Do you really home run wires to the battery?

[Gizmosrcool]

Hi Everyone.

I am beginning to think about how best to route wires. A number of products indicate to connect directly to the battery. This includes EFI ECUs, starter, Alternator, CD Box, etc. Seems like a lot to go direct to the battery. Is it really needed?

I have the FF on-off switch. I am thinking of running a 2ga wire from the battery to the switch. It has a A and B side. I’ll run to the A side and then run a pigtail to the B side. This now switches the A and B and I can use to turn everything off with a single master switch.

I can use the A side to go to the starter and maybe alternator. Or just the starter and I’ll run the alternator to the battery. That would be just two connections to the battery.

The B side can be used for ECU, CD Box, and run to the harness and other items needing power. If I need too. I can always make an always on circuit for anything.

What do you think of the plan? I appreciate feedback and what folks have done.

Thx. Tom

[kirby]

I put a power distribution block in for my wiring. I am then running a single cable to the battery in the trunk. Other more experienced folks will chime in I a sure.

188262

[Rdone585]

Check your alternator. Mine will run down the battery if it's directly connected and the engine isn't running.
I have my battery going to a cutoff switch that disconnects all power, even the alternator from the rest of the car. This is so the car will completely stop if the switch is turned off. From the switch I run to a distribution panel where many things are "directly connected to the battery", but only when the switch is on. The way I understand power distribution is that tall these (especially digital) devices want raw power with as little noise as possible. Each of the items you mentioned will produce noise that can make it's way onto the power line if not distributed properly. Even having a power wire running near a noise source can cause issues for some devices.

[AC Bill]

A common method was to run wires from the remote solenoid post, because the battery was wired directly to that. It made for shorter runs if you had the battery in the trunk, and the master switch between the seats. You could just use a heavy duty connection block if you didn't have a remote solenoid. I wouldn't run all the items mentioned directly to a battery post.

[Gizmosrcool]

Yes I plan on a distribution block. I am good with wiring. It seems every manufacturer wants a direct connection. I am guessing they get a lot of tech calls and folks run power very creatively.

Thx for the replies. Tom

[edwardb]

I've seen the same thing. Many aftermarket products want a direct connection to the battery. It's a conservative approach that eliminates circuitry variations. For my builds, I've only ever had one connection at the battery. Then a larger size cable (typically either 2 or 4 gauge depending on the build) to either a master cutoff on the firewall or a large binding post. Then I do all the connections from there, e.g. starter, alternator, RF harness power, EFI, etc. For my Coyote builds, I used a master disconnect and put the Coyote PDB wire on the unswitched side so they're powered all the time. That's per the Ford instructions. I suspect other EFI setups are similar. Everything else I have on the switched side. For my recently finished truck build, no master disconnect. Just a firewall mounted binding post and everything attached there.

[i.e.427]

As much as it pains me to disagree with Paul, I'm going to. If it were just a Ford Control Pack I would say yes, Paul is right. However, reading the end of your original post I see ECU and CD Box, which suggests you are running an aftermarket F.I. setup. Whether it is FiTech, Holley or another, they all state main ECU power must be run DIRECTLY to the battery. The reason (as they state in their literature) is that the battery acts as a buffer (or conditioner) for the ECU to absorb any stray RF interference. I can't tell you how many folks miss this part and end up in all kinds of trouble with their EFI system having issues. If the instructions, for your system, tell you to run DIRECTLY to the battery, then do.

Frank

[maclonchas]

Tom,

Think that Frank and Paul all have good points and valid reasons for connecting directly to the battery or a power distribution block. I would recommend you move the battery to the engine compartment and reduce the length of wires for the whole run. You have many options depending on your engine setup, cranking needs and peripherals in the engine bay. They options range from a smaller battery on top of the passenger footbox, Breeze forward battery kit or buying a battery box and affixing it yourself to the X-bar. The reduced runs will allow you to truly minimize homers lengths and determine what devices need to be hooked to the battery that minimize RFI or limit the sources that can drain the battery directly.

Hope this helps.

Bill

[edwardb]

As much as it pains me to disagree with Paul, I'm going to. If it were just a Ford Control Pack I would say yes, Paul is right. However, reading the end of your original post I see ECU and CD Box, which suggests you are running an aftermarket F.I. setup. Whether it is FiTech, Holley or another, they all state main ECU power must be run DIRECTLY to the battery. The reason (as they state in their literature) is that the battery acts as a buffer (or conditioner) for the ECU to absorb any stray RF interference. I can't tell you how many folks miss this part and end up in all kinds of trouble with their EFI system having issues. If the instructions, for your system, tell you to run DIRECTLY to the battery, then do.

Frank

No worries Frank. I post what has worked for me and what I described has been used on multiple builds. In each case (other than the truck) the builds had front mounted batteries and a relatively short run of larger gauge cable to the firewall. Hard for me to believe there's any difference from going directly to the battery. As I'm sure you know, Ford Performance also says to home run the power (and ground) wires to the battery. The two Coyote builds I've done I wired as previously described. Both have been solid over the long term. The truck build has an LS3 control pack. But the battery is back under the bed. For that I used a large feedthrough at the firewall for the LS3 power plus everything else.

But you obviously have much more experience than me and more diverse products. I absolutely defer to that for the reasons you cite. I guess mainly the point here is you can be selective on what you home run to the battery. No need to have everything as the first post describes.

[Blitzboy54]

I only have my Sniper connected directly to the battery. The other main positive leg goes to the starter and then piggy backs from there. I have not had any issues.

[rich grsc]

Frank is spot on with his reason an explanation of why.

[Gizmosrcool]

Thank you everyone. The information helps. I am going to tweak my plans and not use a master switch. It’s defeated with the direct connections. I do not see situations where it will be needed for participation. It’s a fun car. Not a serious racer.

That said. I am using the breeze front mounted battery box. I’ll run a 2ga to a terminal block and pickup the starter, alternator, and peripherals. I’ll run along the frame rail and jump up to the firewall.

All the fancier electronic equipment will run a different path, using the side rails, and I can go from the dash area, on the PS side, down to the battery. I am planning sniper terminator stealth to separate the ECU from the TBI. I may look at the new v2 of regular sniper as it touts better and hardened RFI. Either way, the separation per ie427 Frank should minimize stray RF interference.

Thx again for the feedback and information.

Tom

[Hoooper]

What ECU are you using? Some aren't designed or wired as well as others and suffer from a lot of interference issues. Others aren't so much of a problem. I'm running a haltech, all of the wires that would cause interference or suffer from interference are shielded. The manufacturer still says like all other to wire the ecu power supply to the battery but they also say if you are using a disconnect to wire through the disconnect. I ran mine through the disconnect and have no problems. If I were running something like a sniper that has common issues with interference I might have a different approach

[edwardb]

Thank you everyone. The information helps. I am going to tweak my plans and not use a master switch. It’s defeated with the direct connections...

By all means, don't use one if you don't want to. But FWIW, and perhaps clarification of what I said, the only wire on the hot side (unswitched) of the master disconnect in my case is the Coyote power lead. Other than the main battery lead of course. So that it's always on per instructions. The power draw for this keep alive function is miniscule. All the other leads that I described are on the switched side and the car won't run or start with it switched off. I like it for maintenance purposes and also for winter storage. But certainly not mandatory.

[Gizmosrcool]

I am using a Holley terminator X stealth system with Ecu control of the timing. This includes the hyperspark CD box and distributor. CPU separate from the 4150 TB. I am going with an Infinitybox ECU for my power and wire management. All of this likes a direct connection.

I looked at edwardb’s last mk4 build and liked the way did it for his Coyote. That is what I started with. But as I reviewed the instructions for everything, so much wants a direct connection for different reasons. Now a switch does make much sense anymore.

My new thought is to create two power distribution points off the battery. Point 1 will be for the battery, starter and alternator. Everything says do not connect to the alternator or the starter. That makes sense given Franks comments on RF. Point 2 will power the ECUs and I’ll run those cables a different path and provide separation for critical stuff like cd box and distributor trigger wires.

I am sure it’s a plan in progress. It’s already changed a few times. Next step is get the battery box in and electrical wires and ends ordered.

Thx again for all the feedback.

Tom

[Papa]

My Holley Terminator X and MSD CDI box both want home runs to the battery. I used battery terminals with multiple connection ports to accommodate the necessary connections. I also followed the general approach (less the main cutoff) that Paul described for powering the bulk of the primary circuits. I ran a 4-gauge wire from the battery to the starter, and another from the starter to a buss bar. I connected all the RF power leads to the buss bar as well as the main power for a couple of relays I used in my setup.

https://thefactoryfiveforum.com/attachment.php?attachmentid=84659&d=1524442084

https://thefactoryfiveforum.com/attachment.php?attachmentid=84660&d=1524442093

The fourth post on the buss bar is where I connected the 4 gauge wire from the starter post.

The battery terminals I used are here:

https://thefactoryfiveforum.com/attachment.php?attachmentid=167457&d=1653935246

https://thefactoryfiveforum.com/attachment.php?attachmentid=167458&d=1653935246

https://thefactoryfiveforum.com/attachment.php?attachmentid=167459&d=1653935256

[Gizmosrcool]

Papa. Thx for the info. Do you recall the name of those terminals?

[Papa]

Papa. Thx for the info. Do you recall the name of those terminals?

These are what I used:

https://www.amazon.com/gp/product/B07DFJP27D/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

It looks like they are no longer available, but there are many other options that are.

You'll also want to get the appropriate crimp connector ferrules for the specific wire gauges you are using. Here is an example for the 4awg connectors:

https://www.amazon.com/Connector-Terminal-Insulated-Ferrule-E25-16/dp/B07FLHW29H/ref=sr_1_5?crid=13LH5Z0YKXRSN&keywords=crimp+connector+ferrule+4awg&qid=1691368645&sprefix=crimp+connector+ferrule+4awg%2Caps%2C163&sr=8-5

[Gizmosrcool]

Thx Papa. I'll take a look.

[BrewCityCobra]

Hi Everyone.

I am beginning to think about how best to route wires. A number of products indicate to connect directly to the battery. This includes EFI ECUs, starter, Alternator, CD Box, etc. Seems like a lot to go direct to the battery. Is it really needed?

I have the FF on-off switch. I am thinking of running a 2ga wire from the battery to the switch. It has a A and B side. I’ll run to the A side and then run a pigtail to the B side. This now switches the A and B and I can use to turn everything off with a single master switch.

I can use the A side to go to the starter and maybe alternator. Or just the starter and I’ll run the alternator to the battery. That would be just two connections to the battery.

The B side can be used for ECU, CD Box, and run to the harness and other items needing power. If I need too. I can always make an always on circuit for anything.

What do you think of the plan? I appreciate feedback and what folks have done.

Thx. Tom

A little late to the party here but I fabricated a battery circuit that I think mirrors what you were looking to do here.

https://thefactoryfiveforum.com/showthread.php?38979-The-Brew-City-Cobra-427W-IRS-Side-Pipe-Fitment&p=482433&viewfull=1#post482433

I also used the main cutoff switch to isolate the battery, alternator, and starter motor. The "main bus bar feed" shown in the schematic is the Blue Seas Systems bus bar that ultimately feeds the rest of the car (e.g., the main fuse block, secondary fuse blocks, and the like).

By doing it this way the bus bar can be placed behind the dash and a bit less exposed (if that is something you would prefer).

188428

Hope this helps.

[Tremelune]

Electrically, there isn't much reason to run multiple cables to the battery vs running one large gauge cable and distributing it up front. The battery will remain part of the circuit, and power will come from the alternator or the battery—almost always the alternator while the car is running, since the battery is just another load (like a headlamp) when the car is running. The battery can still act as a buffer during large spikes the alternator doesn't handle.

It's worth noting that a fuse should be used everywhere the gauge of wire decreases. If you run a 2awg wire and split it off into an 8awg, 10awg, 12awg etc...You want fuses for each. I like little fuse boxes over power distribution blocks for this reason.

The finicky bit with regard to EFI and ECUs is small voltage disparities between the computer and various sensors. That has a lot more to do with how they're grounded than where the hot leads come from...You want to ground them all to the same place (like the engine, but not necessarily the same engine bolt):

https://www.haltech.com/news-events/ecu-grounding-the-dos-and-donts/

[Alan_C]

Electrically, there isn't much reason to run multiple cables to the battery vs running one large gauge cable and distributing it up front.

Actually there is a difference IMO. I am building a 70 Mustang restomod with the battery in the trunk. I have a dual run from the battery. I have a 1 gauge cable, fused, from the battery direct to the starter. I have a second parallel 6 gauge run, fused, from the battery to the power distribution box mounted in the upper passenger footwell. The body wiring harness then connects to the PDB. Why did I do this, because of the current load the starter places on the 1 gauge cable during cranking and the resultant voltage drop at the end of that cable. I had a forum member put a clamp style amp meter at the starter on his 1st Gen Coyote. The peak current draw measured was 175A. The PCM is sensitive to voltage drop as are most EFI computers. With the approach I have taken, the PCM will see the voltage drop at the battery and not the drop at the end of the 1 gauge starter cable. If I remember correctly, Ford Performance warns against having the PCM more than 10 feet away from the battery. The parallel run approach I have taken will minimize the voltage drop seen by the PCM during cranking. Although possibly excessive, I am confident that I have a configuration that should minimize the voltage drop seen by the PCM.

[Tremelune]

That's a valid approach, but pulling 175A through the 1awg wire is the weak link. For a long cable to the starter, you'd still be better served using 2/0 and running the smaller gauge to the ECU off of that...

That said, it would would make fusing more expensive, and if the 1 and 6 gauge wires starts the car, it starts the car, and smaller wire is easier to come by...

I can see your point.

[rich grsc]

That's a valid approach, but pulling 175A through the 1awg wire is the weak link. For a long cable to the starter, you'd still be better served using 2/0 and running the smaller gauge to the ECU off of that...

That said, it would would make fusing more expensive, and if the 1 and 6 gauge wires starts the car, it starts the car, and smaller wire is easier to come by...

I can see your point.
No one needs a 2/0 cables to start these cars. My other car had the battery in the trunk, I used the cable that was supplied with the kit. Once I put on a mini-starter it started every time, never an issue

[Rdone585]

My other car had the battery in the truck Sorry rich but I couldn't help but get a laugh visualizing your truck following the car with a battery cable attached. But you make a good point - 2/0 gage wire is a huge overkill. Waisted money, weight, and headache running the super stiff wire.