Trunk mounted battery

-

SRT_DSTRHOLC

Well-Known Member
Joined
Mar 20, 2008
Messages
6,468
Reaction score
203
Location
USA
So I plan I using this diagram that was created by Crackedback. I wanted to know what is recommended for wire gauge for each and every wire.

So below is a list:

Wire from Alt to continous duty solenoid:
Wire from CD solenoid to Master disconnect switch:
Wire from CD solenoid to Ford solenoid:
Wire from Battery ground to car: I assume 0-1 gauge
Wire from CD solenoid to + on Battery:
Wire from + on battery to Ford Solenoid:
Juper wire from post to post on Starter:
Wire from starter big post to Ford Solenoid:
Wire from Ford solenoid to Mopar relay:
Wire from Master disconnect to Mopar relay:

I believe that should be it. Any help would be great!
 

Attachments

  • trunkbattwireRY.jpg
    60.7 KB · Views: 6,975
The above diagram will work but will not pass NHRA tech rules. Because both ford solenoids are not cut by the disconnect switch, if either solenoid fails closed, you could have a fire.
 
Wire from Alt to continous duty solenoid:......................................4 gauge
Wire from CD solenoid to Master disconnect switch:.......................10 gauge
Wire from CD solenoid to Ford solenoid:.........................................1 gauge
Wire from Battery ground to car: I assume 0-1 gauge.....................correct
Wire from CD solenoid to + on Battery:.........................................1 gauge
Wire from + on battery to Ford Solenoid:.......................................1 gauge
Juper wire from post to post on Starter:.............I use a solid piece of copper
Wire from starter big post to Ford Solenoid: ..................................1 gauge
Wire from Ford solenoid to Mopar relay:.......................................10 gauge
Wire from Master disconnect to Mopar relay:.................................1 gauge
 
The above diagram will work but will not pass NHRA tech rules. Because both ford solenoids are not cut by the disconnect switch, if either solenoid fails closed, you could have a fire.

Really? Been wiring cars for close to 25 years using this style set up. Never failed a NHRA tech inspection yet.

The alt line solenoid IS NOT a ford starter solenoid. It's a continuous duty relay. If the CD relay happened to lock closed, you are in no worse position than the folks that wire straight from the alt to battery positive post. The direct alt line passes tech every week and has for 40+ years.

One change to make if you are driving a street car. The line that energizes the Alt line CD relay should come from a switched/keyed source. The way it's wired in the above schematic will have a constant draw when the master power switch is in the on position. May run the battery down if you forget to switch off the master when parked for any duration of time.

Poison, HaHa, you could also use a Jeep solenoid... LOL :)
 
Really? Been wiring cars for close to 25 years using this style set up. Never failed a NHRA tech inspection yet.

The alt line solenoid IS NOT a ford starter solenoid. It's a continuous duty relay. If the CD relay happened to lock closed, you are in no worse position than the folks that wire straight from the alt to battery positive post. The direct alt line passes tech every week and has for 40+ years.

One change to make if you are driving a street car. The line that energizes the Alt line CD relay should come from a switched/keyed source. The way it's wired in the above schematic will have a constant draw when the master power switch is in the on position. May run the battery down if you forget to switch off the master when parked for any duration of time.

Poison, HaHa, you could also use a Jeep solenoid... LOL :)


Lol I said ford because that's what is written haha but I purchased a jeep one :)... Thank you Cracked. How would you suggest wiring that Alt line so that it's switched? I believe both of these relays will be mounted in the trunk next to the battery.
 
How big is the alternator?

Wire from Alt to continous duty solenoid: 4 or 6 gauge
Wire from CD solenoid to Master disconnect switch: 14-16 Little to no load trigger with key
Wire from CD solenoid to Batt pos or Ford solenoid battery side: 4-6 gauge
Wire from Battery ground to car: I assume 0-1 gauge
Wire from CD solenoid to + on Battery: 4-6 same as wire from cd to ford relay above
Wire from + on battery to Ford Solenoid: 1/0 or bigger
Jumper wire from post to post on Starter: 14
Wire from starter big post to Ford Solenoid: 1/0 or bigger
Wire from Ford solenoid to Mopar relay: 14-16
Wire from Master disconnect to Mopar relay: 8-10

If you pull headlights and electric fans straight off the alt post, that will reduce the load on the wire from the master disconnect to mopar relay.

Visualize the two relays/solenoids stacked on top of each other in the schematic. The alt line runs in one side of the CD relay and you make a short jumper to the battery + side of the ford/jeep starter relay. Makes things a bit cleaner.

Here's a pretty good wire sizing chart.
WiresizingchartBW.jpg
 
How big is the alternator?

Wire from Alt to continous duty solenoid: 4 or 6 gauge
Wire from CD solenoid to Master disconnect switch: 14-16 Little to no load trigger with key
Wire from CD solenoid to Batt pos or Ford solenoid battery side: 4-6 gauge
Wire from Battery ground to car: I assume 0-1 gauge
Wire from CD solenoid to + on Battery: 4-6 same as wire from cd to ford relay above
Wire from + on battery to Ford Solenoid: 1/0 or bigger
Jumper wire from post to post on Starter: 14
Wire from starter big post to Ford Solenoid: 1/0 or bigger
Wire from Ford solenoid to Mopar relay: 14-16
Wire from Master disconnect to Mopar relay: 8-10

If you pull headlights and electric fans straight off the alt post, that will reduce the load on the wire from the master disconnect to mopar relay.

Visualize the two relays/solenoids stacked on top of each other in the schematic. The alt line runs in one side of the CD relay and you make a short jumper to the battery + side of the ford/jeep starter relay. Makes things a bit cleaner.

Here's a pretty good wire sizing chart.
WiresizingchartBW.jpg

It is a 1 wire mini 60 amp. I have all new wiring from American autowire
 
2014 NHRA rule book section 20, page 35, 8:4 Master cutoff

Same as it's been for a LONG time and never failed an inspection. Thousands of cars that pass NHRA tech every weekend use a ford solenoid in the trunk wired just like that schematic.

If you want the starter draw going through the master, then have at it. Some of us don't like a big honking wire when the master is on going forward.

Reality is, if the master kills the engine and fuel pump, they pass you.

Until a tech inspector or NHRA says it's not OK to wire that way, it's staying. My starter may run away if the ford solenoid gets stuck closed. When it happens it will be a first for myself and anyone that I know. My way may not make you happy or your interpretation of the rule, and that's OK.
 
Lol I said ford because that's what is written haha but I purchased a jeep one :)... Thank you Cracked. How would you suggest wiring that Alt line so that it's switched? I believe both of these relays will be mounted in the trunk next to the battery.

Find a wire coming out of the fuse block that is hot when your key is on and use that to switch the CD relay.
 
Find a wire coming out of the fuse block that is hot when your key is on and use that to switch the CD relay.

okay and this is where I get sligtly confused...Do I wire it directly like the diagram is and then just add an additional wire that is switched to the post that the alt wire is connected to or what?
 


Here I made this one up just now. Stacked relays, wiring...
 
How reliable is that CD relay? Is this a setup that could be used in a car that might get driven for 3-4 hours at a time with only maybe a 15-45 minute break between legs, say from Spokane to Vegas?
 
How reliable is that CD relay? Is this a setup that could be used in a car that might get driven for 3-4 hours at a time with only maybe a 15-45 minute break between legs, say from Spokane to Vegas?

I haven't had any issue with them. I always carry a jumper wire to go around the CD relay in case of failure.
 
Here's another way to do a trunk mounted battery with a cutoff switch. Not saying this way is better by any means, it's just a different way to accomplish it. This is how I wired my Duster, no issues with it so far. Haven't had it to the dragstrip to pass tech yet, but the cutoff kills everything outside of the trunk so I don't think it should be a problem.

In order to do it this way you need to have a 4 pole cutoff switch and a high amperage continuous duty relay, I used Moroso parts for both. The diagram illustrates a stock Mopar alternator output, although it should be even less complicated for a 1 wire setup.

batt-cuttoff_zps468a9a9f.jpg
 
That's too hard. The easy way is to run the alternator wire through a toggle switch. A pretty stout toggle switch. One that'll handle the current. Then run another alternator wire through your battery switch. When at the track flip the toggle switch off or just disconnect the original alternator wire and your new alternator wiring will run through the battery switch. It'll kill the engine when the switch is turned off.
 
All of that tom-foolery just to avoid a second wire to the alternator?
 
I personally don't think these "Ford solenoid" setups are worth doing. You still have to run large gauge wires for the alternator and main power and both of these wires are just as capable of starting a fire as the main battery cable. I just make sure the main wire is routed securely, use grommets and protect from chafing, and inspect it regularly. As for any worst case scenarios caused by a hot wire running through the car, you've already mounted the battery near the fuel tank, what can possibly go wrong?
 
I personally don't think these "Ford solenoid" setups are worth doing. You still have to run large gauge wires for the alternator and main power and both of these wires are just as capable of starting a fire as the main battery cable. I just make sure the main wire is routed securely, use grommets and protect from chafing, and inspect it regularly. As for any worst case scenarios caused by a hot wire running through the car, you've already mounted the battery near the fuel tank, what can possibly go wrong?

When you have a car burn to the ground because of always hot wires, you'd likely change your mindset. Even fused lines won't save what happened to us. The fuel cell is low on the potential danger list.

When I throw the cut off, nothing outside a 2' cube is hot in my car.

There are minimum levels of safety and there are improved levels. Pick your approach. Like I say... pick your parts, pay your money.
 
When you have a car burn to the ground.


You guys might want to listen

The "crash guys" should be able to run up to the car, KNOW that they can "kick at" the disconnect and KILL ALL POWER and that the disconnect will kill the engine as well as get rid of all power in the car

That toggle switch is not gonna do you any good if you are laying there half goofy in the driver seat and likewise that no6, no 4 charging line from battery to alternator makes a fine welding wire if it does not go through the disconnect

You can thank "all that tom foolery" when you are laying there upside down with fuel running down your nose, eh?
 
When you have a car burn to the ground because of always hot wires, you'd likely change your mindset. Even fused lines won't save what happened to us. The fuel cell is low on the potential danger list.

When I throw the cut off, nothing outside a 2' cube is hot in my car.

There are minimum levels of safety and there are improved levels. Pick your approach. Like I say... pick your parts, pay your money.

I said hot wire, I didn't say hot all the time. If the car's running, the wires are hot, if the switch is off nothing is.
 
I said hot wire, I didn't say hot all the time. If the car's running, the wires are hot, if the switch is off nothing is.

Please provide a wiring diagram that doesn't have a hot alt line with the switch off.

Please don't provide one that has the failure prone switches.
 
-
Back
Top