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Re: Battery in the boot
[Re: ]
#1197465
06/04/2011 17:44
06/04/2011 17:44
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Marco20valveT
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Marco20valveT
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giggady.. Neil, i may call you as i have a wiring idea!! ![laugh laugh](/forum/images/graemlins/default/laugh.gif)
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Re: Battery in the boot
[Re: ]
#1197571
06/04/2011 21:37
06/04/2011 21:37
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Joined: Dec 2005
Posts: 33,655 Berlin
barnacle
Club Member 18 - ex-Minister without Portfolio
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Club Member 18 - ex-Minister without Portfolio
Forum Demigod
Joined: Dec 2005
Posts: 33,655
Berlin
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Wherever the battery is in the car, all the current that flows *out* of it also has to flow back *into* it - conventionally we think of current as flowing from the positive to the negative terminal. The significant current draw is during starting; this can be several hundred amps. If the cable is not rated for that current, it will get hot and potentially melt its sheath; that leads to a short circuit to a convenient earth (usually the chassis) and that leads to massive currents, massive heat, and fire - because the lead acid cell has a very low internal resistance. So, the positive wire has to be fat enough to pass the necessary current without heating. The negative wire returns usually through the chassis, but has to connect to it somewhere - that wire has to carry the same current as the positive, so it should be as thick... Neil sorry for my ignorance, but you mean that the earth cable that you need to use is the same one? So, yes... btw - the alternator can supply well over 100A on aircon models, so after a few seconds of very high current starting, there could be several minutes of high current going the other way to charge the battery. However, most high currents on the positive side - alternator to aircon, fan, and lights, circulate to the main fuse box which remains at the front of the car. It's really only starting and charging currents which are of concern here. (A secondary effect is the voltage drop across the resistance of the wire. You want that as low as possible, hence as thick a wire as possible. On my kit I have to run both the positive and negative from the back to the front since I have no chassis to carry the ground; the fiat wiring shows many earths but they all expect to pick up an earth from the chassis - that is, they're providing an earth path *to* the chassis from the various lights and whathaveyous. The chassis is clamped very close to the battery on the coupe loom and can be considered to be a very low impedance path back to the battery.)
Last edited by barnacle; 06/04/2011 21:38.
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Re: Battery in the boot
[Re: ]
#1197755
07/04/2011 01:28
07/04/2011 01:28
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Per
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Per
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I have only the pos.cable to the front, absolutely no problems at all. Saves weight too.
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Re: Battery in the boot
[Re: ]
#1220289
27/05/2011 07:54
27/05/2011 07:54
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NineOneSix
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NineOneSix
Unregistered
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See if you can get the wire from a gtv breaker as they have it back there as standard and possibly workout cheaper then buying new and having to get new terminals etc etc.
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Re: Battery in the boot
[Re: crgracing]
#1220379
27/05/2011 12:20
27/05/2011 12:20
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Joined: Dec 2007
Posts: 2,252 Windsor/ Reading
knight7660
Competition Level
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Competition Level
Joined: Dec 2007
Posts: 2,252
Windsor/ Reading
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I was thinking of doing the same but, ive been reading that for LHD cars it dosen´t make much difference on handling, is that true?
If it is, i just can`t understand why?. im going to be doing the same to my coupe but i think the most advantage is the mount of space it frees up in the engine bay which im after more than anything
LE53 (452BHp & 389ftlb's with Quaife) Wine red VIS FOOFY Audi RS4 B7
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Re: Battery in the boot
[Re: ]
#1225271
09/06/2011 16:15
09/06/2011 16:15
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Apogee
Unregistered
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Apogee
Unregistered
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Be aware that if you move the battery to the rear of the car, you will get a larger voltage drop due to the internal resistance of the copper cable being over a longer run. In other words, copper cable will drop x volts per metre due to its internal resistance. The longer the cable the greater the voltage drop. I would suggest a thicker cable be used for your new cable run to the battery in the rear than you currently have in the front. Have a look at this site www.stealth316.com/2-wire-resistance.htm to see what your V drop is for a given length and diameter cable. All this means is that you will get the amps you need to turn your starter motor properly and the fatter cable will reduce the build up of heat in the cable and hence less risk of a melted sheath or worse still ... fire. I am in the process of doing the exact same thing in my Stag Cheers
Last edited by Apogee; 09/06/2011 16:16.
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Re: Battery in the boot
[Re: ]
#1225331
09/06/2011 18:36
09/06/2011 18:36
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Nixa
Unregistered
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Nixa
Unregistered
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Be aware that if you move the battery to the rear of the car, you will get a larger voltage drop due to the internal resistance of the copper cable being over a longer run. In other words, copper cable will drop x volts per metre due to its internal resistance. The longer the cable the greater the voltage drop. I would suggest a thicker cable be used for your new cable run to the battery in the rear than you currently have in the front. Have a look at this site www.stealth316.com/2-wire-resistance.htm to see what your V drop is for a given length and diameter cable. All this means is that you will get the amps you need to turn your starter motor properly and the fatter cable will reduce the build up of heat in the cable and hence less risk of a melted sheath or worse still ... fire. I am in the process of doing the exact same thing in my Stag Cheers you dont have to make calculations you put a cable from an alfa 164 that has the battery in the boot no problems or calculations its been done in alfas from factory
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Re: Battery in the boot
[Re: ]
#1225347
09/06/2011 19:40
09/06/2011 19:40
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Tazz2732
Unregistered
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Tazz2732
Unregistered
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I tried starting my coupe with a battery in the boot running through an amp cable, wouldn't even kick, with a new battery. So leave the amp cables alone in my opinion
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Re: Battery in the boot
[Re: ]
#1225532
10/06/2011 03:12
10/06/2011 03:12
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Apogee
Unregistered
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Apogee
Unregistered
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The point I was making was that you will need larger diameter cable to the battery in the back than what you may already have to the battery in the front due to higher resistance in the copper cables. What is an amplifier cable going to do unless it is a fatter cable?
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Re: Battery in the boot
[Re: ]
#1233024
01/07/2011 14:21
01/07/2011 14:21
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santa09
Unregistered
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santa09
Unregistered
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This would also make it easy to run a seperate power to the fuel pump, like 2 birds with one stone this one! Well maybe 3 or 4 actualy.. Weight distribution Engine bay access Fuel pump mod ....... ![smile smile](/forum/images/graemlins/default/smile.gif)
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Re: Battery in the boot
[Re: ]
#1233784
04/07/2011 00:11
04/07/2011 00:11
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Per
Unregistered
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Per
Unregistered
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This would also make it easy to run a seperate power to the fuel pump, like 2 birds with one stone this one! Well maybe 3 or 4 actualy.. Weight distribution Engine bay access Fuel pump mod ....... Yepp! ![smile smile](/forum/images/graemlins/default/smile.gif)
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Re: Battery in the boot
[Re: ]
#1234127
04/07/2011 22:24
04/07/2011 22:24
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Joined: Dec 2006
Posts: 1,360 stockport
volumex
My job on the forum
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My job on the forum
Joined: Dec 2006
Posts: 1,360
stockport
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just going through this thread i have done what is wanted here after lots of testing ... i use a red top battery which is a gel and sealed so it can be put in any position i know its not on a coupe that i have fitted the battery to but i know it works with no problems 1 get the thickest battery cable you can within reason if you have aircon the bigger the better 2 with a red top you could mount the battery on the bulkhead behind the back seats as high as you can or behind the side fittings (carpet) 3 this is the big one put in a earth cable to the body in the boot and you most run a earth cable from the battery to the engine. i dont care what people say the earth works .... i get better cranking with the earth every time this is what i have done on my bro's celica st185 track car http://i1129.photobucket.com/albums/m508/louieuk/st185/P1080003.jpghttp://i1129.photobucket.com/albums/m508/louieuk/st185/P1080005.jpg
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Re: Battery in the boot
[Re: ]
#1234276
05/07/2011 11:17
05/07/2011 11:17
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Per
Unregistered
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Per
Unregistered
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One other benefit is of course you can put the battery much lower than std position; in the sparewell. So I disagree with putting the battery high up and the need of a thick heavy long earth cable.
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Re: Battery in the boot
[Re: ]
#1416508
18/03/2013 00:34
18/03/2013 00:34
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joe_yong
Unregistered
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joe_yong
Unregistered
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Hi guys, any follow up on this mods? Curious, what model of battery do you guys use? The stock in Malaysia is Din55, but some mechanic recommends Din66. do you use the same calling name? Thanks
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