Best size fuse for battery relocation?
 

Hey all, I relocated my battery into the rear of my crx using 2g wire for both the positive and the negative. I ran a regular "non sealed" battery inside a battery box. after sitting in storage for quite a while the past couple years, the battery is finally toast. So I purchased an optima yellow top.

I was doing a little research and realized that I never installed an inline fuse on the positive battery cable. So upon installing my new battery, I installed an inline fuse holder with a 60 amp fuse, but of course only being 60 amps, the fuse popped right before my car fired up.

I have a B20 swap. Ive been searching online, some people say that an 80 amp fuse is enough, others say that a 225 amp fuse is what should be used. I just can't find any consistent answers.

I fear I will need to get an entire new fuse holder. it is meant for 4g cable, oddly enough the 2g fit in nice and snug. But the biggest fuse I can find for this style of holder is 100 amps. "AGU style fuse"

this is one similar to mine

http://www.ebay.com/itm/FUSE-HOLDER-WITH-AGU-2-40-AMP-FUSES-4-8-10-GAUGE-PS88-/110765017281?pt=US_Car_Audio_Video_Fuses_Fuse_Holders&hash=item19ca1c08c1
I've seen another style of fuse holder that allows a bigger fuse, but im not sure if that's necessary. But now I'm a little concerned with mine considering its meant for 4-8g cable and mines 2g. And there aren't many better fuses I could put in it.

Re: Best size fuse for battery relocation?
 

get one of the high amperage circuit breakers, I think mine is buss, that way if you pop the breaker,say trying to start the car in cold weather, it's a simple pushbutton reset. remember fuse for the wire size, not the circuit in this case. you are protecting the battery lead, not individual circuits. also unless it's a completely sealed battery like an AGM, you still have outgassing and a chance of explosion, so the box needs to be sealed and vented outside the car, it also needs to be a metal box, bolted through the body, with a doubler plate underneath. on any hatchback, the battery is INSIDE the car, so treat it like it's right next to you. Battery explosions are not pretty

Re: Best size fuse for battery relocation?
 

Any idea how many amps is considered a "high amperage circuit breaker"? maybe 250 amps? I was led to believe that the optima batteries are sealed.

Re: Best size fuse for battery relocation?
 

The max fuse size you can get will depend on the type of wire you bought. 2awg sure as hell isn't rated for 250A, you would have to go up to 90 deg C 4/0 for that many amps.

What type of wire did you use?

Re: Best size fuse for battery relocation?
 

I just know its 2 gauge battery cable.

Re: Best size fuse for battery relocation?
 

how about a 100 amp or 150?

Re: Best size fuse for battery relocation?
 

Is it Aluminum or Copper wire? If it's copper the max I would go is 100A fuse, if it's aluminum then the max I would go is 75A fuse. Since I can't see what type of wire it is, then any larger fuses would risk making your wire or connections the fusible link rather than the fuse itself. This is of course prolonged amp draw, in case something was grounding out but still enough resistance to not blow a fuse.

Re: Best size fuse for battery relocation?
 

It is copper cable

Re: Best size fuse for battery relocation?
 

how about RESEARCH google for the ACTUAL math for length of feet vs amp draw?????


as you go longer in battery cables your amps WILL increase (due to higher resistance).

there is math formula for it.

Re: Best size fuse for battery relocation?
 

Yep, amp draw will increase to do the same amount of work with longer cables, and the equation is only 3 variables :P

Basically you need to know how many amps the starter will draw, factor in cable length, and size wire and fuse appropriately. I take back the 100A limit, with the starter, since it is short durations you can go up2 a 120A fuse. If you pop a 120A fuse, then I recommend bigger wire before putting in a larger fuse.

Re: Best size fuse for battery relocation?
 

The main battery positive should be unfused, as the current requirements by the starter will change with engine temperature. You should be using two wires, one for the fuse panel (which is already fused), and one for the starter, which is unfused.

Make sure the cable you use is the right size given the length and current requirements. There are many charts on the web that stereo installers use to estimate cable size. Make sure the insulation is very strong, and the cables are routed to prevent rubbing and damage to the insulation.

If you pop a 120A fuse, increasing the cable size will only ensure it pops again.

No automotive starting circuit is fused between the battery and the starter.

Re: Best size fuse for battery relocation?
 

you are putting a battery in the back of a car with a battery cable running all the way through the car, the battery needs to be fused as close to the battery as possible, if you dont think it should be, you are an idiot, or have never seen how fast a car can catch fire from a shorted battery cable, they aren't fused in most cars,because the battery cable to the starter is only a couple of feet at most, and is all behind the firewall. There is a reason It's called a firewall. if you can't start a little 4 cylinder engine with a 2 gauge battery cable, something is wrong. even in cold weather. These are all geared starters, they dont pull nearly as much current as a standard starter. I would be surprised if they pull much more then a four cylinder touring bike. as far as power to the fuse block, a properly insulated copper tap can be used before the cable exists the car, you don't need a second wire. Or look around at the junkyards, and you can often find firewall mounted terminal blocks

Re: Best size fuse for battery relocation?
 

Here is the littlefuse 100 amp breaker, they come in different amperage's, this will protect your car against a battery cable short, and is pushbutton reset, you can also disconnect the battery by pushing the button. This should be able to handle that starter in the crx under most conditions, edit the D series starter draws maby 80 amps, so the 125 amp breaker would be fine. be careful of the cables you are using, some of the stereo cables people sell, aren't pure copper, and actually have a lot lower rating for their gauge, then a cable that is all copper. Good cable is not cheap, copper is expensive

http://www.primelec.com/media/catalo...2-005-pic1.jpg

Re: Best size fuse for battery relocation?
 

so it turns out my positive cable is a 4 gauge and my negative is a 2 gauge. I assumed they were the same when I checked the size on the negative. Im thinking of mounting it in the storage compartment in my crx, hopefully eliminating a few feet of wire. but I tried a 100 amp fuse today and no luck

Re: Best size fuse for battery relocation?
 

http://www.summitracing.com/parts/sum-g1231-k/overview/

thinking about getting this kit, seems a little overpriced though.

Re: Best size fuse for battery relocation?
 

does it matter what size of cable you use on that breaker?

Re: Best size fuse for battery relocation?
 

the fuse or breaker size depends on the capacity of the wire used,not the other way around. you are saying you blew a 100 amp fuse when you tried to start the crx? thats strange, a lot of people start their race ones with lawn and garden batteries, you shouldnt be blowing that fuse, it's possible the four gauge wire could have something to do with it

Re: Best size fuse for battery relocation?
 

thats actually not that bad, that box is just like the morosso box, and considering the kit uses high quality 1 gauge wire, thats a pretty good price. copper price is outrageous right now, the price of these kits goes up and down a lot depending on it's price. make sure when you attach your ground to the car body, it's a solid connection to bare metal. after the connection is made, you can coat it with petroleum jelly, to prevent corrosion

Re: Best size fuse for battery relocation?
 

i also noticed my positive cable is connected halfway with a butt connector. could that be bad?

Re: Best size fuse for battery relocation?
 

what if i didnt have enough ground wires? i believe im missing one that goes to the transmission. could that have something to do with this?

I think im just going to pull the trigger and get this kit and do it right.

Re: Best size fuse for battery relocation?
 

you can always add more grounds under the hood later, the ground from the battery to the car body is the main one to make sure is right with this kit.

Re: Best size fuse for battery relocation?
 

If it was not properly crimped, then that will be a failing point in the future. That's typically where corrosion starts and is a shitty way to do it. Also I would only run a maximum of 80A fuse with 4awg, WITHOUT that stupid ass splice. You need bigger wire.

Re: Best size fuse for battery relocation?
 

Also since it's the starter we are talking about, are you missing the ground wire from the frame to the tranny? If so, that is one less path back to the battery, I would advise getting that back on ASAP. And if you have to do a new one, bigger is better.

Re: Best size fuse for battery relocation?
 

alright im gonna go with the summit kit with the 1 gauge cable. what size of fuse or breaker should i be using ?

Re: Best size fuse for battery relocation?
 

You would be safe with 130A breaker/fuse for 1awg