charging system voltage.

[2003silverado]

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.

[2003silverado]

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]

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.

[BurbMan]

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]

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.

[2003silverado]

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]

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

[2003silverado]

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]

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

[BurbMan]

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]

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]

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.

[BenK]

Hey Turtle...being older than you...excuse is old grey matter... :B

[Turtle_n_Peeps]

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

I agree with Ben. Have it checked out.

[BenK]

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