High charging voltage

[CoastyAV8R]

I've noticed that since I bought my truck a month ago the charging voltage is always around 14.8-15 volts, I have a digital meter I plug into the cigarette lighter and I verified it's accuracy with a voltmeter. I keep the truck on a trickle charger and had the batteries tested and they are good and the truck has no issues starting and the lights don't flicker or any other unusual electrical anomalies. The batteries don't get hot but I'm concerned that the voltage is always that high.

I'm going to clean the grounds for both batteries today, anything else I should be looking at?

 

[dieselshadow]

I’d be checking your crossover cable. These are notoriously bad for causing issues such as this.

 

[CoastyAV8R]

I’d be checking your crossover cable. These are notoriously bad for causing issues such as this.

I assume you mean disconnect both ends and check for resistance? Any numbers I should be looking for or anything above continuity consider it bad?

 

[dieselshadow]

They’ll corrode internally and cause high resistance. The computer is “looking” at one battery while the alternator charges the other. The crossover cable is supposed to keep things balanced. A quick and easy resistance check may not show the problem.

 

[DavidC]

For a 6' cable being 1/0 the actual resistance is
0.000717
Make sure to touch the meter leads together to know the resistance of those to subtract from the reading. So, depending on how many digits your meter shows it will be .00 to .01

 

[Ozymandias]

14.8-15.2 is perfectly fine for your Truck during wintertime, nothing wrong with it. We all see that.

You'll see lower voltages during summer, around 14.2-14.5

 

[Tuesdak]

charging voltage is always around 14.8-15 volts

This is completely normal for the Dodge Ram temperature compensated charging system. Temperature sensor is under a battery.

IMO it's a better system than GM that senses temperature in the alternator. Bottom line is the voltages are higher than what one would be used too with GM stuff.

 

[CoastyAV8R]

For a 6' cable being 1/0 the actual resistance is
0.000717
Make sure to touch the meter leads together to know the resistance of those to subtract from the reading. So, depending on how many digits your meter shows it will be .00 to .01

Great info. Has anybody ever seen the battery temp sensor on the drivers side go bad? In my reading it lets the ECM know if the batt temp is high and will reduce the voltage which obviously isn't my problem but I'm curious what the symptoms are if one were to go bad.

 

[CoastyAV8R]

14.8-15.2 is perfectly fine for your Truck during wintertime, nothing wrong with it. We all see that.

You'll see lower voltages during summer, around 14.2-14.5

No kidding? I've had this plug in voltmeter in a few vehicles and I guess I'm just not use to seeing that high of voltage continuously. I'm still going to go clean all my connections as it's probably something that I should look at just to be sure.

 

[Tuesdak]

For a 6' cable being 1/0 the actual resistance is
0.000717
Make sure to touch the meter leads together to know the resistance of those to subtract from the reading. So, depending on how many digits your meter shows it will be .00 to .01

A better way is to measure battery voltage: as resistance of a large cable is almost impossible to measure with a handheld meter. Are the voltages the same across each battery with engine running? Measure voltage from one positive battery terminal to the other positive battery terminal: this measures voltage across the cable. Yes, 0.01 V range matters. You will have 6 or more amps on the cable with the engine running so voltage will tell you it's resistance. But we are looking for a voltage reading that matters in this 0.01 range.

 

[CoastyAV8R]

A better way is to measure battery voltage: as resistance of a large cable is almost impossible to measure with a handheld meter. Are the voltages the same across each battery with engine running? Measure voltage from one positive battery terminal to the other positive battery terminal: this measures voltage across the cable. Yes, 0.01 V range matters. You will have 6 or more amps on the cable with the engine running so voltage will tell you it's resistance. But we are looking for a voltage reading that matters in this 0.01 range.

I just added that test to my list of what to do today. I have 4 voltmeters so I'm sure one of them will be able to span the gap between the two batteries.

 

[Ozymandias]

Great info. Has anybody ever seen the battery temp sensor on the drivers side go bad? In my reading it lets the ECM know if the batt temp is high and will reduce the voltage which obviously isn't my problem but I'm curious what the symptoms are if one were to go bad.

Very rare and the truck gives you a fault code, if it fails the trucks volt meter goes to 12V and it sets off the buzzer.

You could check that by disconnect it, it's under the drivers side battery, accessible by taking out tge wheel well.

But like said, your Truck works perfect, there is nothing wrong with it or to worry about.

 

[Ozymandias]

No kidding? I've had this plug in voltmeter in a few vehicles and I guess I'm just not use to seeing that high of voltage continuously. I'm still going to go clean all my connections as it's probably something that I should look at just to be sure.

Yeah, the Diesel has an aggressive charging algorithm to keep up with the demand of the grid heater.
That's why some batterys fail prematurely as they are not designed for such high charging voltages.
Always check the batterys data sheet before buying then.

 

[Axekicker]

This is the voltage my 2004.5 runs in the winter when fully warmed up and driving across town.

In the winter it tops out at 14.9 to 15 volts on cold days and when it's 115deg/F in the summer, it drops to low 14's.
Two volt meters...one for each Cat-bat.

 

[KParsons]

This is the voltage my 2004.5 runs in the winter when fully warmed up and driving across town.
View attachment 126626
View attachment 126627
In the winter it tops out at 14.9 to 15 volts on cold days and when it's 115deg/F in the summer, it drops to low 14's.
Two volt meters...one for each Cat-bat.

 

[Ozymandias]

?

 

[CoastyAV8R]

This is the voltage my 2004.5 runs in the winter when fully warmed up and driving across town.
View attachment 126626
View attachment 126627
In the winter it tops out at 14.9 to 15 volts on cold days and when it's 115deg/F in the summer, it drops to low 14's.
Two volt meters...one for each Cat-bat.

I'm in Central Oregon at about 4500 feet so it's quite a bit colder, I cleaned everything up (grounds, connections) and it's still around 14.9. Hopefully when it gets above freezing I'll see voltages similar to yours.

 

[Ozymandias]

I say it again - your Truck is in perfect working condition, it does what it is supposed to do - stop worry about that point. There is nothing wrong with it.

 

[JKosten]

I assume you mean disconnect both ends and check for resistance? Any numbers I should be looking for or anything above continuity consider it bad?

Also physically feel the crossover cable. It should be slightly flexible. It is it stiff, the cable has corrosion within the jacketing. Unfortunately common.

If you have a corrosion present it will effect the charging system, as the generator is connected to the passenger side (aux) battery, and then charges both batteries and powers the TPIM through the crossover cable.

 

[AEdelheit]

I'm in Central Oregon at about 4500 feet so it's quite a bit colder, I cleaned everything up (grounds, connections) and it's still around 14.9. Hopefully when it gets above freezing I'll see voltages similar to yours.

Im in Central Oregon as well and see 14.5-14.9 year round, have replaced the crossover cable and ensured all connections are tight and clean just how these trucks are. I also had a broken battery temp sensor and did not notice any difference after replacing it.