Ignition/Battery Sources - Help Needed - Impala Tech
Electrical & Wiring Troubleshooting electrical problems

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post #1 of 4 (permalink) Old 02-14-2019, 12:27 PM Thread Starter
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Location: Greenville, SC
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Ignition/Battery Sources - Help Needed

Hello all,
1968 Impala. Let me preface this post by saying that I am a COMPLETE DOLT when it comes to electrical stuff, so thanks in advance for any replies.

This winter I will be adding a few things to my car that were not there before and need to have a better understanding when it comes to wiring it all up. Ground requirements are no problem. The battery and key-on stuff is where I need a little help. The items and their requirements are as follows:

1. MSD Ignition, needs battery and key-on 12V sources
2. Dakota Digital Dash, needs battery and key-on 12V sources
3. Retrosound Hermosa head unit, needs battery and key-on 12V sources
4. Amplifier, needs battery 12V source
5. Holley EFI, needs battery and key-on 12V source

The battery requirements I pretty much get, but I would like to have a cleaner way of connecting all of these to the battery without 5 additional, different ring terminals crammed onto the positive battery terminal. Any better way of doing this other than the multiple ring-terminal idea?

The key-on requirements is where things get really foggy. I only see one spare/empty IGN source in my fuse box. How do I add the additional ones needed safely?

Thanks again.
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post #2 of 4 (permalink) Old 02-14-2019, 01:46 PM
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First thing you need is a new alternator. Not only are you increasing your electrical load beyond the capability of your current alternator to support but the voltage varies wildly as the alternator only charges above 2,600 RPM and doesn't reach rated capacity until it is above 4,200 RPM.

Digital equipment doesn't like the voltage to vary which is why the factory switched over from a on-board battery charger system with the SI series of alternators to a regulated power supply with the CS series of alternators (required for EFI to work). Not only does the CS offer full rated amperage off idle but it never varies in output. Instead of running the car off the battery all of the load is maintained by the alternator.


This requires heavier wiring from the alternator to a distribution bus that will allow you to power all of your devices plus tie the car into the alternators power.


To get your devices to be powered on by the ignition switch you are going to need to include a relay hooked up in series to your ignition switch so that they are only hot when the key is on. Note that MSD ignition box and Dakota Digital dash need an always hot pass through to the battery to work in addition to ignition on hot power; not sure about your amp).

I suggest buying and reading a book on automotive wiring such as Tony Candela's "Automotive Wiring; and Electrical Systems" book.


Big Dave
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post #3 of 4 (permalink) Old 02-14-2019, 02:46 PM Thread Starter
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Thanks Dave. I previously did an alternator upgrade to a Powermaster 100 amp 12SI with the one-wire setup using a 6-guage cable straight to the battery. Will this not be sufficient?
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post #4 of 4 (permalink) Old 02-14-2019, 03:38 PM
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SI doesn't regulate the voltage as well; as a CS. I wasn't aware that they made a one wire SI so it may be a CS. A CS has the fan in the back and blows through to the front (why it has a solid disc installed behind the pulley).

A CS alternator is self exciting. It doesn't require the white and blue field winding wires to get the alternator to work. An SI needs those two wires to power the electromagnet windings to generate power.

Big Dave
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