Battery to trunk-would this work?

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standup303

standup303

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I want to put the battery in the trunk and want a disconnect in cab for security purposes. I am not worried about NHRA guideline but…. if I went this route could I just add a master disconnect to the line side of the Ford relay to be within NHRA guidelines down the road?

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No. There has to be a way for the engine to run. In other words, how does the alternator feed the electrical system?
 
Mattax said:
No. There has to be a way for the engine to run. In other words, how does the alternator feed the electrical system?
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Ah gotcha, so I could do another wire from the line side of the Ford solenoid to the engine bay starter relay?
 
standup303 said:
Ah gotcha, so I could do another wire from the line side of the Ford solenoid to the engine bay starter relay?
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Yes. Then it would run.
If you connected the alternator directly to the battery, and put the kill between the battery and the junction to feed the system, the kill would work - no power to ignition - engine doesn't turn - self feeding alternator doesn't turn.
I don't know if it would meet NHRA. I know someone who made a similar arrangement (but standard alternator regulation) that was apparently OK with the vintage road racing association he was running in. I dont recall the details and I dont think I want to.

The disadvantage of a one wire so far away from the main splice is the resistance. The alternator thinks its producing at say 14.3 Volts (which it is) but at the (headlights, ignition, etc) voltage may be lower. It will be worse with lots of things running and the battery recharging. It may be barely measureable if at all with the battery recharged and driving with no extras running. Size the wires for the maximum electric load and distance and should be alright.
 
What I did was install a Normally-Open relay into the Isolated Field wire charge circuit. As soon as I pull the handle, the relay de-powers and opens the field circuit, and the alternator powers down. That circuit does not draw much so I just used a small relay. I also run my Ignition off a relay.
I installed those about 20 years ago. I think this does NOT meet NHRA rules but IDK for sure. I just use my car on the street, and no electric pump.
 
You don't need the big ole ugly Ferd relay. You can buy a 150 amp relay with spade lugs, not much bigger than the common Bosch 30 amp relay.
 
Found this wiring diagram by a member here. What is the “Switched power source”that controls the alternators continuous duty relay?

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I could be wrong, but that sounds like the 12v from the ignition on, taken from just before the ballast resistor
 
Couldn't you intercept the ground cable? You could run a 4 gauge cable...It seems that a system without grounding to the battery cannot start.
 
The master disconnect switch on the negative side is not NHRA legal . I did something similar to the wiring diagram on my race car, the starter relay is near the battery in the rear, and the battery cable is only hot when the starter is cranking
 
standup303 said:
Found this wiring diagram by a member here. What is the “Switched power source”that controls the alternators continuous duty relay?

View attachment 1716193988
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Trunk Mount Battery - Wire Routing

For those with trunk mounted batteries, how do you prefer to route the starter cable and alternator charge wire? I'm doing some electrical planning for my 66 BB Dart build and am trying to figure out the best way to rout these large cables (e.g., along the frame rails, through the interior, etc.)
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questions about battery disconnect wiring

i relocated the battery to a trunk used a sealed box kit. a 4 post disconnect switch. i have the 10g wire ran to the back but im confused on what to do with the alternator wiring. i have it wired to the 4 post on the small positive lead on the switch then to the positive terminal on the battery...
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Post #13. Sorry, tried to upload a pic. The 150 amp relay looks like a slightly larger version of the Bosch 30 amp relay. I can buy here from electronic stores.
 
Sterling said:
The master disconnect switch on the negative side is not NHRA legal . I did something similar to the wiring diagram on my race car, the starter relay is near the battery in the rear, and the battery cable is only hot when the starter is cranking
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Correct. And the reason for that is, a car's electrical system will ground ANYWHERE IT CAN if you're not very careful. The power side is much easier to isolate.

While he may not be looking for the NHRA legal way, nine times out of ten, that's the safest.

What I would do if I ever do a trunk battery conversion and I may, is use @crackedback's trunk wiring setup to the TEE. That's why I have it saved. That's the diagram referred to in post #8.
 
It doesn't matter whether you isolate the neg or the pos side of the battery, they are 'equal'.
If you isolate the negative ground connection of the battery, & accidentally short to grd the large terminal on the starter....nothing happens.
 
Going to roll with the diagram in post #8 except for the master switch being located in the rear most part of the car I will install a switch somewhere in cab for more of a security feature. Running 1/0 welding cable for the pos/neg to relays and to the starter. #4 welding cable to alternator. #10 THHN for all control wiring. Thanks for the help all.
 
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