battery volt between 13-13.8
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Junior User
Joined: May 2014
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battery volt between 13-13.8
Is this a normal, I have a 07 f250 6.0l and just hooked up my tuner and this is what it is showing, batteries are 2 yellow top optima about 3 yrs old, original alternator, load on or nothing on while driving shows 13.2-13.8, and my ficm stays pretty steady between 47-48.5, is my alternator starting to go, only reason I ask is I thought while driving it should be around 14v
Lead Driver
Joined: May 2014
Posts: 6,545
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From: Virginia Beach VA
The alt outputs what's needed to maintain amperage draw... those numbers look good to me. Less than 13.2 loaded, I'd start to look for a cause. Batteries want to be 12.6-12.8 volts, those numbers show a charging alt.
Token Redneck
Joined: Jun 2007
Posts: 9,337
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From: Breckenridge, TX
Use a DVM and test voltage from the alt stud to alt case, then the alt stud to the passenger's battery positive stud, and then between the two positive studs on the batteries. You should see a slightly higher voltage at the the alt itself than through the OBDII port, then <.1-.2V drop across each of the charging wires. If you're getting large drops you might be having some kind of wiring issue, but .3-.4V between the alt and OBDII port isn't unreasonable.
Elder User
Joined: Aug 2006
Posts: 642
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From: Olathe, KS
13.2 is lower than I like personally, but is in range. You might also do a ground check via the meter while there. Alt to batt neg, alt to frame, battery neg to frame, battery neg to batt neg. If you see resistance, clamp on some jumper cables between the offenders then check system voltage and ohms again. If better you know where to correct grounds or add a ground strap across there.
Senior User
Joined: Dec 2008
Posts: 144
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From: Deerfield, VA
The PCM in conjunction with the voltage regulator regulates that charge number. Mine starts at 14.2 and then settles down to 13.6 to 13.8 after 20 minutes. Without load their is no need to "cook" batteries. If you can hold above 13.2 volts with full accessories on (headlights, AC, high blower) you are OK. Charge rate also gets lower quickly with good battery health. Anyone running around charging @ 14+ continually usually has batteries that are on their way out.
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speedofmouth
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