I need help determining fuse size for my battery relocation. (to trunk, with sealed NHRA legal battery box)

All the charts I see are using Amps or Watts - I'm not sure on those numbers for my system. Am I going to have to hook everything up and then do measuring with a multimeter?

From my battery to the starter is 8-9 feet long.

From my battery to the fuse box is about 5 feet long.

I would like to fuse both of these leads - just not sure exactly what size to use.

All the wiring is 2 gauge.

 

If you are using 2ga cable the fuse should be no bigger the 225A, max current capacity of 2ga cable.

A few questions...

1- MM&Y of car?
2- Where is batt. being located to?
3- The fuse box has a main fuse, why are you installing one to it?
4- How are you wiring the relocated batt., [from batt. the where]? 94

 

1993 Civic.

Battery is being relocated to the trunk ---- underhood fuse box has been relocated to underneath the dashboard because of engine bay wire tuck.

I'm installing a fuse because I have 9 feet of live power wire running under my carpet - I would rather be safe than sorry.

Not sure of your last question - From the battery I'm going straight to the fuse box. From the battery I am also going straight to the starter. Both are 2gauge leads. Some people suggested using 00 gauge cable and running a splitter. I don't have the money or the space to do that.

I'm more concerned with what the LOWEST rated fuse I should use is. I want to be as safe as possible.

Do you know a formula I could use?

 

OIC, then I would run the 2ga from the batt., [with fuse as close to batt. as possible] directly to the starter motor, then run an 8ga, [W/100A fuse as close to starter motor as possible] from starter motor to fuse box.

The fuses you install are for the cable you are using and you should always install as "big" a fuse as the current capability of the cable, if there is a problem, [short] the fuse will blow before the cable gets hot enough to become a problem.

The fuse on the line from the starter motor to the fuse box is there because the gauge of cable is smaller, [8ga] you do not need a 2ga to the fuse box, if you stick with a 2ga from the starter motor to the fuse box, you will not need a fuse between the starter motor and the fuse box.

Keep in mind, the less connections you have to make the better, that is why I would never recommend a splitter, it just adds connections, the starter motor is a perfectly good splitter, [daisy chain] and the starter motor should be connected directly to the batt., [just like stock].

I would also upgrade the alt. to fuse box "charge" lead from stock, [as you will have to replace it anyway] to an 8ga, and install a 100A fuse, [because you are going through the firewall with the lead] as close to alt. as possible.

You can also just run the alt. lead to the starter motor and install a fuse close to the starter motor, this fuse should be the same size as the main fuse in the fuse box.

I have done all the above more then a few times without any problems at all. 94

 

Okay, so for my 2 gauge lead from the battery to the starter, what size fuse should I use? 225 amp? Could I use a 200amp from like a car stereo setup? I'm having a hard time finding a 225 amp with an adequate fuse holder to fit my need.

That's a cool trick about the daisy chain.

Why would I not need a fuse between the battery and the fuse box? In the stock configuration, the lead between these two is only about 4" long. It will now be 5' feet long - I don't understand why I wouldn't want to fuse it near the battery?

You certainly understand more about the theory of current/capacities etc. but I'm just not entirely grasping it.

Thanks for the help.


Modified by Jonathan_ED3 at 7:59 PM 10/19/2008

 

Yes you can use a 200A.

If you run the batt. lead to the fuse box from the starter motor it will have a fuse, [200A by the batt.] if you use a smaller gauge lead from the starter motor to the fuse box then the 2ga you are running from the batt. to the starter motor, [8ga is what I suggest] then you will need a fuse, [as I mentioned].

Remember, the fuses are there to "protect" the wire/cable, if you install a fuse at the batt. all wiring after the fuse is protected, if at any point the wire gauge gets smaller a proper fuse for the smaller gauge wire is needed, in your case, [as I recommend] you will be running a 2ga power cable from the batt. to the starter motor with a 200A fuse as close to the batt. as possible/convenient, that fuse protects that 2ga power cable, if you then run another 2ga from the starter to the fuse box, the 200A fuse will protect that cable also, if on the other hand you step down the gauge to an 8ga lead between the starter and the fuse box, [or even a 6ga or 4ga] a fuse needs to be installed as close to the starter motor, [end of 2ga] as possible to protect the smaller gauge cable. 94

 

quick question

im using a 2 wire fuse holder under the hood with the battery in the trunk, the fust for the starter keeps blowing im asuming its because I had a 60 amp fuse in their, what would you recomend for the starter fuse. thanx guys

 

Are you trying to fuse the starter wire from the key (black/white) to the solenoid, or the main feed from the battery to the starter motor? The 200A fuse between the battery and the system is good for the electrical system, but most starter motors are capable of drawing more than 200A.

Most vehicles will fuse the starter/solenoid lead, but the starter main feed is directly off the battery w/o a fuse. You could however install a 200-300A circuit breaker between the battery and the starter, circuit breakers can take nearly double the rated amps before poping, and they are much easier to reset than a fuse is to replace.

Kirk R

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by GDM Phil &raquo;</TD></TR><TR><TD CLASS="quote">quick question

im using a under the hood with the battery in the trunk, the fust for the starter keeps blowing im asuming its because I had a 60 amp fuse in their, what would you recomend for the starter fuse. thanx guys</TD></TR></TABLE> As suggested above, get rid of the "2 wire fuse holder " connect the batt. lead directly to the starter motor and run a lead from the starter motor to the under dash fuse box, it will solve your problem and eliminate quite a few connection points. 94