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Do i tranfer my battery to the boot OR put a light weight one in the front?

Discussion in 'A3/S3 Forum (8L Chassis)' started by Don's A3 TTu, Jan 21, 2011.

  1. Don's A3 TTu
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    Don's A3 TTu Member

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    first how easy is it to tranfer it to the boot? mounting, wiring etc....
    how much lighter is a racing battery?
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  2. s3dave
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    s3dave TFSI Hybrid

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    The mounting should be no problem, i would recommend getting a metal tray fabricated for it to sit in just in case the battery decides to have a wee..;).... it is the run of the thick battery leads that will be an ass.....
    Last edited: Jan 21, 2011
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  3. steve bain
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    steve bain Member

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    battery should be externally ventilated also if i remember correctly too.
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  4. future
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    future Scuderia Vittoria Edition 001

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    or you could put a lightweight one in the back and have best of both worlds? I have wanted to relocate mine for a while but cant seem to find much on the subject, anyone got a walk through? (sorry to hijack the thread thought it might be useful to you aswell don:))

    tom
    Last edited: Jan 21, 2011
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  5. <tuffty/>
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    <tuffty/> Badger 5 Edition Staff Member Moderator

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    In both the recent battery relocations I have been involved in used a battery box from Demon Tweaks and 50mm welding cable for the run to the front...

    The Mk2 Golf in the workshop at the moment has a steel tray to sit the battery box in which will be held in with straps... scrutineers can get funny about insecure and uncovered batteries...

    <tuffty/>
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  6. Don's A3 TTu
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    Don's A3 TTu Member

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    light weight in the boot may be an idea depends how light the battery it cos ide only move it to even out weight distribution and 3 metres of thick battery cable would probably be quite heavy
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  7. dany2k
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    dany2k Member

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    what an interesting idea. i could imagine you showing your engine bay to kids and wowwing them with your battery-less car.
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  8. s3dave
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    s3dave TFSI Hybrid

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    BMWs have done it for ages, simple amp installs.....
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  9. Prawn
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    Prawn My other car is a MINI!!!!

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    As said above to a lightweight battery install behind the front seats.

    Best place to mount it I'd think is behind the passengers seat, or if ease of charging is important, in the boot somewhere.

    if you get a Drycall battery it can be mounted on it's side too.

    I use a PVR25 in my Mini, and it weighs 6kg, compared to 19kg for the original battery! Massive weight saving there. Won't have any trouble starting a 1.8T either.

    Also, if you put the battery in the back you can plumb in a cut off switch en route to the front again!
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  10. s3dave
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    s3dave TFSI Hybrid

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    Dont forget it will need an in line fuse just in case it earths some how under the carpets/through the firewall etc.
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  11. Don's A3 TTu
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    Don's A3 TTu Member

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    i have no carpets so thats one worry out the way

    in line fuse cool ok
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  12. future
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    future Scuderia Vittoria Edition 001

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    true, would even out your weight distribution and lightweight battery should over compensate for the cable :) this was my plan anyway lol just need to know where to get the cable from.

    tom
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  13. Don's A3 TTu
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    Don's A3 TTu Member

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    pvr25 and will it fit behind the passenger seat ok?
    i suppose its only a small little thing

    ive still got my dvd head unit in my car will it be ok with the pvr25?
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  14. Prawn
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    Prawn My other car is a MINI!!!!

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    yea, it'll be fine. Once running you're feeding mainly from the alternator, it's a fairly high output alt, so there should be more than enough juice to still power the ECU, all ancillaries, and still have enough left over to charge the battery
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  15. jcs356
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    jcs356 Brum brum

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    Here's my install in my old Ibiza. No problems with MOT or on track days. Will be doing the same to the Cordoba in the spring.

    Battery was on nearside rear held down by two ratchet roofrack straps that were riveted to the car floor.

    [​IMG]

    Put a double post terminal under the bonnet so I could leave all other wiring as was.

    [​IMG]

    Just remember to go for the right core cable. I think mine was 0 AWG from memory - or welding cable as someone else suggested.
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  16. s3dave
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    s3dave TFSI Hybrid

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    50mm?? surley not, thats 2 inch, it would way more than the car....lol
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  17. jcs356
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    jcs356 Brum brum

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    I assume he means 50mm2.

    Just checked and:
    0 American Wire Gauge (AWG) = 0.3249 inches diameter = 8.25mm diameter = 53.45 mm2 cross sectional area
    Last edited: Jan 21, 2011
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  18. Audi2ptzero
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    Audi2ptzero Member

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    Best to go with a slightly smaller one in the back since you are going to add some weight with a sealed box and having to run a long cable back up front.


    If you track the car I would suggest you look at any rules on how the box needs to be mounted.
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  19. jcs356
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    jcs356 Brum brum

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    As per my previous post, no issues with any of the 15+ track days I did with my battery located in the boot.

    Also in terms of battery size - it also depends on what you are aiming for. With my Ibiza it was notoriously tail happy - so aim of shifting 10kg of battery from out in front of the front axle to behind the rear axle was to try and get a bit more weight over the back of the car.

    I've now achieved that more permanently with a Cordoba (Ibiza with a boot). I can remember back to the 80's when people said the Jetta Mk2 was the better handling car than the Golf Mk2. Ok , it was slower 0 - 60, but courtesy of the boot at the back putting some weight on the back wheels it was a lot sweeter handling through the twisty stuff.
    Last edited: Jan 21, 2011
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  20. Audi2ptzero
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    Audi2ptzero Member

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    I understand that, I too have my battery relocated in my trunk of my A4 1.8t. But since I drag race and my trunk is not sealed from me I had to put it into a sealed box with a switch mounted outside the car to turn it off. If the trunk is sealed off from the driver then there really isn't a reason to put the battery in a sealed box.
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  21. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator

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    I've been thinking about this myself. Spare wheel well is obviously the sensible place to fit it, gets some weight over the back of the car, and keeps it out of the way, however 5 meters of heavy copper cable probably goes some way to negate the improvements.

    I'm thinking a compromise of behind the passenger seat with thinner cable. The stock cable is nowhere near 50mm. Its 16mm. I've run 25mm (3AWG) cable for my amp, and its huge compared with the starter feed.
    On a standard car theres a 16mm feed from the battery direct to the starter, then a 10mm feed from the battery to the central electrics panel under the dash.
    I think i'll probably run 25mm from the battery to the central electrics panel in the dash, then use the standard 16mm starter cable rerouted inside the car and connected to the 25mm at central electrics, assuming ofcourse that it will reach!

    Obviously the wiring layout in an A4 is a bit different, and i wouldnt recommend skimping on cable thickness on a full fat road car, but for a track toy, it will be fine. If your going to the boot, then perhaps 35mm would be an option to reduce voltage drop while cranking.
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  22. doublem_1
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    doublem_1 Member

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    A mate did this to his mk2 golf. Used a battery cable off of a BMW 3 series.
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  23. Pat
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    Pat Member

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    i have mounted mine in the back.. due to having issues with underbonnet temps..
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  24. MUSH
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    MUSH MUSH Developments Ltd.

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    I did this in my mk2 golf, i got the cable, terminals, mega fuse, and holder from vehiclewiringproducts.co.uk

    I used 40mm2 cable, never had any problems starting or charging, and that was 1.8t. The battery box was from some rover that i found on ebay. I modded it but it but it was spot on.

    Im tempted to do this on the S3 but mounting the battery in the tiny boot could prove to be a challenge...
    Last edited: Nov 6, 2011
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