Voltage Question
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Melting Slicks
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From: Wimauma, FL
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Voltage Question
OK, sorry if this is a stupid question. Took my 18 GS on a 4 hour ride yesterday. I happened to look at the voltage gauge when I started and it was at about 13.5 or so. During the trip later I looked and it was at 13 and sometimes 12.9 or so. Did the same thing on my trip home today. Starts out higher and falls to the 13 mark. Is this the correct operating range? I always thought it needed to be at like 14. Only have 1K on the car. Thanks in advance.
Drifting
Joined: Jun 2015
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From: Lagrange KY
OK, sorry if this is a stupid question. Took my 18 GS on a 4 hour ride yesterday. I happened to look at the voltage gauge when I started and it was at about 13.5 or so. During the trip later I looked and it was at 13 and sometimes 12.9 or so. Did the same thing on my trip home today. Starts out higher and falls to the 13 mark. Is this the correct operating range? I always thought it needed to be at like 14. Only have 1K on the car. Thanks in advance.
Safety Car
Joined: Aug 2012
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This is normal and has been part of most GM cars and trucks for around a decade. The charge management strategy is used to try to maximize fuel efficiency and battery life. Depending upon conditions (and the accuracy of the voltage sensing device) you will see voltage readings varying from the very low 12 volt range to slightly above 15 volts.
When the battery charge is low the alternator output will be increased until the battery reaches a higher state of charge and when there is a heavy draw on the electrical system alternator field excitation will also be increased to provide for the heavier load.
In the owner's manual of most GM vehicles often used for towing (pickups, some SUVs) you will find a note that it may be necessary to turn on the headlights to load the vehicle electrical system sufficiently to ensure an adequate charge for a trailer battery connected to the feed from the vehicle; otherwise if the vehicle battery is sufficiently charged alternator output will keep system voltage too low to adequately charge the connected battery.
The voltage variation appears unusual but there are very good reasons behind what GM is doing with the system.
When the battery charge is low the alternator output will be increased until the battery reaches a higher state of charge and when there is a heavy draw on the electrical system alternator field excitation will also be increased to provide for the heavier load.
In the owner's manual of most GM vehicles often used for towing (pickups, some SUVs) you will find a note that it may be necessary to turn on the headlights to load the vehicle electrical system sufficiently to ensure an adequate charge for a trailer battery connected to the feed from the vehicle; otherwise if the vehicle battery is sufficiently charged alternator output will keep system voltage too low to adequately charge the connected battery.
The voltage variation appears unusual but there are very good reasons behind what GM is doing with the system.
Last edited by NSC5; Sep 22, 2017 at 09:57 PM.
