Noticed that my 2007 Dodge Ram voltage with engine running is 14.75. This is with headlights and Heater on or off. The voltage varies from 14.5 to 14.75 at idle mainly staying at 14.75. The battery looks to be new and had some leakage. It is a Diehard labelled Battery. This doesn’t sound like normal charging voltage to me. Ideas on how to diagnose this.
Alternator charging at 14.75
- Thread starter oilstudent24
- Start date
In my opinion 14.75 volts is a little out of range. Is this measured right at the battery posts?
AGM or flooded?
Try a different volt meter.
AGM or flooded?
Try a different volt meter.
14.7V charge on a regular lead acid battery is right on the edge of excessive gassing, depending on temp and battery state of charge. AGM can go a little higher is my understanding.
Is this directly after start - or does it stay there indefinitely? I agree it would be worth getting your battery tested.
Is this directly after start - or does it stay there indefinitely? I agree it would be worth getting your battery tested.
This is measured at the battery posts. Checked several times. The meter is a cheap one, but in the past has been really close to another meter I’ve used. Nothing close to Fluke brand meters though. I’ve not seen this much brown acid come out of a battery before which has prompted me to check charging voltage. This is a 65 series Flooded Battery.
The following advice is free and you get what you pay for.
I've seen perhaps two batteries with brown acid in them. They were both shot.
Check all related connections and grounds and check voltage again [with a different meter]. If problem persists...
Replace the battery. Can you borrow one for a test?
Monitor the voltage with the new battery. This can be done inside the vehicle using the cigarette lighter/power socket.
If the voltage remains as high as it has been, there is a charging issue.
The alternator is controlled by the engine computer [at least it is in my Dodge of the same vintage]. You want to check the small wires from the alternator to the computer for continuity and corrosion.
I've seen perhaps two batteries with brown acid in them. They were both shot.
Check all related connections and grounds and check voltage again [with a different meter]. If problem persists...
Replace the battery. Can you borrow one for a test?
Monitor the voltage with the new battery. This can be done inside the vehicle using the cigarette lighter/power socket.
If the voltage remains as high as it has been, there is a charging issue.
The alternator is controlled by the engine computer [at least it is in my Dodge of the same vintage]. You want to check the small wires from the alternator to the computer for continuity and corrosion.
I bought a new battery due to seeing the old battery with acid, but didn’t want to fry it until I knew what is going on. I also have a harbor freight resistance battery tester that showed it was good per the numbers. I imagine a load test is more accurate. This vehicle is new to me and don’t know any history on it as far as the battery other than it looked brand new when I bought the vehicle.
The voltage is only slightly off....A battery can take some minor abuse for a short time.
I would put the new battery in and monitor the voltage.
something like this would be convenient...
https://www.aliexpress.us/item/2251801576905307.html?gatewayAdapt=glo2usa4itemAdapt
I would put the new battery in and monitor the voltage.
something like this would be convenient...
https://www.aliexpress.us/item/2251801576905307.html?gatewayAdapt=glo2usa4itemAdapt
I should have mentioned that voltage was at operating temperature. This morning I noticed the voltage was 14.1 while the engine was cold. This is what my Scangauge2 is indicating.
There are two slightly different battery chemistries-- GM's "maintenance free" one takes a few tenths more voltage than the regular version. Might be worth seeing, if you need a battery anyway, if there's an AC Delco replacement in your size, or another legitimate maintenance free one.
My Silverado hit 15.3 in 20-something degree weather. I suspect its smart charging algorithm was exactly that, and that the truck also "knew" I only ran it once a week for five miles. My battery was fine. Your next one might be, as well.
Charging philosophies among automakers vary widely. Euros in particular used to love 13.8V all the time.
My Silverado hit 15.3 in 20-something degree weather. I suspect its smart charging algorithm was exactly that, and that the truck also "knew" I only ran it once a week for five miles. My battery was fine. Your next one might be, as well.
Charging philosophies among automakers vary widely. Euros in particular used to love 13.8V all the time.
This.
Monitor the voltage while driving especially if it's a smart alternator which means the charging voltage can be all over the place.
If it is a smart alternator then assuming the battery is near fully charged you would expect to see a higher voltage on the over run and a lower voltage under acceleration. The controlling algorithm is vastly more complex than that (one example below) but the basic idea is to harvest free charging on the over run although high charging voltages will also occur if the electrical load demands it. Note the very high charging voltage of up to 15.5 volts under certain conditions.
If monitoring shows it's not a smart alternator then 14.75 volts is high but not by much.
The control module enters Charge Mode whenever one of the following conditions is met:
Under WOT conditions and when the fuel rate (sent by the ECM/PCM) is greater than 21 g/S and the throttle position is greater than 90%.
The headlamps are on, low or high beam.
The wipers are on for more than 8 seconds.
The electric cooling fans are on high speed.
The rear defogger is on.
The battery SOC is less than 80%.
When one of these conditions is met, the control module ramps up the voltage slowly to a level between 13.4 to 15.5V (depending upon the mode of operation the system is presently in) at a rate of 8mV to 50mV per second.
The control module enters Fuel Economy Mode when the following conditions are met:
The calculated ambient air temperature is above 32°F.
The calculated battery current is less than 15A and greater than –8A.
The battery SOC is greater than 80%.
The generator field duty cycle is less than 99%.
This mode’s targeted generator output voltage is 13.0V. The control module will exit this mode once the criteria are met for Charge Mode.
The control module will enter Voltage Reduction Mode when the following conditions are met:
The calculated ambient air temperature is above 32°F.
The calculated battery current is less than 2A and greater than –7A.
The generator field duty cycle is less than 99%.
This mode’s targeted generator output voltage is 12.9V. The control module will exit this mode once the criteria are met for Charge Mode.
After the engine has started, the control module sets a targeted generator output voltage of 14.5V for 30 seconds (Start Up Mode).
The control module enters Battery Sulfation Mode when the battery voltage is less than 13.2V for 45 minutes. Once in this mode, the generator battery control module will set a targeted output voltage between 13.9 and 15.5V for five minutes. The control module will then determine which mode to enter depending on voltage requirements.
In RVC Mode, the control module bases the charging voltage on battery SOC, which is estimated during a key-off event every eight hours, after three voltage measurements every 24 hours thereafter, and then monitored constantly while the ignition is on. These voltage measurements are then compared to estimated battery temperature, as battery temperature vs. battery voltage directly corresponds to battery SOC. While the engine is running, the system uses both the battery voltage and estimated battery temperature to determine the battery current in and out of the battery. The control module then regulates the charging voltage to keep the battery above an 80% SOC.
