Mattax, this a trunk mount battery with disconnect switch.
OK. And I'll assume the switch must also kill the motor, and grounding out the engine is not allowed.
As a street car, yea, I've got a full complement of other functional items in addition to the ignition; all light systems (head, tail, dome, dash, ash, glove, brake, hazard, turn signals), hvac, radio, fuel pumps. May consider O2 sensors or efi in the future as well. Can't foresee ever doing power windows or seats.
Fuel pump, EFI are the big ones that might benefit from a strategy different than stock. These can draw down the battery when the alternator is not running (start) or not capable of providing the power demanded.
Lets say an alternator is used that can produce 280 Watts when the engine is at 650 rpm. This means it can provide up to 20 amps at 14 Volts.
I'm not sure what the 'turn on' speed is for a 1-wire, but for sake of example, lets assume its self powering at 650rpm and the field is drawing off 2.5 amps.
A solid state ignition maybe draws another 2.5 amps.
That leaves 15 amps for everything else.
Turn on the lights and that's around 14 amps,
Step on the brakes and now the alternator can not supply the power needed. System voltage drops and when it gets around 12.8 Volts, the battery becomes the power source with highest voltage.
This was somewhat tolerable with mechanically supplied fuel, since it only happened briefly at stop lights and stop signs.
But with more equipment, this is situation will occur more frequently. The typical stock systems through '75 assumed the power would almost always come from the alternator and the battery would only need minor recharging.
As a '74, it also has all the seatbelt interlock stuff that I'm working out of the system and replacing with the clutch start circuit. So when you say relay, something capable of the full amp load of the balance of the system plus a margin or the total alt output? In that case, would I still want the power lead from the starter to the OEM relay?
Can't help with the interlock.
When I say full amp load, I mean the equipment that will be calling for power.
I don't know if it makes a difference whether an second wire is run all the way from the cut off switch to the OEM Relay stud, vs connecting it as shown in the drawing.
I'll work on a drawing but post this now, as the board may shut soon.
