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Thread: E23 Move Battery To Rear??

  1. #1
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    E23 Move Battery To Rear??

    There's a turbo on my 728i and the washer bottle has lost it's space. In addition I'm trying to mount a 3/4 gallon methanol bottle somewhere. The obvious thing to do is move the battery to the trunk like a 2002.

    Is there a kit/bracket/plan for doing this like for the 2002 or shall I just do it?

  2. #2
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    the south african 745 had the battery in the trunk, as did the e24/28 M cars. You might be able to find some parts/battery cable off parted out M5/6's but probably easier just to get an aftermarket kit.
    Mike
    93 M5 3.8 Sterling Silver/Black (euro)
    94 M5 Touring Madeiraschwarz/Black
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  3. #3
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    My beloved mechanic trotted out a used coiled cable yesterday and said "here", thinking it was a simple cable long enough to do the battery move. Upon closer inspection it's a long OEM battery cable all right, with a molded positive terminal at one end and a clamp at the other, but it's folded in half with heavy heat shrink and has what looks like a race car cutoff switch - with no key present - at the halfway point.

    It's a factory part, not made-up, and it looks like a way to put a battery cutoff in the cockpit of a race car. Given that he only works on German cars, it's either from a BMW or a Benz. He can't remember where it came from.

    Any clues?

  4. #4
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    Overall length and distance from terminal to switch are going to be your critical factors.
    You'll have to decide where in the trunk to put the battery.
    In the M5 its where the spare tire is for the E23, and you have the fuel fill on the drivers side.
    You are then limited to between the strut towers like the 2002 versions, perfect for integration with a rear strut bar.
    --Jay3->Sic gorgiamus allos subjectatos nunc
    84 €735i manual, 88 528e/i
    Motronic 1 and 1.3 wiring
    Transmission & Diff gearing sheet

  5. #5
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    Is there a rear strut bar for an E23?

    I tore into OEM under ZA 745 1984-86 and can't find anything at all about cables. There's a picture of a battery with the normal single bolt tie-down, but that's it. Couldn't see a cable or a battery location. Mmmmph.

  6. #6
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    I have an e30 battery cable but don't think it'll be long enough even to go in between the rear struts- Do some checking on that and let me know, it's packed away and don't have easy access to it.

  7. #7
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    I was pretty sure a rear strut bar was part of the tow package, but maybe thats only on the E28.
    But any decent fabricator should be able to weld a bar between 2 flanges.

    Dave, I'm with ya, I seriously doubt an E30 cable would come close to working as it came from the car...
    BUT
    If you cut it and install a battery cutoff in the cabin, you can splice in some extra length, probably 2g power wire would work great.
    --Jay3->Sic gorgiamus allos subjectatos nunc
    84 €735i manual, 88 528e/i
    Motronic 1 and 1.3 wiring
    Transmission & Diff gearing sheet

  8. #8
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    That's what I'm thinking. I even have some cable left over from one of the race cars. I guess the battery mounting is the issue.

  9. #9
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    What about a cable out of an e38?

    Sent from my HTC6545LVW using Tapatalk

  10. #10
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    00 MRoadster '83 745i,
    Custom cables are not that expensive. I relocated the battery on my old farm truck. Bought a custom made 00 gauge cable about 7 foot long, and it was less than $50.

    Figure out where you want the battery, Mock it up, run a piece of rope or string to figure out the overall length, and order what you need.

  11. #11
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    What's a pro-tip on how to mount the battery? Freestanding in the rear center of trunk hooked to the floor? Against a vertical with a side strap? In a box? I hunted for a rear strut bar to copy the 2002 rear battery setup but the bar looks like either Germany or fabrication and welding.

    I can figure out the cable I think. I'm going to use the one Roberto gave me if the shutoff ends up in a decent place, like under my seat. Very cool piece.

  12. #12
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    Cable from a late e30 4-door should get you from trunk to firewall, then do a junction box near the strut tower. This is what I used in my e28.

  13. #13
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    OK. Parts in hand and ready to go. I bought a marine battery box and I'm going to try to use the above-referenced cable.

    QUESTION: What's the approved way to get the cable from the trunk between the shocks to the LF headlight? Inside the car? Under the car? In an armored flex?

    I'd rather go under if I can because I know all the plastic will explode if I disassemble the thresholds etc.

  14. #14
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    I would run it along the drivers door sills, inside the cabin.
    The E28 M5 with trunk mounted battery ran the cable under the car part of the way.
    if you want to run it outside make sure to get a water tight grommet wherever you drill the hole.
    --Jay3->Sic gorgiamus allos subjectatos nunc
    84 €735i manual, 88 528e/i
    Motronic 1 and 1.3 wiring
    Transmission & Diff gearing sheet

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