Alternator B+ to Starter Relay or Battery, any difference

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Eworth

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Hello,
I am upgrading wiring and also installing a larger alternator, a 90 amp from a 1990 Dodge 5.2 in my 64 Dart with a 318.

Also has HEI ignition upgrade if that changes anything here..

Does it matter where I run the B+ 6 gauge alternator wiring? Either Starter Relay or Battery positive?

Also, I know that this much amperage shouldn't go to the ammeter. By running the wiring directly to the Starter Relay or Battery, am I bypassing the Ammeter like I want to?

Thanks for all advice.
 
Best thing is to "start" by reading the MAD article. I'm assuming? your wiring? is largely factory. No you do not want to run such a large alternator through the factory ammeter, but "worse" is running it through the factory bulkhead connector

http://www.madelectrical.com/electricaltech/amp-gauges.shtml

Once you get the ammeter / bulkhead bypassed, then it doesn't matter too much, either starter relay or battery, whatever is easiest to make a good connection.

Be sure to oversize wiring on "one wire" setups No8 is not too large. Three parallel no 10 would work as well. You should fuse it close to the battery
 
The battery helps filter the alternator output. There will be more voltage ripple for electronic devices powered from the starter relay stud, if the alternator feeds that point. If the alternator feeds the battery, filtering is improved due to low impedance path, however the ammeter circuit is compromised.

The ripple can be measured with meter on AC volts, typically use 2 VAC range.
 
KitCarlson said:
The battery helps filter the alternator output. There will be more voltage ripple for electronic devices powered from the starter relay stud, if the alternator feeds that point. If the alternator feeds the battery, filtering is improved due to low impedance path. however the ammeter circuit is compromised.

The ripple can be measured with meter on AC volts, typically use 2 VAC range.
Click to expand...

This is EXACTLY the information I was looking for. THANK YOU !!!
 
KitCarlson said:
The battery helps filter the alternator output. There will be more voltage ripple for electronic devices powered from the starter relay stud, if the alternator feeds that point. If the alternator feeds the battery, filtering is improved due to low impedance path, however the ammeter circuit is compromised.

The ripple can be measured with meter on AC volts, typically use 2 VAC range.
Click to expand...

This is also going to depend on the size and length of wire between the relay and battery, assuming the loads and the alternator are hooked to the relay
 
67Dart273 said:
This is also going to depend on the size and length of wire between the relay and battery, assuming the loads and the alternator are hooked to the relay
Click to expand...

That is very true, and might not be an issue with #6. Use of the meter at the locations will give the numbers. I would think a 200 mV RMS or less would acceptable, where electronic loads are served.
The electronic loads should be off. They filter too, but too much ripple current may fail capacitors.
 
Take a moment and think how the factory wired it, straight from alternator to wired splice under dash. Yes, the battery is a great buffer for the system.

If you have a bunch of stuff that is pulling power and go direct to battery, make sure the jumper wire from battery to starter relay is appropriately sized. That wire now becomes your lifeline to power the entire car.

Going alt to the starter relay removes the battery jumper wire from the equation when the engine is running.
 
crackedback said:
Take a moment and think how the factory wired it, straight from alternator to wired splice under dash. Yes, the battery is a great buffer for the system.

If you have a bunch of stuff that is pulling power and go direct to battery, make sure the jumper wire from battery to starter relay is appropriately sized. That wire now becomes your lifeline to power the entire car.

Going alt to the starter relay removes the battery jumper wire from the equation when the engine is running.
Click to expand...
What you say is logical and accurate from a DC perspective, but the circuitry has DC and AC components. The AC component introduced by the alternator, will flow as reactive current to the battery or other low impedance source such as bulk capacitance in power supply of electronic loads. With reactive current, there are associated voltage drops in the resistance, and inductance of circuits. The closer to alternator, more ripple, closer to battery, or bulk capacitance, less ripple. The lower the wiring impedance, the less ripple.

When the original system was designed, EFI, HEI, nor modern electronic loads such as digital amplifiers were common. New vehicles have a much different power circuit designs. Early on Mopar replaced mechanical regulators, with electronic ignition, to reduce noise improve regulation, for ECM reliability. The 5 pin ignition ECM, resistor and zener was replaced with a series pass linear regulator, in the 4 pin ECU for further improvement, and elimination of dual ballast. A long series of changes in automotive evolution.
 
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