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Dual Battery - Power in the bus

Discussion in ''How To' & 'Handy Hints'' started by Marty, Aug 1, 2008.

  1. Marty

    Marty Active Member

    Messages:
    2,290
    Location:
    Sunny Melbourne
    I just thought I'd show you guys how I had put power in the bus.

    I had been given a battery isolator so I put that in, grounded it to the chassis, later hooked it up to the positive termials of battery 1 & 2.

    [​IMG]


    I then put in a heavy duty second battery, grounded it to the chassis and later run all the cables (cable-tied the cable from the isolator so it would be out of the way).

    [​IMG]


    I then hooked up the positive from battery 2 to an inverter, secured in the spare wheel well (and grounded to the same point as battery 2). Now I can plug in anything while camping and it's all hidden under the bed. :)

    [​IMG]
     
  2. ttmck

    ttmck Super Moderator Staff Member

    Messages:
    2,733
    Location:
    Hallett Cove STH AUS
    Thanks for sharing Marty , sticky on this good info
     
  3. BIGBUB

    BIGBUB New Member

    Messages:
    269
    Location:
    Melbourne - Wantirna
    hey marty, what's the voltage for the power inverter?? i went to Jaycar and they said i needed to buy a 600Watt inverter if i wanted to run a latop, or tv, etc.
     
  4. Marty

    Marty Active Member

    Messages:
    2,290
    Location:
    Sunny Melbourne
    I can check for you tomorrow but it's only a small one - 100W or so but I was told it was enough for running a laptop or similar though haven't been campign since i put it in so haven't tried it.
     
  5. Sheriff

    Sheriff Active Member

    Nice job Marty!...what do you have hooked up to the second battery...or is it just for the inverter?
    Does that little gizmo isolate the starting battery or do you manually flick a switch?
    Rich
     
  6. grapeape

    grapeape Member

    Messages:
    262
    Location:
    Adelaide Hills
    let there be light!

    Very interested in this Marty.

    Was wondering how it could be altered to have multiple outlets?

    I have one of those inverters as well, $60 from Dick Smiths, but would like to wire another permanently.

    Is there a switchy thingy to stop draining the main battery or does this isolator thingy do that??

    Just an echo of Sheriff's question I guess??

    Richo
     
  7. Marty

    Marty Active Member

    Messages:
    2,290
    Location:
    Sunny Melbourne
    The job of the isolator as I understood it was so that both batteries are charged when the engine is running, but power won't be drawn from the first battery. You can put in a switch to crank from the second battery too, but I haven't put that in.

    Not sure about multiple outlets, I have seen inverters with more than one outlet around so that could be an option?
     
  8. Sheriff

    Sheriff Active Member

    That is defintely a feature of many Rich...preventing the starting battery from being used! It can either be electronic...i.e. - stop your bus and the switch will automatically isolate your starting battery and operate from the second.
    There are also some that will drain a % of the primary battery and then when the acceptable level has been reasched to still start with no problems...it will kick over to the second batterry...thus giving you 1.5 worth of power time.
    There are also manual isolators...where you need to switch from on to the other when you make camp.
    Hope that answers your question?
    Rich
     
  9. drivesafe

    drivesafe Member

    Messages:
    103
    Hi Bubdub, before you get your inverter, first check the power requirements of what ever you are planning to run off the inverter.

    Workout which device draws the most power and then buy an inverter that has a constant output of at least 50% high than your hungriest device.

    EG, if your TV requires 200w than get a 300w inverter.

    There are a number of reasons for getting a bigger inverter than what is needed. Many inverters start to loose their AC characteristic when you get close to their maximum output, this can lead to premature failure of the inverter and damage to the device being powered by the inverter.
     
  10. Necro

    Necro Active Member

    Messages:
    2,623
    Location:
    Victoria
    Hmm two batteries....I would love that...
    Stop me worrying about running the lights when I go camping...
    Never worked out how many hours the 12v light works before the power runs out...
    Gives me the jeebies, I always want to turn it off worrying Lulu won't start when it's time to go home....dunno about a tv or a laptop though....i prefer a campfire...
     
  11. T1 Terry

    T1 Terry Active Member

    Messages:
    1,309
    Location:
    Lake Illawarra NSW
    House Batteries

    The isolator mentioned is a voltage sensing relay, it requires 13.8v to be at the start battery before it will join the 2 batteries together. This ensures the start battery is fully recharged before the house battery starts charging, it also give you the surface charge from the start battery that you can use as the relay will stay connected till the battery voltage drops below 12.8v. This is adjustable and can be brought down lower to say 12.4v which is 50% of the stored energy in the battery. Flooded cell batteries should not be pulled down below 50% capacity as it does permanent damage to the battery.
    There are 2 main types of battery, cranking batteries and deep cycle batteries.
    Cranking batteries are cheap and not much use for house batteries, they have a large short term output capacity but very little storage capacity.
    Deep cycle batteries are the opposite, they will be damaged by very heavy load discharge but can provide a lot of light discharge energy to maintain lights, fridges etc for long periods.
    Never plug more than one class 1 appliance into an inverter at any one time, the risk of electrocution becomes a very real threat in this situation. A class 1 appliance is one that uses an earth to the body of the appliance such as toasters, fridges, frypans etc. If it has 3 pins on the plug it is most likely a class 1 appliance.
    Don't hard wire these little inverters, the reasons are complex but I will explain best I can if anyone wants to know why or even better I can try to get another KC member to explain who is really up to speed on this stuff.
    There is a heap more info about running house batteries, I can start another thread if anybody is interested. Then there is LED conversion and .......

    T1 Terry
     
  12. drivesafe

    drivesafe Member

    Messages:
    103
    Hi Terry, just a couple points, very, VERY few dual battery isolators wait till the cranking battery is fully charged before connecting the auxiliary battery.

    In the vast majority of cases, isolators have no way of knowing what state a cranking battery is in, they simply monitor the voltage level on their input.

    When a motor is started, the alternator spins up to operating voltage in a few seconds. This operating voltage is usually between 14 and 14.2 volts.

    Most new isolators are now set to connect the auxiliary battery once the voltage on their input reaches 13.2 volts, and as such, the isolator will connect the auxiliary battery shortly after the motor is started.

    There are a few isolators that have a 30 to 60 second delay but this delay is still initiated once the vehicle’s voltage rises above 13.2v.

    Next, a battery with a State of Charge 12.4v is actually at 80% and a battery with an SoC of 12.0v is at 50%

    Also, taking a flooded wet cell battery down to 30% ( SoC of 11.75v ) will not actually damage the battery but will shorten it’s life and while this may seem like double dutch, you need to know how many time you can take the battery down to 30% before the battery can no longer hold 80% or more of it’s total capacity when fully charged.

    The battery may only tolerate 100 cycles down to 30% before it fails to hold 80% or more of it’s original capacity.

    The point is if you go out every weekend and discharge the battery down to 30% SoC, then you can expect the battery will need replacing after only two years of use. In this type of use it would be better to make sure you don’t discharge the battery below 50%

    If you go out once a month and discharge down to 30%, then you can expect to get 8 years out of the battery, except that few battery will last that long any way so there is a tad more to how deep you discharge a battery and when you will need to replace it.
     
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  13. Joels73 Panel

    Joels73 Panel Active Member

    Messages:
    1,218
    Location:
    Somerset, Tasmania
    How would you go if you had the 240 hookup? Could you make it so the 240 took over from the second battery and powered the tv etc which it wired to the aux battery? Also is it the same with a generator?
     
  14. london_mike

    london_mike New Member

    Messages:
    350
    Location:
    VIC 3071
    Nice photos. I recently bought a solenoid; it came with instructions, but photos are always better. :)

    I was wondering what size wire you used to connect the two positives ?
     
  15. london_mike

    london_mike New Member

    Messages:
    350
    Location:
    VIC 3071
    Hi, All good advice, thanks. Can you recommend any particular makes/brands of deep cycle battery?
    Something that's good value for money - cause I haven't got much of that. :D
     
  16. rat55

    rat55 New Member

    Messages:
    13
    Location:
    Brisbane
    There is no battery that will last for eight years, sorry to say mate
     
  17. syncro

    syncro Well-Known Member

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    Location:
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    Genuine VW last 7.
     
  18. Kombi Dad

    Kombi Dad Well-Known Member

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    2,402
    Location:
    Bungendore, NSW
    My AGM (the second battery) has been there since this time in 2006. Only 7 years so far.

    Ian
     
  19. rat55

    rat55 New Member

    Messages:
    13
    Location:
    Brisbane
    I have heard of battery's lasting over ten years but is rare, batterys normally will last the warrenty two to three years but if they are maintained they can last longer. It is all about the plates inside the battery.
     
  20. syncro

    syncro Well-Known Member

    Messages:
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    Location:
    Southern Highlands
    It's all about the treatment and quality of the battery.
     

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