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The mkiv Supra Owners Club

What amp is the starter cable?


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Mate you need to use zero gauge cable. The alternator pulls almost 300 amps which is why I said get a 300 amp fuse. Run 4 gauge from the fusebox to the distribution block and iluse the stock cable from the started to the block also. Then run zero gauge to the back.

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Mate you need to use zero gauge cable. The alternator pulls almost 300 amps which is why I said get a 300 amp fuse. Run 4 gauge from the fusebox to the distribution block and iluse the stock cable from the started to the block also. Then run zero gauge to the back.

 

Is that definitely right John? I thought the Alternator fuse is 120A and that the output of the stock alternator is 90A (might even be less as that might be Auto).

 

Certainly never heard of anything anywhere near 300 mentioned.

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Is that definitely right John? I thought the Alternator fuse is 120A and that the output of the stock alternator is 90A (might even be less as that might be Auto).

 

Certainly never heard of anything anywhere near 300 mentioned.

 

Think he may have meant for the starter motor, most small engined cars need around 200A to get started, would think the supra may need ~300A. Diesel are even worse with the higher compression they may even take upto 600A. Hence why cold cranking capacity of batteries are normally between 300-750A.

 

Ages ago I had zero guage cable jump leads 3m long and when trying to start a difficult engine (not a supra but a large cc engine) managed to get them so hot (10 attempts, 5 secs crank) they melted the plastic. There is a reason the battery is mounted in the engine bay as close as possibly to the starter motor.

 

If using 0 Guage its only rated to 150A so as long as its protected by a ~150A (hence why main fuse is 120A on a supra, although main positive to starter may be unfused because its a short run) fuse you will be ok. Personally I would run thicker than 0 guage as long cranking could cause overheating/fire issues if you intend to relocate the battery to the boot.

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Think he may have meant for the starter motor, most small engined cars need around 200A to get started, would think the supra may need ~300A. Diesel are even worse with the higher compression they may even take upto 600A. Hence why cold cranking capacity of batteries are normally between 300-750A.

 

Ages ago I had zero guage cable jump leads 3m long and when trying to start a difficult engine (not a supra but a large cc engine) managed to get them so hot (10 attempts, 5 secs crank) they melted the plastic. There is a reason the battery is mounted in the engine bay as close as possibly to the starter motor.

 

If using 0 Guage its only rated to 150A so as long as its protected by a ~150A (hence why main fuse is 120A on a supra, although main positive to starter may be unfused because its a short run) fuse you will be ok. Personally I would run thicker than 0 guage as long cranking could cause overheating/fire issues if you intend to relocate the battery to the boot.

 

 

Yeah, I can understand that. I wouldn't be using 0gauge for a starter personally. It needs proper density core cable.

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Yeah, I can understand that. I wouldn't be using 0gauge for a starter personally. It needs proper density core cable.

 

Agreed, would only relocate the battery to the boot if I got an air start motor somewhat like mad max 2. Check out the sound they make its awesome!

 

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Positive to starter motor is usually unfused because the current can spike to huge figures way in excess of max current load rating of cable and a battery rated at say 750 without buckling it's plates can potentially deliver 1000's amps as the voltage drops on a long cable that's getting hot, so a pair of good quality high density low oxygen copper cables is important, unfortunately 12v doesn't carry along long cables so well

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Positive to starter motor is usually unfused because the current can spike to huge figures way in excess of max current load rating of cable and a battery rated at say 750 without buckling it's plates can potentially deliver 1000's amps as the voltage drops on a long cable that's getting hot, so a pair of good quality high density low oxygen copper cables is important, unfortunately 12v doesn't carry along long cables so well

 

Yeah, I knew the starter drew a fair whack... hence why we need the reasonably high level diesel batteries :D

 

The stock cable isn't that thick, probably 120A or something like that to cover the alternator, but the distance from the boot will be the clincher. I think that 170A stuff I linked to should be fine but I wouldn't fancy letting it crank for any major length of time. It's going to be the same regardless though unfortunately.

 

To the op, make sure the starter motor is good :D

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Yeah I ment the starter motor Scotty. As in cranking amps. I learnt the hard way only fusing it to 100 amps and it blew very quickly. I had to bridge the fuse with a nail to get me home.

I fitted a 250A after that, it didn't break but had distinct evidence of burning around the fuse wire. I've fitted 300A fuses on every battery relocation I've done since then. Mind you I've seen it done without being fused. It's madness as far as I'm concerned but I have seen it. You can't have enough safety devices where electric is concerned IMO.

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Yeah I ment the starter motor Scotty. As in cranking amps. I learnt the hard way only fusing it to 100 amps and it blew very quickly. I had to bridge the fuse with a nail to get me home.

I fitted a 250A after that, it didn't break but had distinct evidence of burning around the fuse wire. I've fitted 300A fuses on every battery relocation I've done since then. Mind you I've seen it done without being fused. It's madness as far as I'm concerned but I have seen it. You can't have enough safety devices where electric is concerned IMO.

 

Yeah it's a tough one with the boot install. So much length to take account of that it could melt in-between and cause a fire when touching the body.

 

I wouldn't recommend 0gauge though John, that sort of cable isn't really up to the task of a battery relocation IMO. We have cable in the work that's no thicker than 8 gauge and yet can easily cope with 600+ amps over a reasonable distance. The stuff doesn't flex well right enough :D

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We'll have to agree to disagree here Scotty. If fitted loads of these and never had issues.

The SRD battery relocation kit uses Zero gauge wire too and IIRC lee is an auto electrician.

 

Fair enough, I don't think any manufacturers use zero gauge for that area of a car though. I know it's the norm for audio but I would always use higher density for high loads.

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