Team Camaro Tech banner

LS Swap battery cable through firewall

12K views 51 replies 8 participants last post by  Shannon4570 
#1 ·
Anyone use a bulkhead connector for their pos battery cable going through the firewall ?? I was also considering just a grommet and run the cable to the starter. I'm not sure I like the idea of a live connection at the firewall, even if its only live during cranking. I hope the protective caps on the bulkhead connector would prevent any accidental contact.
 
#3 ·
Hey Donnie,
I am at that point too and have been trolling a lot trying to decide that. I am going to use a bulkhead connector. I think I am going to put it in the horizontal flat formed section of the passenger floor. What i am thinking over now is what bulkhead to use, i dont know that i like the one handled by summit but it will fit on that small flat. I am also thinking about a solid pass through connection for the negative cable. I intend to run negative to the block and am pondering the pros and cons of interrupting that cable. More bad chit happens when the system hunts for a decent ground than a decent hot.
 
#4 ·
Thanks guys. Don, no protective caps to prevent accidental contact ?? Steve, If your battery is in the trunk the ground should be as short as possible.
 
#5 ·
I run the posi cable underneath the car tight up to the frame rail and not through the passenger compartment. As mentioned it's only hot while cranking.

When i was planned and trying different routing I felt that running it through the wire chase then behind the kick and eventually through the firewall wasn't worth the effort.

I fixed your link. Lol
 
  • Like
Reactions: DT
#6 ·
"Only hot while cranking" are you running the solenoid in the boot? If not that positive cable is ALWAYS hot.

---Nitrous Fed 468ci Big Block and m21 69 SS Camaro---
---163kg/140rwhp K3 GSXR 1000---
---TD42 GU patrol ute 6inch lift blah blah blah---
---Stock as a rock 91 F77 Daihatsu Rocky Ute---
 
#9 ·
Battery in trunk. 12V bat cable to solenoid. Cable from solenoid to starter. 12v from ignition switch (start position) to solenoid trigger. separate fused wire from bat side of solenoid to fuse box power for the car.

The 12V cable from the solenoid to the starter is only hot while cranking.
 
  • Like
Reactions: DT
#10 ·
I understand that. But the solenoid is on the starter is it not? So the cable from the battery in the trunk that goes to the solenoid on the starter motor is live all the time and as you say the short cable from aolenoid to starter is only live while cranking. Or am i missing something.


---Nitrous Fed 468ci Big Block and m21 69 SS Camaro---
---163kg/140rwhp K3 GSXR 1000---
---TD42 GU patrol ute 6inch lift blah blah blah---
---Stock as a rock 91 F77 Daihatsu Rocky Ute---
 
#11 ·
I understand that. But the solenoid is on the starter is it not? So the cable from the battery in the trunk that goes to the solenoid on the starter motor is live all the time. Or am i missing something.


---Nitrous Fed 468ci Big Block and m21 69 SS Camaro---
---163kg/140rwhp K3 GSXR 1000---
---TD42 GU patrol ute 6inch lift blah blah blah---
---Stock as a rock 91 F77 Daihatsu Rocky Ute---
We install an additional Ford style solenoid in the trunk.

Auto part Automotive engine part Engine
 
#13 ·
Cant say ive ever done that. Every car i have owned ive run the main csble to starter from trunk live all the time along frame rails etc. Never had an issue with shorting or damage. Ive Always run double insulated cable though.

---Nitrous Fed 468ci Big Block and m21 69 SS Camaro---
---163kg/140rwhp K3 GSXR 1000---
---TD42 GU patrol ute 6inch lift blah blah blah---
---Stock as a rock 91 F77 Daihatsu Rocky Ute---
 
#18 ·
Good to know Steve, let me know. I was also thinking of that same area on pass toe board. I'm still undecided if I will have a straight run to the starter or a bulkhead connector.
 
#19 ·
I have less issue with the bulkhead on the hot than i do on the ground. I am not a believer in carrying the starter ground from the trunk through the chassis on a more or less stock bodied street car. If the bulkhead rattles loose on the hot you may get a warmed up connector or a fail. What you dont get is your current finding path B. I was reading an old post over on lateral g where a guy was wrestling with this and it got me thinking about the bulkhead on the neutral. Regardless i will be running a 1/0 ground between the engine and the chassis along with a cable back to the trunk.
 
#20 ·
Very good. My ground in the trunk from battery will only be approximately 12 inches long to vehicle chassis. I will also have additional grounds from engine to body.
 
#22 ·
I have used these type of grommets before and been very happy with them:

Ancor Marine Grade Electrical Wire Seal - Round Cable, 4 to 1/0 AWG, 1

I would prefer doing a pass through with a cable instead of a bulkhead stud type as you have less connections and less possible unprotected spots. The above also has a nut that tightens down and compresses a seal around the outside of the cable. When I have installed these, I drill the hole in the metal, paint the edges of the metal, run a bead of caulk around the edges then install the grommet. I then pass the cable through the grommet and terminate the end of the cable, then tighten the sealing nut so no water can get from one side to the other.

As far as people running no protection on a wire and thinking a ford type solenoid or master on/off switch is enough, to me it is not and any wire or cable needs to be protected with a fuse, fusible link, or circuit breaker. While it may never happen, the contact points in a relay can weld themselves together if the situation is right and removing the switched signal from the relay does not cut power out of the relay. In your house you certainly do not run any unprotected circuits off of your breaker panel, so why do it in a car.

Jim
 
#27 ·
I hope what I offered helps.

Any protection device such as a fuse, circuit breaker, or fusible link needs to be at or as close as it can be at the source of power. Anything between it and the source of power will be unprotected by this device, while anything after it will be protected BUT we have to keep in mind the layout of things and what is connected to it as well as wire sizes and wire lengths.

Just because you can put a 30A fuse on a wire does not mean things are protected. It depends on what the fuse is needing to do as well as what kind of wire is attached to it.

Let's say we have a short length of wire, let's say 12" long off of a battery going to the input of a fuse and then after the fuse, or the output side, we have a 10' wire attached to it that then runs forward and connects to something like a cooling fan switch and then after the switch another length of wire connects to the cooling fan motor.
On this, if we had a short to ground anywhere PAST the output of the fuse, the fuse should blow.
If there was not a fuse off of the battery and ANY wire, cooling switch for the fan or in this case the cooling fan motor itself were to short to ground then at that point of the short ALL the way back to the battery, this wire and/or parts would become red hot, then start melting the insulation off of the wire, then possible melt into yet another wire it is laying against causing it too to then become shorted to ground and it can go on and on until the battery goes dead or the wiring then ignites something in or around the car and then you have a fire.

Another way I have seen things wired, is there is a feed wire off of the battery to something like a master on/off switch and then a fuse is installed after that and knowing that anything before the fuse is unprotected, if the terminals of the master on/off switch were to short to ground, the fuse would never blow as it is AFTER the switch. Some could say, well the studs on the back of a master on/off switch are covered and a short there cannot occur but then look at the switch itself. While it's a remote chance, what if the internal parts inside the switch were to short to ground. With a fuse AFTER the switch and no protection BEFORE the switch, the connections between the switch and the battery will become very hot, melt insulation off of the wire, and possible do even more damage.

While I would like to say that every master on/off switch, any starter solenoid, or any other switch or device will never fail, it could and if we think might what happen in a serious accident, wires can become pinched and shorted.

When you ask the question of "would the 300A fuse be after the battery and before the F solenoid" I have to answer it that the fuse, and it might not be a 300A size, yes would go between the battery positive post and the F solenoid. Anything between the input side of the fuse and the battery positive post is NOT protected. This get's back to the questions I asked a poster on the Chevelle site. He might be running a high torque starter and not need the power like a standard GM starter would require, nor do I know if he is attempting to turn over a high compression motor with a gear drive starter or a regular starter, and do not know what cable size and type he has from the trunk to the starter. Getting back to how a doctor cannot prescribe things properly without enough information, the same holds true here. A 300A fuse might work, and it may not.

Here is yet another style of fuse I've seen and this has the fuse as close as I've ever seen to the source of power which in this case is the positive battery post:







A thing I want to do is see how these cube fuses compare against an ANL and an ANN style fuse as far as operating characteristics. Below is the specs on the one companies cube fuse while below that is a spec sheet on an ANL/ANN style. I have to think that some react like a fast blow fuse, while another has more of a time delay before they blow. It's just how they are designed.









I recently came across this picture of a battery cable that was not protected on an 18 wheeler and it melted the battery also:







Kinda wonder what the repair bill was on that to where if it had a properly located and sized fuse, they would only be out for a new cable, a new fuse, and the labor to replace those things. It looks like they had a considerably higher bill and luckily just damaged what they did.

Another thing to notice is the ANL style fuses are designed for lifttruck and other battery operated systems

Jim
 
#29 ·
Donny, that bulkhead connector I posted back a little won't work cleanly so it's a dead idea. I might wind up running direct like Jim did. I think it's a better way to do it electrically, it's just not my favorite way to go through assembly.
Jim, There are 2 sweet spots to locate that seal strain relief, one favors the subframe mount, the other the trains tunnel. Which did you choose? Could you allow the cable some flex room or did you have to bend it over?
We use those cable seals all over the place at work both plastic and stainless. They are effective.
 
#31 ·
Jim, There are 2 sweet spots to locate that seal strain relief, one favors the subframe mount, the other the trains tunnel. Which did you choose? Could you allow the cable some flex room or did you have to bend it over?
We use those cable seals all over the place at work both plastic and stainless. They are effective.
My car is a 73 Nova, which has a lot of same things in the firewall and subframe, and the interior is highly modified and where I came through, I actually have two holes on the firewall face. One for the 1/0 for the starter and the other for a 1/0 alternator wire. While I did this car many,many years ago, below is the area I believe the holes are at. I do remember I took the ring terminal on the 1/0 wire for the starter and bent it on a 90 degree angle so that the cable went directly rearward to the firewall face. With a lot of things changed on my car with the 1/0 wire off of the alternator run to the rear, I have it on some Adel clamps bolted to where the original spark plug shields attached to and also have the 1/0 wire inside of some old braided steel line heater hose. I did this to help protect the cable from heat as well as abrasion.

Here is about where I made the holes off of memory but they may have been a bit lower:



Like I said, I did mine back in the early 90's and the more I think about it I may have also gotten some of the threaded type of compression grommets from an electrical supply place with a longer tube on them and might have taken a section of tubing and cut it in half on a diagonal so I could have it going through an angled surface but still be level.

On mine, the cables go straight back hugging the starter solenoid and the motor on mine I believe lifts up on the driver's side when accelerating and with the cables on the passenger side of the motor I don't think there is much movement. Mine being a 73 also has the clamshell motor mounts which may offer less movement that the older type of motor mounts.

I know on mine I had the motor in place and mocked things up where to run things so don't do it blind thinking you may have enough clearance as you might not. On mine too, I ran 1/0 Esoteric brand copper wire and it is a very finely stranded wire which means it can bend more easily than a thicker stranded type of cable.

Jim
 
#30 ·

Attachments

#32 ·
Here is my cable kit:
On the cable kit, is it CCA (copper clad aluminum) wire ?. If it is, be aware that a 1/0 CCA wire is below 1/0 copper wire as for as ampacity. I don't know what your current/amperage demands are but a 1/0 CCA cable from what I've read is about equal to a smaller 2 gauge copper cable. When people are designing for the wire gauge that needs to be used, most charts are designed or made for copper wire specifications and a person needs to go to a larger gauge CCA than if copper cabling was to be used. Also, if it is CCA, go over the tightness of the connections after a while as aluminum is softer and expands and contracts more than copper and what was once a tight connection can become loose.

Jim
 
#33 ·
Jim, i see you went through the cowl on the vertical face. Your cowl/floorboard is a little different there then mine. This weekend I will get my heater boxes in and see if i have enough room to fit a seal in between the edge of the box and the formed radius in the floorboard. Some of the other posts i was reading have the perforation in the short horizontal return ledge adjacent to your notation which is where i assumed, duh, you were located too. That ledge section is different.
 
#34 ·
I am kitting this together. I have 1/0 royal excelene welding cable in red and black. I am curious if the lugs you will use will fit through the base of your seal. I didnt get lugs yet and if i get a seal that will pass a lug through the base i will use them in the battery box too.
 
#40 ·
Resurrecting this thread as its the latest I can find that addresses the pass through of the battery cable into the engine compartment. I am ready to put both my battery cable (1/0) and my alternator cable (10 ga I think) through my firewall and can't really decide how to do it. Grommet, bulkhead connector or something else. Currently my cable is running in the trough up the passenger side under the wire guard. I am thinking I will continue forward on the rocker shelf between carpet/guard and kick panel and then exit somewhere in line with this area partially up the firewall.

I see in this thread a lot of conversation about the electrical fitting being used but I can't envision how you would drill a 1" hole anywhere in the toe kick/firewall area and not have a large semi-loop of cable where you thread it through? The bulkhead connector makes sense because the stud is at a right angle to the surface the cable is following but again, more connections, more potential issues.

I know many of you have done this mod so any feedback and especially pictures would be helpful.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top