rear mount batt - cable routing

John Dirks Jr

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I'm shopping for fuse and fuse holders for the main positive battery cable since I'm planning my rear mount battery in the 92 hatch. I like one of these two holders so far but not sure which one I'll go for. Do any of you have an opinion on these or maybe a suggestion for a different one? I'd always keep extra keep extra fuses on board. I'm thinking 200amp on the fuse size. Is that good for a stock compression, stock starter SBF Ford?

Blue Sea

Go Power < more expensive and fuses may be harder to get but I like the built in lugs to attach cable to

I have a Summit battery box (sealed type), #2 welding cable and the various parts for making good connections. I want to run the cable through the interior and out the firewall into the engine compartment. If I protect it properly it should be a really safe setup.

This pic below is what ill probably do, (the optional line) I'm thinking I'll come out the bottom edge of the battery box, go behind the rear side panel, under the rear seat, under the carpet (but above the padding) along the trans tunnel, exit the interior about half way up the firewall (nice grommet of sorts for sure) and into the engine compartment. Once in the engine compartment ill cross the firewall to the drivers side and tap the solenoid. Ive already got a massive alt cable like shown in the image below. Ive mocked it up and it looks fairly easy.

38E5FADE-A5FA-4CDB-A1E0-021C852DD3FF.png
 
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TOOLOW91

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That will work and is how I have mine minus the optional wire . Mine comes through the grommet for the cruise control cable and harness on the drivers firewall but in the fender .

My car shuts right off because my ecu is tied into my solid state switch as well as injector power so it all goes dead as soon as you hit the button

200 a is fine on the fuse .
 
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TOOLOW91

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Jeff, is your main + cable running through the interior, or under the car?
Inside . I am not a fan of under the car honestly . And I have 0/2 welding cable . Then 2awg from my alt to the circuit breaker then to the distribution stud . 2 awg from starter as well .

Stock solinoid is deleted and just uses a relay to hit the sol on the stock mini starter
 

John Dirks Jr

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Here's my chosen method of tapping at battery

IMG_4819.JPG


I'll come under the rear seat like this

IMG_4814.JPG


Along the tunnel, above the padding but under the carpet and up under dash here

IMG_4815.JPG


In critical areas needing extra protection, including passing through the firewall I'll use heater hose

IMG_4812.JPG
 

John Dirks Jr

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Yeah, I was questioning the #2 welding cable at first but then I checked how they rate it. That stuff is rated in really long runs, like 100' and greater. So, #2 awg welding cable was good to 200 amps on a 100' run. My run will be 15' so considerably less voltage drop potential there. #2 is plenty I think.
 

TOOLOW91

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That’ll work . I like overkill on the wire and beside that the 0/2 didn’t cost me anything so it worked out
 
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John Dirks Jr

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John Dirks Jr

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Here’s where I mapped the hole in firewall will be. Right where I drew the black circle.
3C254542-26AE-4ADF-873A-ECD0AA9508D9.jpeg
Just barely enough access to make a hole here working from the interior side under the dash.
 

TOOLOW91

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Here’s a welding cable rating chart. Note the length associated with the rating. Also note that any cables ability to dissipate heat can affect its rating. So, enclosing cable in conduit or having it exposed to an environment with excessive heat (like and engine compartment) can de-rate ampacity.

I still think #2 at a 15’ length is plenty for my application.

Absolutely
 

TOOLOW91

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Here’s where I mapped the hole in firewall will be. Right where I drew the black circle.
3C254542-26AE-4ADF-873A-ECD0AA9508D9.jpeg
Just barely enough access to make a hole here working from the interior side under the dash.
That’s not going to work unless you plan on drilling through the heater box . I don’t think you can get up that high .
 

John Dirks Jr

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Hmmm. It looked like a clear shot based on the lower heater box mounting bolt as viewed from both sides. I’ll double check.
 

TOOLOW91

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Hmmm. It looked like a clear shot based on the lower heater box mounting bolt as viewed from both sides. I’ll double check.
Pic may be decieving . I’d just come down the driver side though
 

John Dirks Jr

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Pic may be decieving . I’d just come down the driver side though
I'll let you know what I find when I look again. My thought (actually not my thought but I saw it discussed elsewhere) by running along trans tunnel was additional protection from side impact in a collision which might damage a cable running along the rocker panel. I'll be fused either way but who knows, I may wind up adopting your route in the end.
 

John Dirks Jr

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One thing for sure is my sub woofer cable will be alot shorter now. And I'm stealing the sub box out of the vert because it sounds so much better than the Infinity one I've been using in the hatch. One question about this big wide sub box you see in the picture. It's way heavier on the speaker side obviously. It will fit in either position. I know the battery on the passenger rear helps to balance weight distribution. Should I also put the heavier side of the sub over towards the passenger side along with the battery?

IMG_4802.JPG
 

John Dirks Jr

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To be NHRA track legal, you need a cut off switch.
Thanks for the info. I figured that might be the case but I don’t need this car to be NHRA legal so I didn’t bother researching it.

I figure a well routed fused main cable will make this car as safe as any other on the street, at least in terms of battery cable failure and problems it might cause.

It’s just a street car with a respectable amount of power that needs a little help in the traction department. I’m working on it :)
 

John Dirks Jr

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Is it ok to vent the battery box through the bottom of the box and straight through the trunk floor to the outside? Sealed with snug fitting vent tube of course. Or, should the vent in the battery box be near the top of the box?