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Trunk Mounted Battery Fuse

  • Thread starter Thread starter RangerJoe
  • Start date Start date May 8, 2011

RangerJoe

I leave the horn on while driving
15 Year Member
Apr 26, 2010
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May 8, 2011
#1
  • May 8, 2011
  • #1
First off, I know some people will disagree in doing it this way and say that there is a better, "correct" way to do this. However, I thought I would post this for those who are interested. If you don't like it or trust it, don't do it to your car

About five months ago I put my battery in the hatch, directly behind the passenger's seat. At the same time I hid my wires under the fenders, along with my solenoid. I routed my 1 guage cable under the rear seat, along my rocker panel under the carpet and through the firewall to the solenoid under the fender. The solenoid under the fender and the long 1 guage wire has made me nervous for fear of it shorting out or the solenoid being struck during a minor fender bender and causing it to short to the body. Basically, I didn't want a small wreck to turn into a fireworks show!

I have searched the internet over and over again looking at posts on this. It is discussed, but I could not find anyone who had actually done it, or described it in detail. My biggest concern was the amperage draw by the starter and the size fuse needed.

Internet research revealed amperage rating in a range of 225-275 amps for a 1 guage wire. I could not find what the actual starter draws (I have a 93 style starter, mini I believe). Then I thought about the actual starter wire, it is only a 4 guage wire, so it stood to reason that it would not pull anywhere near the 225-275 amps. I purchased an inline fuse holder and 300 amp ANL fuse and installed them on the rear of my battery box. The fuse holder is hidden by the rear seat. So far, it has worked great. I even disconnected the coil and let the starter turn over for about 5 or 6 seconds and the fuse held. I feel much more confident knowing that if it were to ground out, then the power would be cut.

Just thought I would post this incase anyone out there was searching or thinking about doing it too. Like I said, if you do not feel comfortable with this, then don't do it!
 

Mustang5L5

That is…until I whipped out my Bissell
Mod Dude
Feb 18, 2001
43,215
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Massachusetts
May 8, 2011
#2
  • May 8, 2011
  • #2
Why a 300a fuse?

If the wire rating is 225-275a, you want to fuse UNDER that. Otherwise, if something shorts and draws, say 280a, the wire will heat up and potentially melt or cause fire and fuse will never go.

You want the fuse to be the first thing to pop, so the rating should be the least of all the components in the loop. You really want to protect the wires in this case.

A smaller amp fuse might be a good idea, but need to take into account wire run size and heat the wiring will see.
 

2000xp8

SN Certified Technician
Aug 8, 2003
8,016
1,613
194
NJ
May 8, 2011
#3
  • May 8, 2011
  • #3
Mustang5L5 said:
Why a 300a fuse?

If the wire rating is 225-275a, you want to fuse UNDER that. Otherwise, if something shorts and draws, say 280a, the wire will heat up and potentially melt or cause fire and fuse will never go.

You want the fuse to be the first thing to pop, so the rating should be the least of all the components in the loop. You really want to protect the wires in this case.

A smaller amp fuse might be a good idea, but need to take into account wire run size and heat the wiring will see.
Click to expand...

Exactly.
If the fuse can't protect the wire, essentially it can't protect anything.
 

RangerJoe

I leave the horn on while driving
15 Year Member
Apr 26, 2010
2,560
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May 8, 2011
#4
  • May 8, 2011
  • #4
Honestly, a 300 amp is what came with my fuse holder. As far as the rating yall are recommending, yall are probably right. I will try to track one down sometime in the near future. That being said, I bought my car with a 3g upgrade, the 4 gauge wire was fused with a 200 amp (too big). I grounded the post on the back of the alternator with my ratchet while changing spark plugs. The fuse blew almost immediately. I checked the wiring and it was still good. I replaced with a 150 amp. This experience is what made me not worry too much about the extra 25 amps or so of fuse. But, like stated above, a smaller fuse is probably a good idea.
 

84Ttop

They make new pistons every day, so why worry?
5 Year Member
Jul 2, 2009
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May 8, 2011
#5
  • May 8, 2011
  • #5
why cant you take an amp meter, clip it around the starter wire and have someone crank the car? this is a sure fire way to tell exactly how many amps your starter is drawing. Then you can purchase an appropriate fuse as I do believe that 300 is way over shooting. just my 2 cents
 

Mustang5L5

That is…until I whipped out my Bissell
Mod Dude
Feb 18, 2001
43,215
17,898
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Massachusetts
May 8, 2011
#6
  • May 8, 2011
  • #6
84t-top said:
why cant you take an amp meter, clip it around the starter wire and have someone crank the car?
Click to expand...

I'm not aware of any non-contact clamp meters that can do DC voltage. If there are any, I'd be interested in buying one as I've been looking for some time.

The meters I see that do dc voltage need to be wired in series, and have a max of 10A
 

84Ttop

They make new pistons every day, so why worry?
5 Year Member
Jul 2, 2009
5,222
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May 8, 2011
#7
  • May 8, 2011
  • #7
Mustang5L5 said:
I'm not aware of any non-contact clamp meters that can do DC voltage. If there are any, I'd be interested in buying one as I've been looking for some time.

The meters I see that do dc voltage need to be wired in series, and have a max of 10A
Click to expand...

good question. you know i'm going to have to go out to the garage and look at my meter now.
 

Mustang5L5

That is…until I whipped out my Bissell
Mod Dude
Feb 18, 2001
43,215
17,898
224
Massachusetts
May 8, 2011
#8
  • May 8, 2011
  • #8
84t-top said:
good question. you know i'm going to have to go out to the garage and look at my meter now.
Click to expand...

I did some Internet searching. Seems they do exist...just are not common.

Greenlee CM-900 and CM-950 will do it to 600A. Megger DCM340 will also do 600A DC

I gotta get one now as I want a non-contact dc amp meter
 

HISSIN50

"How long does it take to get help in here?
15 Year Member
Nov 29, 1999
31,179
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May 8, 2011
#9
  • May 8, 2011
  • #9
A resettable circuit breaker is another option. It allows one to use it like a battery disconnect as well.
 
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