Sniper and Trunk Battery help
I think I am finally catching up with you. I am using a 4 pole Master disconnect with an amperage rating that meets the alternator output.
I finally spoke with Painless performance and the shutdown relay is designed to be wired into the charge wire and be placed on its own 2 poles on the disconnect. It has load protection built in. It is also designed to work to prevent any surge when flipping the disconnect. I can run the charge wire to the battery side off the relay and through the hot post of the solenoid. The ground goes to the other side of the switch. When the disconnect is open the relay kills all power post relay. I also wired in a 150 am fuse into the charge wire pre-relay.
When the disconnect is open the hot wire coming from the disconnect to the starter solenoid has nowhere to send charge as it is now open and the relay circuit it incomplete.
In theory, there should be no wires left hot when the disconnect is opened on both poles as the power should be shut down to the entire system.
The ford solenoid which is a continuous duty relay is also rated as a starter solenoid. Its the same one I use on my diesel dump truck. It starts a DT466 so I would assume it could start a 440 gasser for intermittent use. But maybe I am wrong?
I really appreciate the tip about the EFI wiring/NHRA regs needing to go to the switched side! I will have to redo that part even thought the holley manual states directly to the battery.
I just don't get why ground kill wouldn't be better but I have had a hard enough time working through this. Ugh
Ground kill would OF COURSE be the correct way to go for the master disconnect!! It's hard to believe the NHRA continues to defy logic/sound engineering orinciples and require the disconnect on the positive side which makes everything so complex.
I use a 1-wire alternator and as others have noted, the charge wire to the battery must be sufficiently sized. I use a 4 ga wire that is fused (Maxi-Fuse) in the engine bay and also at the rear by the battery so if a short occurs while the car is on or off, or the short is near the front or rear, it will pop a fuse. And I use a CD contactor to power all of the "veh" things up front. It is fed from a separate fused feed coming from the battery that is after the master disconnect.
As for the battery charging, so far, so good. My voltage gauge is fed off the CD contactor so it truly is the voltage running in the system up front in the car. It runs between 12.5-14 volts depending on loads turned on (2 coolant fans, 1 trans cooler fan, headlights, etc).
A simple welding cable quick-connect (disconnected of course) in the batt ground cable keeps everything dead when the car is parked for extended periods.
Bottom line is you use the Ford relay to start the car and only power the big battery cable when in crank mode, you isolate the charging circuit to go only to the battery, and you have a feed wire to run power for your car through a CD contactor. Thinking of it as 3 legs helped me get my head around it!!
BTW...@crackedback knows what he's doing so you won't go wrong there! I used many of his ideas in my build!!
