New to me 02 Excursion V10. I picked it up from Florida where it spent most of its life. Now it’s in Rochester NY. Since it’s gotten cold (low to mid 30s), I’m noticing it’s a bit harder to start, and after starting the battery light comes on and it reads at 15 volts. After a few minutes, it drops to 14 volts and the battery light goes out.

When the temperature here was warmer, it normally read between 13.5 and 14 volts depending on how long it had been running.

Any idea what would be causing the higher initial voltage? The alternator is a newer reman. The battery appears to be new as well, though maybe it’s not enough to deal with the cold?

 

Curious where you are reading the voltage at ?

either way the alternator has an internal voltage regulator that should limit the voltage to 14.4 when it is charging a healthy battery.

my Guess is your battery cables are corroded and the regulator is increasing the pressure/ voltage to overcome the resistance caused by the corroded cables.

 

Voltage reading is coming from torque app and forscan on my headunit. It reads from the obd adapter and ecu. I also have a tire pressure monitor plugged into the 12v port which shows the same 15 volts for 1-2 minutes before going to 14. No corrosion of any kind anywhere. Whole truck including engine bay is almost as clean as it would have been new.

 

The type of corrosion copper wire gets is call oxidation and it is on the inside of the cable protective sheathing, all eire gets it unless of course your vehile has been in outer space where there is no oxygen.

you need to measure the voltage drop of each wire with a Multimeter to determine the level of oxidation.

 

1. You can also find corrosion on the mating surfaces inside the battery cable clamps, that you cannot see unless you take the battery off the cable, Autozone sells a scraper tool that can swab the inner surfaces of the connector, and fits over the battery terminal also to scrape it as well, then they get a much better mating.

2. I have torque in multiple vehicles with both cheap and expensive ODBScan dongles, MX+s, i have never found any of them to be as accurate as an actual multi-meter or high quality cigarette lighter meter. However also note, if you are relying on a cigarette lighter meter, you need to measure at the battery and compare the difference because a lot of **** may be sharing that wires and feeds that feed the power ports, including stuff previous owners have added, and it could cause the reading at the power port to be different than at the battery.

 

I’m using an MX as well since it plays nicer with Forscan. It’s strange that this issue just popped up when it got cold. I have had the battery cables off as I’ve done a bit of work after picking it up this summer. I did plugs/boots/coils as well as a few vacuum lines that had some kinks. I also added a 0 gauge body to battery ground. Replaced all the fluids etc. I also initially replaced the alternator with an upgraded DB electric unit as I felt that the voltage was too low in the summer. (Low 13s). That new alternator ended up being DOA, and I ended up returning it rather than replacing it. The alternator it came with was newer but I suspect that must be the issue. I don’t think I’ve ever seen an over voltage condition that only presented in the cold, and then only for a minute or two.

The current battery says it’s 650 CCA. Maybe that was enough for Florida but not upstate NY?

As for previous owner electronics, I’m not sure what all they had going on, but I assume an aftermarket dvd/sound setup. I spent the better part of a day removing all non oem wiring prior to installing an Android headunit. Picture of that mess of wiring/ hardware attached.

 

I'm a mechanic and also live in Florida. Can't tell you how many times a month I'm replacing coroded cables. I would put a meter directly on the battery and have someone start it up and see what the voltage drop is during cranking. Once started turn on lights (high beams) and anything electrical with a load and see what the max charge from altenator to the batteries. Then check output directly out of alternator. Should be no less than half a volt difference. I've seen where all of that check out good but the excite wire from pcm is chaffed or in general a bad pcm. Not sure on the gasser's but on the diesels, we always change out the pigtail too when we R&R altenator

 

15 volts charging (or even more) is not necessarily unusual, though it probably would be in Florida.

The reason for this is because charging voltages, open circuit voltages, or measuring electrolyte specific gravity, the end point for an individual cell, etc. everything is based on or revolves around temperature. The charts are based on or normalized at 77° F. If the temperature is higher or lower than this figure, then the voltages measured or applied need a correction factor.

As the temperature goes down more juice is needed (over and above what is "normal" at 77 F) to overcome the increased internal battery resistance. A "maintenance free" battery will take 14.8 volts in what's called the absorption phase. Any battery needs about 2 volts above the normal open circuit voltage to reach a full charge. They also like to "rest" at this voltage for a few hours.

At 0° F. the charts tell us to add another full volt to that. North of 15 volts!

Normally people didn't or don't monitor charging voltages in January, so they don't notice things like this. They do notice when their rig doesn't start though. I have a modern gee-whiz bang digital Shumacher charger in my stable, and during charging it displays "12" continuously for the voltage, it is just a dummy gauge during this phase, if you actually were to measure charge voltage at the posts the algorithm goes much higher, as it should.

I guarantee the reason they do this, is simply because everybody has a cow if they see voltages over 12 volts, think the unit is defective, and want their money back. "The battery was bubbling!! OMG!!"

Corrosion in the grounds and connections causes problems because the voltage regulation gets "confused" and thinks the battery is actually fully charged, when it isn't. Normally a battery will accept as much current as you can throw at it, the voltage starts out low, and as the battery starts to get topped off the current tapers off and the voltage rises and battery outgasses moderately. This is normal. A sulfated or neglected battery doesn't accept current the way it should.

14.8 volts continuously at 77° would soon boil a battery dry, in extreme cold though, that would probably barely be a float charge. For the most part we don't notice or need to worry about any of this, it is of interest only to car geeks and cranks, the regulator set point takes all of this temperature stuff into account. Battery chemistry was hashed out 100 years ago. Just do your part and keep cables and terminals and connections at both ends clean, and tight. Top off the battery now and then with your charger, use a float charger in the off season, etc, The battery will last a lot longer than it otherwise would, and it will also give much better performance along the way.

Measure the alternator output when under load - headlights, A/C, heater fan running, spool up the RPM to cruise level of around 2000 or so. Take into account battery charge level, and temperature. Late model vehicles get complicated because they have all sorts of constant draws, battery life or age monitors, and even (sometimes) require a proprietary scan tool to reset if the battery is replaced. Yeesh.