what in-line fuse to run between battery and alternator..

[Dylan JZ]

long story short and despite the safety issues (looking to rectify that btw), my car has always had the main battery cable from the hatch (relocated at time of swap) connected directly to the alternator.

I have a 100amp SC300 alternator on my 1J, and the wire to and from is 00awg IIRC. What fuse should I be looking at for safety reasons?


Some one suggested this on another forum for MKII Celicas: http://www.westmarine.com/webapp/wc...1&storeId=11151&partNumber=10093821&langId=-1

with the actual fuse (various selections here): http://www.westmarine.com/webapp/wc...151_10001_17364_-1____ProductDisplayErrorView


Is this overkill?> I want it to be safe, but I was thinking that $65 may be indicative of going too far. On the opposite end, maybe that's exactly what I need. Please let me know your thoughts.

 

[TweakTech]

Almost all Toyotas have a factory 100A fuse between battery positive and the alternator. 100A should be more than enough

 

[Dylan JZ]

Thanks, I was wondering if the 100 or 130A was the right choice, guess I'll go for the 100.

 

[Supracentral]

This chart might help to determine if the wire you're using is heavy enough to carry 100A.

 

[Dylan JZ]

well, I'd say the wire is plenty big (gauge wise) according to that table. thanks, Mike.

 

[Supracentral]

well, I'd say the wire is plenty big (gauge wise) according to that table. thanks, Mike.

Just wanted to be sure. A 100A fuse isn't worth a lot if your wire will turn into glowing metal at 50A.

 

[Dylan JZ]

Oh, that's for damn sure. After studying that table however, is there a downside to running too large a cable?

It would appear 00awg is enough for more than double 100amps.

 

[Supracentral]

There's no downside to larger wire other than the cost and it's generally harder to route/work with. Think of an oversized wire like an uncrowded highway.

Also, place the fuse as close to the power source as possible.

 

[Dylan JZ]

Will do. I'll mount the fuse right on the outside of the battery box (easy access, in plain sight, and close to the power source).

Thanks again, this all helped a great deal!

 

[Dylan JZ]

I just wanted to update this by saying that I went for a 150amp 12v breaker box instead of a fuse.. this way, if it kicks the breaker for any reason, I do not have to put in/buy a new fuse, and oddly enough it is cheaper and easier to mount despite seemingly being the better option (I'm used to the better option always being more expensive).

Anyhow, I'm running a 100amp SC300 alternator on the 1J, battery in the trunk with 0/1 AWG (not 00) running direct to the alternator, so I figured 150amp should be a plenty good enough safety measure. Some folks go even higher to like 200amps with smaller wire...


Maybe this info will help someone out sometime.

 

[ifyouaint1sturlast]

Mike, couldn't running too large a gauge wire increase resistance? Like using a fire hose for a garden hose job.. wouldn't the signal be weaker at the end due to it having to distribute itself through the "extra" conductors?

 

[jetjock]

^ No. In fact the opposite is true.

 

[ifyouaint1sturlast]

Any downside to a larger wire than necessary ?

 

[CyFi6]

Any downside to a larger wire than necessary ?

Weight, cost, availability of space.

 

[ifyouaint1sturlast]

Sorry for not being clear. I just meant for the application itself, would there be a downside. I'm all about learning and my Google search didn't turn up anything from sources I particularly trust (Wikipedia)

 

[GrimJack]

No, CiFi6 has listed all the possible downsides.

 

[CyFi6]

Sorry for not being clear. I just meant for the application itself, would there be a downside. I'm all about learning and my Google search didn't turn up anything from sources I particularly trust (Wikipedia)

You could use an 80mm^2 wire for an ECU signal wire sending millivolts and it would have no adverse affects on the signal. I understand your thinking, but literally bigger is always better as far as conductivity goes.

 

[te72]

So many myths dispelled all in one thread, I like it! Will likely come in handy once we move the battery (and possibly fuse box) into the rear seat area... may end up rewiring the whole damned car while we're at it.

 

[Dylan JZ]

I'm glad this thread took off and ended up with some good info..

 

[Supracentral]

You could use an 80mm^2 wire for an ECU signal wire sending millivolts and it would have no adverse affects on the signal. I understand your thinking, but literally bigger is always better as far as conductivity goes.

100% correct.