maximum voltage on dash readout

[Obscurity]

I seem to be getting anywhere from 12.1V to as high as 15.0V (mostly when coasting). What is the highest I should see? When I took the jeep in they confirmed that it was way to high until they had it for almost a month and now they say 15 is just fine. I don't feel like I am getting a the straight story

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[melendez69]

There are a few factors involved, namely outside temperature, battery health/life, etc. I think anything higher than 15v would be a bit much. It's unusually cold down here in NC, and I'm currently around 14.2 - 14.6 on new batteries.

There are quite a few threads on this topic.

 

[58Willys]

You a smart charging system/variable output alternator. What you are seeing is normal.

 

[gato]

I've only on one occasion (very cold and a few starts in a row) saw 14.6. Most of the time it tops out at 14.4, on rare occasions 14.5. I'd be concerned above 14.6 on my Jeep, just because I have never seen it.

After I did the aux battery bypass and changed the battery I have been watching it as a hawk from summer to winter, so I have seen it in every condition. When you drive for a long time between starts you see high 13.x. When you do a short trips with more restarts you see 14.x.

 

[Rogersocal]

When its 40 outside i see 14.5, I have seen 14.7 and it was 32 out. Seems pretty normal to me.

 

[drrags]

15 volts is an indication that your battery is going bad. There are lots of reasons why your battery is at the end of its life, such as, lots of short commutes, age of the battery, completely discharged a few times, etc. The charging system is giving everything it's got to fully charge it but it can't keep up. You can test this by using a battery charger and charge it up all the way. Then, take it for a drive. You'll probably see the voltage is in the high 12s but eventually it will go back to 14.9 or 15.0. Or, your home battery charger may not even be able to fully charge it. You can take it to O'Reilly's or some place and have the battery tested, which is what I recommend as a 1st step.

 

[alphawolff]

I seem to be getting anywhere from 12.1V to as high as 15.0V (mostly when coasting). What is the highest I should see? When I took the jeep in they confirmed that it was way to high until they had it for almost a month and now they say 15 is just fine. I don't feel like I am getting a the straight story

Something I've been noticing recently as well. I've been seeing my voltage spike to 14.8v during low speed coasting when the jeep is cold. Happens randomly and not very consistant. When it did occur I checked afterward and it threw a stored voltage too high DTC in the FFCM, but otherwise no issues.

Generally it should never go above 14.4v with the AGM batteries, but I've seen 14.6 on occasion. Anything above that is overcharging. I'm not sure what's going on or why, but if it doesn't go over 15 I wouldn't worry about it. Maybe check battery SOH/SOC? Mine were at 77% when I checked after I noticed it.

I didn't have the scan tool on me to check when it was occurring. If you have access to one verify the target charging voltage and voltage sense data readouts in the PCM are within 0.1v of each other when the problem occurs. If the voltage sense is jumping 0.2v over the target voltage then I'd say we have a batch of defective alternators

 

[WranglerMan]

I've been seeing 14.7 for the first hour of driving on brand new Full River batteries and they test fine using a Motopower tester but its been very cold here in the midwest with temps below zero, after driving for awhile it slowly drops.

 

[Jebiruph]

I've spent a lot of time monitoring my voltage over the past 7 years. A short commute has led to a lot of 14.7 V charging, but since the last firmware update for the manual transmission recall, I'm seeing a lot of 15.1 V charging.

 

[Doug G]

I've been seeing 14.7 for the first hour of driving on brand new Full River batteries and they test fine using a Motopower tester but its been very cold here in the midwest with temps below zero, after driving for awhile it slowly drops.

I just replaced the Main and Aux batteries with Odyssey batteries. While driving I read 14.7V even after driving 30 miles. Outside temps 20s to 40s.

This does not seem normal.

 

[Mguy]

I seem to be getting anywhere from 12.1V to as high as 15.0V (mostly when coasting). What is the highest I should see? When I took the jeep in they confirmed that it was way to high until they had it for almost a month and now they say 15 is just fine. I don't feel like I am getting a the straight story

15V is not consistent with good voltage regulation for charging an AGM and if that's what the system shows regularly there should be concern. Even at very cold temperatures, that's too high. With our JLs, there seems to be different voltages with different engine/hybrid electric systems at different stages of vehicle operation. Additionally, designing circuits for AGM start batteries seems to be an art as much as a science. There isn't precision in hitting target voltages, and sometimes there is lag time.

Also, 12.1V is too low for engine charging, but could be an appropriate system reading for some engine setups during some stages of vehicle operation. It could be an indiction of intentional low charging load for increased power to the wheels. For reference, my alternator/manual transmission equipped 3.6L, which has just a "small" start battery and virtually no need for charge load reduction, never see less than 12.8V or so when the engine is on. What's your engine system?

Unfortunately, us owners have limited access to information about the voltage regulation in our Jeeps. Maybe ask a dealer if voltage regulation can be reprogramed, or otherwise test the electronic module which provides regulation?

 

[Mguy]

I just replaced the Main and Aux batteries with Odyssey batteries. While driving I read 14.7V even after driving 30 miles. Outside temps 20s to 40s.

This does not seem normal.

It could be normal for your driving habits and engine/charging system. Voltage regulators for 12 V batteries (not just for Jeeps) typically start very high and it takes a long time, hours, for an AGM to reach full, even if only discharged to around 80% or 90%. For instance, 30 miles (even taking an hour or so) every day, with some engine-off loads, would likely be insufficient charging for at least some JL models, particularly those with aux 12V batteries.

 

[Obscurity]

15 volts is an indication that your battery is going bad. There are lots of reasons why your battery is at the end of its life, such as, lots of short commutes, age of the battery, completely discharged a few times, etc. The charging system is giving everything it's got to fully charge it but it can't keep up. You can test this by using a battery charger and charge it up all the way. Then, take it for a drive. You'll probably see the voltage is in the high 12s but eventually it will go back to 14.9 or 15.0. Or, your home battery charger may not even be able to fully charge it. You can take it to O'Reilly's or some place and have the battery tested, which is what I recommend as a 1st step.

I thought of that however its a 24 and the battery has already been replaced once trying to diagnose another issue related to O2 sensors

 

[Obscurity]

. Maybe ask a dealer if voltage regulation can be reprogramed, or otherwise test the electronic module which provides regulation?

The answer seems to always be its "operating as designed"

 

[THAW]

From a Stellantis document regarding RAM alternators and charging:

"The eTorque engines use a DC to DC convertor to charge the 12V system.
...
Voltage set point 13.3V-14.7V depending on temperature."

Obviously, that voltage range is not necessarily directly and precisely applicable to JLs - especially those with traditional alternators. But, the parameters are perhaps broadly indicative of target voltage bounds.

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