber says. The mixed battery type isn't such a big issue if your using it like that. Charge it up before a weekender and your set. 'Empty' for a battery is 11.8V. You can run a deep cycle down to this without hurting it too much. Running it lower will kill it quickly. Australian Direct has a heap of YouTube stuff that will tell you what you want to know
  10. Tink

    Tink Well-Known Member

    Sorry mate, you are confusing things.
    The alternator supplies the charge. A VSR does not charge anything. It is either open or closed, nothing more.
    Yes, different batteries like different charge rates. But both are lead acid batteries so are perfectly OK to be charged together. They are the same "type" of battery.
    A flooded wet cell lead acid battery prefers a 14.8 volt charge rate. An AGM VRLA battery prefers a 14.4 volt charge rate. Now I don't know about your vehicle's alternator but mine outputs a constant 14.1/14.2 volts, so is not perfect for either.
    In summary, charging a flooded wet cell and an AGM, linked in parallel, off your vehicle's alternator, as long as it is not a variable voltage alternator, is perfectly OK. Just top them both up every other month using a good quality, multi stage, 240 volt smart charger.
    And yes, an AGM, due to how it accepts the last 5% of its charge, will not fully charge off an alternator. But it will get very close and it will never be an issue if you top up (see above) every other month. An AGM being paralled with a flooded wet cell and not reaching 100% charge has nothing to do with the VSR.
    hiluxdriver likes this.
  11. axle82

    axle82 Well-Known Member

    thats all i have in my cruiser and it works absloutly fine. have had it in there for about an year now without any issues. as stated every month or so i top it up with the 240v ctek charger
  12. Fittster

    Fittster Member

    Hi Holden,

    I understand that you may have finished your install now but this extra information might help others that stumble across this thread.

    I literally just finished installing my dual battery setup on the weekend. I read a lot online and there are a million opinions etc and so went direct to Battery World (I'm just out of Canberra) and spoke to an auto electrician there. Between the stuff I read online and the holes he filled I had a really good understanding of what I needed and why.

    One thing to note is you might want to find out if you need a DC-DC charger or like me, a BC-DC charger. After a certain year (I thought it was 2006?) alternators no longer gave enough charge to FULLY charge a battery. Therefore your AUX battery will never make it to 100% on a DC-DC charger. The BC-DC charger has some magic so the alternator charges your AUX to whatever capacity it can, then the BC-DC charger draws that little bit more from the main battery so you get full power. Because mine only turns on with the ignition, my main battery can never go flat. I went with the Redarc BC-DC 1220. The next one up allows you to use a solar panel direct but since my solar panel already has the computer stuff to control charging, I can plug it direct onto my battery so could go the cheaper version (which is still expensive!).

    My needs are primarily for a Waeco 65DZ fridge (dual zone) which may be in the camper trailer being towed, or the back of the Pajero. I also wanted to be able to charge my battery in my camper trailer while driving.

    So... I have the battery in the engine bay. I was told to stay away from AGM because they die too quickly and to use a calcium battery. Sadly I don't have much room and so only have an 85A/H but I'll get to the performance at the end. Either way, go the 100 or 120 for sure.

    The Redarc sits between the main and the AUX but it needs to be within a meter from the AUX to ensure maximum charging efficiency. I then have 6mm cable running to the back of my car and an anderson plug on my tow bar. This allows me to plug into my camper for charger while driving. I also ran smaller cable to the rear third seats and changed out the cig plug that was there for an acc plug and added a dual USB plug. This was because the original cig plug only works when the car is on, now my new setup works all the time direct off the AUX battery. The acc plug I was told can handle more power than the standard cig one that was there too.

    Yesterday I did a lot of driving around and when I got home tested the AUX battery which was fully charged. I then plugged in my 65lt fridge/freezer into the acc plug I installed and set it to -16 degrees. I went and checked just just now and it's still running - 15 hours later. Of course there will be other factors like hot days, full fridge, opening and closing the lid etc but since I have my solar panel I can just charge the AUX when I'm not driving, or keep the fridge in the car when doing a little drive while camping.

    Hopefully some of this is helpful, but I do suggest just having a chat to an auto electrician as it helped me lots. I build websites for a living and the fact I could do all of this on my own goes to show that ANYONE can, just by asking a few questions.

    tankbloke likes this.
  13. stevemc181

    stevemc181 Well-Known Member

  14. Fittster

    Fittster Member

    Yes you are definitely right, I went offline a little bit there, it's a DC to DC charger. I was too busy getting the model/name mixed up with what it actually does!

    Mine was the 20A version - which doesn't have the solar input regulator since my panel already has that built on the back of it.
  15. stevemc181

    stevemc181 Well-Known Member

    Generally you would be far better off with the MPPT supplied in the Redarc units, they are usually much higher quality than those supplied with panels. You should also remove the solar regulator from the panel and put it as close to the battery it is charging as possible.
  16. Fittster

    Fittster Member

    I like that idea much more. The battery etc in the trailer all look dirt cheap and I haven't really given it a proper workout to see how it performs but if I can get the cash together, a decent upgrade to decent everything in there would be the way to go. I'd then opt for one of the other Redarc's like you pointed out and take the regulator off my panel completely.

    We are off to Alice at the end of Sep so will give it a good go then, see what it can/can't handle. We aren't staying anywhere crazy, all touristy places (have to keep the kids and wife happy for their first outback trip!) so I don't actually need this setup, but I'll use it for a test regardless.

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