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charging system voltage.

2003silverado
Explorer II
Explorer II
My truck is a 2012 Silverado 2500hd 6.0 liter gas with 40,000 miles that I've owned since new. A couple months ago I notice that the voltage gauge was running quite a bit above the 14 volt point in the middle of the gauge. Since then it has been between that point and just a hair above the 14 volt center point. When I got home today I noticed it was at the high spot again so I left it running and fetched my volt meter and 15.12 volts at the battery.

Is that too high? Seems like I've always known charging systems to run around 14 volts. But it also seems like as computerized as these newer vehicles are I would get a message on the dash of too high of voltage. Wondering if I have a faulty voltage regulator.
14 REPLIES 14

2003silverado
Explorer II
Explorer II
Temps yesterday when I read the 15.1 volts were in the 40 degree range. The last 6 days have been in that range, prior to that and for about the last month we have been extremely cold, as much of the country was. Highs in the single digits and lows down to -15.

I popped the battery terminal connections off this am and all looked like new. I used of sand paper on them just because I had them off, but not expecting miracles due to the very clean and shiny condition prior. I guess I'll just keep an eye on it and mention it to the dealer if the condition persists into the 50s and above.

Incidentally, the charging system wouldn't be covered under the power train warranty would it?

Thanks for all of your responses.

APT
Explorer
Explorer
GM uses a variable alternator voltage in many late model vehicles. Higher voltages at colder ambient temps in order to handle the extra electrical loads uses in colder temps as well as charge quicker from higher current required to start the engine.
A & A parents of DD 2005, DS1 2007, DS2 2009
2011 Suburban 2500 6.0L 3.73 pulling 2011 Heartland North Trail 28BRS
2017 Subaru Outback 3.6R
2x 2023 Chevrolet Bolt EUV (Gray and Black Twins)

BurbMan
Explorer II
Explorer II
Actually the site says 14.8-15.0, which is pretty close to what the OP measured at 15.1. Charging voltages over 14.5 are OK if the ambient temps warrant such, and since the OP lives in Michigan and it's March, it is certainly possible. I wouldn't expect to see over 14.5 at all in your neck of the woods.

Modern voltage regulators are 100% solid state and like anything else electronic they tend to be binary: either it's working correctly or not at all. Regulators will fail either full off, where no battery charging is taking place, or full on where the voltage is completely unregulated and cooks the battery in short order.

Turtle_n_Peeps
Explorer
Explorer
According to this site any battery out there does not like to see over 14.8 volts. Pretty much what I was taught in school during the dinosaur age. 🙂

A lead acid is a lead acid no matter what decade it was made in. I know one thing; I would not want to see a "continuous" charge rate of over 14.5 volts for any length of time for anything I own.

PS: I've seen one cell short and spike voltages like that. Let us know what you find out.
~ Too many freaks & not enough circuses ~


"Life is not tried ~ it is merely survived ~ if you're standing
outside the fire"

"The best way to get a bad law repealed is to enforce it strictly."- Abraham Lincoln

2003silverado
Explorer II
Explorer II
Battery is original with the truck and it has top posts. And I'm guessing its a flooded lead acid battery, not agm. I am also sure it has never been dead or close to dead. I will check the posts tomorrow to see if there is any corrosion. Only other thing I can think of is the truck is used for commercial snow removal and we run a fairly heavy (western wideout) plow on it and an all electric v-box salt spreader so we place a fairly heavy demand on the charging system. The truck has the plow prep package with the high output alternator so it should be designed to handle the added load.

If the terminals are clean is the consensus that 15 volts isn;t too high? And do these trucks have safeguards or warnings against continuous high voltage?

BenK
Explorer
Explorer
Oh...how old is the battery? It maybe cooked if original...especially if it has been
drained below 50% and if more than once, replace it. It will NEVER hold a full
charge again.

Flooded or AGM? Assume side post, right?

Bryan's comment of the terminals is a very good one

'Good' electronics should have a voltage supply capable of managing over/under
voltage, but spikes might get through
-Ben Picture of my rig
1996 GMC SLT Suburban 3/4 ton K3500/7.4L/4:1/+150Kmiles orig owner...
1980 Chevy Silverado C10/long bed/"BUILT" 5.7L/3:73/1 ton helper springs/+329Kmiles, bought it from dad...
1998 Mazda B2500 (1/2 ton) pickup, 2nd owner...
Praise Dyno Brake equiped and all have "nose bleed" braking!
Previous trucks/offroaders: 40's Jeep restored in mid 60's / 69 DuneBuggy (approx +1K lb: VW pan/200hpCorvair: eng, cam, dual carb'w velocity stacks'n 18" runners, 4spd transaxle) made myself from ground up / 1970 Toyota FJ40 / 1973 K5 Blazer (2dr Tahoe, 1 ton axles front/rear, +255K miles when sold it)...
Sold the boat (looking for another): Trophy with twin 150's...
51 cylinders in household, what's yours?...

2003silverado
Explorer II
Explorer II
Thanks guys. I drove it again this afternoon and it was down to about 14.6. My main concern was frying a computer due to too high of voltage but seems like its not too high based on your thoughts.

I will keep an eye on it and mention it next time it's in for service. Again, thanks.

ScottG
Nomad
Nomad
Times have changed and that voltage is fine especially if it's not hot out.

BurbMan
Explorer II
Explorer II
The regulator may allow voltage over 14.6 depending on what it senses state of charge to be...and newer regulators also compensate for temperature....since you noticed the higher voltage a few months ago, then it was normal at 14.6 for a while, now it's high again...what were the conditions? On a cold day, the regulator may allow 15.8v in charging current to the battery, on a hot day it may taper it back to 13.5v.

I would keep an eye on it for a bit before I'd drop a benjamin for dealer diagnostics. Good articles here and here.

time2roll
Nomad
Nomad
Voltage should drop when the days get warmer.
Otherwise if it sticks over that 15 mark for an extended period I would take it in.

carringb
Explorer
Explorer
It wouldn't hurt to start with the basics: Clean the battery terminals

If the terminals have extra resistance due to corrosion, the voltage regular (which is probably internal to the PCM, but with an extra sensing wire from the battery) can see low voltage and attempt to apply full power to charge the battery back up, but since it's not actually discharged, voltage can peak above the target charge voltage.
2000 Ford E450 V10 VAN! 450,000+ miles
2014 ORV really big trailer
2015 Ford Focus ST

BenK
Explorer
Explorer
Hey Turtle...being older than you...excuse is old grey matter... :B
-Ben Picture of my rig
1996 GMC SLT Suburban 3/4 ton K3500/7.4L/4:1/+150Kmiles orig owner...
1980 Chevy Silverado C10/long bed/"BUILT" 5.7L/3:73/1 ton helper springs/+329Kmiles, bought it from dad...
1998 Mazda B2500 (1/2 ton) pickup, 2nd owner...
Praise Dyno Brake equiped and all have "nose bleed" braking!
Previous trucks/offroaders: 40's Jeep restored in mid 60's / 69 DuneBuggy (approx +1K lb: VW pan/200hpCorvair: eng, cam, dual carb'w velocity stacks'n 18" runners, 4spd transaxle) made myself from ground up / 1970 Toyota FJ40 / 1973 K5 Blazer (2dr Tahoe, 1 ton axles front/rear, +255K miles when sold it)...
Sold the boat (looking for another): Trophy with twin 150's...
51 cylinders in household, what's yours?...

Turtle_n_Peeps
Explorer
Explorer
I was always taught in school 14.2 was the magic number for a 12v system.

I agree with Ben. Have it checked out.
~ Too many freaks & not enough circuses ~


"Life is not tried ~ it is merely survived ~ if you're standing
outside the fire"

"The best way to get a bad law repealed is to enforce it strictly."- Abraham Lincoln

BenK
Explorer
Explorer
All rechargeable battery's needs a voltage *ABOVE* their working or storage voltage

Otherwise they won't charge

The rate of charge is factored by both the voltage and amperes (inter-related)
and the higher the voltage, the faster...but can be too fast as the chemical
change from crystal will cause the chemicals to overheat and out-gas

Out-gassing is a VERY bad thing for any battery

There is a voltage regulator somewhere in your alternator circuit that maintains
the optimal voltage...normally 14.6 VDC

Have your mechanic check it out
-Ben Picture of my rig
1996 GMC SLT Suburban 3/4 ton K3500/7.4L/4:1/+150Kmiles orig owner...
1980 Chevy Silverado C10/long bed/"BUILT" 5.7L/3:73/1 ton helper springs/+329Kmiles, bought it from dad...
1998 Mazda B2500 (1/2 ton) pickup, 2nd owner...
Praise Dyno Brake equiped and all have "nose bleed" braking!
Previous trucks/offroaders: 40's Jeep restored in mid 60's / 69 DuneBuggy (approx +1K lb: VW pan/200hpCorvair: eng, cam, dual carb'w velocity stacks'n 18" runners, 4spd transaxle) made myself from ground up / 1970 Toyota FJ40 / 1973 K5 Blazer (2dr Tahoe, 1 ton axles front/rear, +255K miles when sold it)...
Sold the boat (looking for another): Trophy with twin 150's...
51 cylinders in household, what's yours?...