another delco 10si question

mite-help · Jul 2, 2017

I read the post a couple of days ago about placement of 'sense' wire. I loop it back to output post on alt. the diagram that shows that wire running all the way to battery looks best, especially if bat. is farther away. Then I wonder about the same alt. that is converted to 1-wire. Is that sense feature gone/less sensitive to battery feed-back?

old · Jul 2, 2017

A one wire set up has it so both the sense wire and excite wire are hooked up to work without other wires simple as that and all done internally. As for the 3 wire set up yes one can hook that wire to the battery or to the charge wire on the alternator since either place sees battery voltage

Janicholson · Jul 2, 2017

Almost all alternator conversions are made with either the 6v 10 guge wire to the amp meter/battery, or 10 gauge new wire in its place. Unless the battery is near dead, the charge rate will be modest and voltage drop from the Alt output terminal and the amp meter/battery will be irrelevant. In an automotive/truck application, the accessories and running load may be substantial. Wiring size in the vehicle may be less than 10ga in some places. In these, the use of a direct connect sense to the battery is justified. Pretty irrelevant in a tractor. Jim

John T · Jul 2, 2017

Great question, here's my take which basically agrees with the fine gents below. FYI the voltage sensor circuit is what's used to determine and regulate how much charge is sent to the battery. If the voltage on the alternators big main output stud is the same as on the battery post, it makes no difference where you read it (alternator or battery)

HOWEVER anytime current flows in a non perfect resistive wire there's an I x R Voltage drop so the battery voltage is NOT the exact same as the alternators output BUT UNLESS THE DISTANCE IS GREAT AND/OR THE WIRE IS TOO SMALL AND/OR THERES A BAD CONTACT THERES VERY LITTLE DIFFERENCE which is why it works "about" the same wired to EITHER location. I'm NOT saying how to do it or not do it, I'm ONLY saying absent a long wire or small wire or a bad connection it makes relatively "little" difference.

Obviously if its a ONE wire unit (Big main output stud ONLY, NO other wires leading elsewhere to the exterior) and there are no external voltage sense or excitation circuits you don't need to run a separate voltage sense wire to the battery.

John T

JDEM · Jul 2, 2017

Using the voltage-sensing wire can make a big difference in some cases. I just built a portable gas-driven battery charger. It has a 72 amp Delco 12SI hooked to a 6 horse gas engine. 10 feet of charge cable leads with #2 copper. Alternator was one I had laying around that already had an aftermarket self-excite "one wire" regulator. I tried charging a solar battery bank with it and got pretty fed up. When charging at high amps - it had 14.2 volts at the alternator but only 13.7 volts at the battery bank. The battery bank would never rise above 13.7 volts because the alternator thought it was at 14.2 volts. I finally took the alternator off and stuck in an OEM Delco standard regulator and ran a separate sense wire to the bank with #10 copper. Now it works great and the battery bank comes up over 14 volts.

Obviously on a tractor with a battery three feet away from the alternator, it does not make as big as difference.

another delco 10si question

mite-help

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old

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Janicholson

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John T

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JDEM

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