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Thread: Dual battery in cargo area

  1. #1
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    Dual battery in cargo area

    Hi there,

    ive got an Engel smart battery box in the cargo area and want to run 6b&s cable from cranking battery to cargo area passenger side. Anyone got tips on best route? Also looking for an earth point in the rear left of the cargo area. Pics?

    any help much appreciated.

    triplezed3

  2. #2
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    I think that Tim from Traxxide (AULRO: Drivesafe) might have some pics in PDF format.
    "Land Rover - making mechanics out of everyday motorists for nearly 70 years"

  3. #3
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    There's just the one hole in the firewall on the driver's side, and it's tricky to get behind the dash.

    Once you get to the passenger side, under the door "steps" there's a rather large channel/duct you can use that will take you all the way to the rear. You need to remove all the trim to get down to the metal.
    You may want to route the cable up the driver's side, and just cross it back when you get in the cargo space.

    And if I recall correctly, there is an earth point in the rear.
    If at first you don't succeed, that's one data point. - xkcd
    ----------------------------------------------------------------------
    2011 Discovery 4 SDV6 HSE

  4. #4
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    I have the same bulk head penetration and cable route problem.

    Problem is you want to run a big gauge cable along the shortest route to minimise volt drop and the drivers side little grommet is just not that big and already have some wiring through it..

  5. #5
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    Quote Originally Posted by HarryO View Post
    I have the same bulk head penetration and cable route problem.

    Problem is you want to run a big gauge cable along the shortest route to minimise volt drop and the drivers side little grommet is just not that big and already have some wiring through it..
    Use the second one near the throttle pedal

  6. #6
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    Quote Originally Posted by HarryO View Post
    I have the same bulk head penetration and cable route problem.

    Problem is you want to run a big gauge cable along the shortest route to minimise volt drop and the drivers side little grommet is just not that big and already have some wiring through it..
    Ah yes, the search for the impossible zero voltage drop.

    I just measured my aux battery at 12.03V (yes, it's not fully charged).
    The fat cable supplied in the Traxide kit runs from there, next to the crank battery, around the engine bay and up the driver's side as described to the jack cubby in the cargo space. Some 4m worth?
    Measured voltage there is 12.02V. In fact, it kept flicking between 12.03 and 12.02, so we could say 12.025?
    I have another 6G cable Y-ed from that point about 2m long running to the passenger side. Exact same reading.

    For all practical intents and purposes, that's 0.01V over 6m of cable.
    IMHO, to get any better ain't worth the hassle.
    If at first you don't succeed, that's one data point. - xkcd
    ----------------------------------------------------------------------
    2011 Discovery 4 SDV6 HSE

  7. #7
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    I have the Engel smart battery pack in the back of mine, strapped to the floor just in front of my rear drawers and fridge slide. I also have two batteries under the bonnet, with the Traxide set-up through the vehicle.

    The instructions that come with the Traxide kit are very detailed and come with photos - running the cabling through to the rear of the car and installing outlets in the luggage area is very easy if you follow these instructions.

  8. #8
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    Quote Originally Posted by Redtail View Post
    Ah yes, the search for the impossible zero voltage drop.

    I just measured my aux battery at 12.03V (yes, it's not fully charged).
    The fat cable supplied in the Traxide kit runs from there, next to the crank battery, around the engine bay and up the driver's side as described to the jack cubby in the cargo space. Some 4m worth?
    Measured voltage there is 12.02V. In fact, it kept flicking between 12.03 and 12.02, so we could say 12.025?
    I have another 6G cable Y-ed from that point about 2m long running to the passenger side. Exact same reading.

    For all practical intents and purposes, that's 0.01V over 6m of cable.
    IMHO, to get any better ain't worth the hassle.
    It just doesn’t work like that. Voltage drop is related to the current being drawn through the cable. You could use a single strand of wire and achieve the same result you did but that doesn’t mean it’ll charge a car battery.

    A voltmeter measures the voltage potential but uses an extremely large resistance to do this so as not to affect the actual circuit itself eg 10 megohm. If no current is flowing in the wire creating a resistance, the voltmeter won’t see any potential difference.

    You are trying to use the correct gauge wire that will meet your current needs over the length of wire so that the voltage at the end isn’t too reduced so that your battery won’t charge correctly.
    2010 TDV6 3.0L Discovery 4 HSE
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  9. #9
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    Quote Originally Posted by DiscoJeffster View Post
    It just doesn’t work like that. Voltage drop is related to the current being drawn through the cable. You could use a single strand of wire and achieve the same result you did but that doesn’t mean it’ll charge a car battery.

    A voltmeter measures the voltage potential but uses an extremely large resistance to do this so as not to affect the actual circuit itself eg 10 megohm. If no current is flowing in the wire creating a resistance, the voltmeter won’t see any potential difference.

    You are trying to use the correct gauge wire that will meet your current needs over the length of wire so that the voltage at the end isn’t too reduced so that your battery won’t charge correctly.
    Good point. The 6G cable should have low enough resistance still not to cause any issues over that length.
    Mine draws around 20A while charging, peaked at 31A on one test run.
    Tim advised the USI160 could easily push 35-40A peak once I've reconned my battery from sulfation (but that's another story).

    Some actual measurements of voltage drop say per metre of cable would be handy, but I suspect it's probably negligible going from around 4 to 6m?
    If at first you don't succeed, that's one data point. - xkcd
    ----------------------------------------------------------------------
    2011 Discovery 4 SDV6 HSE

  10. #10
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    Quote Originally Posted by HarryO View Post
    I have the same bulk head penetration and cable route problem.

    Problem is you want to run a big gauge cable along the shortest route to minimise volt drop and the drivers side little grommet is just not that big and already have some wiring through it..
    done it! Ran the cable from cranking battery thru another grommet big enough for 2 x 6b&s cables (above the accelerator pedal) and then across dash and under the door sill - (got the tip from Tim @ Traxide). All neatly tucked away through to the cargo area. All up, under 6m of cable.

    Not sure if there’s any voltage drop worth worrying about as I’ve also rigged up a solar panel which is on roof rack permanently which will help when I’m stationary.

    Really pleased with end result and appreciate everyone’s help. Thank you

    zzz

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