Battery Voltage reading? What is normal?

wwood

New member
On the vehicle info screen on the Jeep dash (EVIC) there is a tab for a Battery Voltage gauge.
On our JLUR this gauge reads 14.2-14.7 volts consistently when driving at normal highway speeds.
Is that reading normal, wondering what reading other guys are seeing?
Seems too high to me to be running over 14v all the time.
I assume this gauge is actually reading the alternator output but it seems odd that it would read that high all the time since the battery is always fully charged.
When I read the voltage across the battery terminals with a volt meter when the engine is not running the voltage is 12.6v, which is normal for a full charge.
We have no problems or error messages but I am wondering if the alternator is putting out too much juice which could kill the batteries.
Thanks for any ideas.
 

SouthCo

New member
I don’t own a Jeep (yet) but I know on my pickup the alternator puts out in the 14v range when cruising and it’s normal. It does fluctuate some at times. The alternator does more than just charge the battery/batteries (my truck has two) so it needs to output higher than 12v. So I’m betting your Jeep is operating normally.

I’m sure a knowledgeable Jeep person will confirm or correct me if Jeeps are different.
 

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doubletapdaddy

Caught the Bug
I was trying to dig up an older thread regarding the same topic, but have been unable to find it. If I remember correctly what you describe is completely normal.
 

JTCO

Meme King
Hopefully Scott chimes in because I bet he knows the exact specs. But most vehicles on a 12V system have charging voltage in the low 14s. You should be fine. If you turn on your AC and headlights, you can watch it drop.
 

wwood

New member
Thanks guys, if any of you get a chance take a look at the battery voltage gauge on your Jeep and let us know what it reads during normal driving. Thanks.
 

Wranglerman

New member
I went thru this same issue months ago, when I first got my JLU Sahara the EVIC displayed voltage ran 12.7-14.2 and anything in between but then I installed a Tazer and several months after that the voltage crept up to 14.4-14.6 all the time and I figured that was right as I’m old school and seeing 14+ is supposed to be normal when the engine is running but then I had to remove my Tazer to take my Jeep in for a TSB to be applied and once I removed it the ESS screen on the EVIC said Start/Stop not ready battery charging so I brought that to the dealers attention and they advised seeing 14+ all the time is not normal so they started doing some testing and they found the main battery was bad after it was tested using a GR8 tester and they replaced it

Well after I got it back I was thinking all sorts of stuff like did the Tazer cause this issue, did I leave something on, did I just have a bad battery ? Well I got real curious so I started digging and looking at the duel battery system on the JL and it’s actually a pretty complex deal as it uses two batteries that are separated by a control relay and then there is an IBS that comes off the main negative and all of this goes back to the ECU so from digging and digging and talking with several FCA techs at the dealer this is what is supposed to happen, when you start your JL the IBS ( intelligent battery sensor ) reads the voltages off the batteries as they are connected together but separated by a charging relay that disconnects when ESS is engaged so the JL can pull voltage from the ESS battery and depending on what voltage it sees it tells the alternator to charge at a certain rate to bring the batteries to the 12.7 range and the closer you are to that the lower the displayed EVIC voltage will be and once the batteries are charged what is normal is supposed to be in the 12.6-12.9 range while running and if let ESS engage lots of times that voltage will be higher but it should again charge at a lower rate the longer you drive.

I thought this was really odd but again as it was explained to me and from what I gathered from my limited research is the reason for this “smart charging “ is by charging at only the required lower rate it’s supposed to help battery life by not constantly charging the battery at 14+ volts and also normal behavior is supposed to be as you break or just let off the gas the voltage will ramp up to do a quick charge so to speak and the reason is does this during deceleration is it’s supposed to help mileage by not putting a load on the alternator during normal driving

So with all my rambling he is a vid of what my JL voltage does and the dealer service folks tell me it’s 100% normal


I also did 14 days of daily voltage testing with and without a Tazer installed and can post those results if you guys are interested
 

13_gecko_rubi

New member
Like many others said that is normal. When the alternator is running full output it will be up in the 14s. As your battery charges if you don't have high electrical loads it can drop into the high 12s/low 13s. The JL for fuel economy will keep the battery at full charge using state of charge algorithms and the IBS mentioned above and will try to put out as little alt power as needed. There is a huge range of what you could see on that screen. If you have no warning lights or messages all is well.

Sent via....
 

Wranglerman

New member
You've got too much disposable time on your hands. Please come over and install my lift post haste.

You are correct I do sometimes have way to much time on my hands and my OCD gets the better part of me, when I first started checking voltsges I was doing it incorrectly as I did not have the main and ESS battery separated I started reading those voltages separately and to make it easier I put a 8mm wingnut on the ESS negative

Here is some possible useful info for those interested, as you can see the Tazer being left plugged in or unplugged had little affect on voltages but some have reported that once the Uconnect system goes to a resting mode where power is supposed to be off something is waking it back up thru the Canbus and this has happened to me on more than one occasion, I have gotten out of my JL and shut all doors and locked it and then the EVIC sisplay and gear shift indicator power down but then come back on and stay on and the way it’s supposed to be is once the dome light shuts off the rest is suppOsed to rest within a minute or so and with me I have had those lights stay on and by on I mean over an hour and to resolve I just open and close any door and this has happend with and without the Tazer installed, I have checked and checked and can not determine what causes this and the dealer does not have a clue


Battery Voltage Tests with Tazer JL
2018 Wrangler JLU Sahara
Standard battery and alternator
Tazer JL ( first model )
Firmware 11.06

At the beginning of each 7 day run a Deltran Battery Tender Plus was connected to JL until batteries were at 100%

First seven days Tazer JL was plugged in and married to JL then the below vehicle settings were changed and Tazer was removed but left married

Tire size
TPMS alarm limits
Fog light drop

Day 1
12.67 Main
12.67 N1
12.67 N2
12.6 EVIC

Day 2
12.63
12.63
12.63
13.0

Day 3
12.60
12.60
12.61
13.2

Day 4
12.60
12.59
12.59
13.2

Day 5
12.56
12.56
12.56
13.9
12.48 ( ESS battery added )

Day 6
12.66
12.66
12.66
13.3
12.64

Day 7
12.62
12.62
12.61
13.2
12.62

Averages
12.62 Main
12.62 N1
12.62 N2
13.1 EVIC
12.58 ESS

High Read-Low Read
12.67-12.56 Main
12.67-12.56 N1
12.67-12.56 N2
13.9-12.6 EVIC
12.64-12.48 ESS

Begin seven days with Tazer Jl plugged in, vehicle settings were left the same but live setting for ESS was set to disable ESS

Day 1
12.83 Main
12.83 N1
12.84 N2
12.7 EVIC
12.81 ESS

Day 2
12.66
12.67
12.67
13.0
12.67

Day 3
12.55
12.54
12.55
13.8
12.55

Day 4
12.55
12.57
12.58
13.4
12.58

Day 5
12.65
12.65
12.65
13.2
12.63

Day 6
12.58
12.59
12.59
13.0
12.60

Day 7
12.58
12.58
12.59
13.2
12.61

Averages
12.62 Main
12.63 N1
12.63 N2
13.1 EVIC
12.63 ESS

High Read-Low Read
12.83-12.55 Main
12.83-12.54 N1
12.84-12.55 N2
13.8-12.7 EVIC
12.81-12.55 ESS
 

wwood

New member
Thanks again guys, this ESS dual battery stuff is over my head and I appreciate the info. I was worried because I use deep cycle batteries to run my telescope equip and the smart chargers for deep cycle and normal auto start batteries do put out 14+ volts initially but then back off to lower voltages in stages to prevent over charging and finally just trickle charge to maintain full charge. I was surprised by the Jeep because the battery voltage gauge always runs in the low to mid 14s during normal driving but based on what you said I am just not running the Jeep long enough to get the batteries up to a true full charge - 12.7v. We mostly use the Jeep for daily driving, wife's shopping trips are short, maybe 10 min and my trips to the gun range only about a 30 minute run.
 

Wranglerman

New member
Thanks again guys, this ESS dual battery stuff is over my head and I appreciate the info. I was worried because I use deep cycle batteries to run my telescope equip and the smart chargers for deep cycle and normal auto start batteries do put out 14+ volts initially but then back off to lower voltages in stages to prevent over charging and finally just trickle charge to maintain full charge. I was surprised by the Jeep because the battery voltage gauge always runs in the low to mid 14s during normal driving but based on what you said I am just not running the Jeep long enough to get the batteries up to a true full charge - 12.7v. We mostly use the Jeep for daily driving, wife's shopping trips are short, maybe 10 min and my trips to the gun range only about a 30 minute run.

The easiest way to determine if you have any battery issues is to pull the ESS negative cable on the main battery negative post then use either a digital or analog meter to check the voltages, you have to pull the ESS negative to do that or you will be reading combined voltages from both.


You would put the positive meter lead on the positive post and then the negative lead on the negative post and this will be the main voltage and while keeping the positive lead on the positive post put the negative lead on the disconnected ESS negative cable and this will be the ESS battery voltage, also note if you have ESS disabled by pushing the button or having a programmer like a Tazer or Flashcal doing it for you it will say ESS off in screen #6 on the EVIC but after turning ESS on by pushing the button or removing the programmer and it says battery charging and does not let ESS engage I would venture to say you may have a battery issue, this is what mine did and after they replaced the main battery the running voltage dropped

Each battery needs to be in the 12.6-12.7 range
 

Cozdude

Guy with a Red 2-Door
14.5 is a very normal reading for a vehicle while running. Your charging system is powering the battery so all the electronics can run. While sitting 12.65 is a fully charged battery.
 

Wranglerman

New member
I have ridden in JL’s where the idle voltage is 12.7 and ramps up like mine does when slowing down or braking and I have also been in some where the voltage is 14.4 all the time and some are running programmers and some are not so it seems like it’s got a mind of its own but as stated as long as it starts and there are no error messages we should be good to go
 

NFRs2000NYC

Member
14.5 is a very normal reading for a vehicle while running. Your charging system is powering the battery so all the electronics can run. While sitting 12.65 is a fully charged battery.

I think some people were reporting that they have seen 12s and 13s while the Jeep is running. Maybe gecko can clarify, but it seems that the JL has electronics in between the alternator and batteries so it can disengage sort of, and not send a charge while the vehicle is running, allowing the running voltage to dip below the 14s....ie a smart alternator.
 

wwood

New member
Don't know if this means anything but we just drove the Jeep to the gun range for practice on the same road, same speed as always and the battery voltage gauge read 13.2v the whole way up and back???
It never did that before, always reading in the low to mid 14v range.
The only thing I did recently was re-seat all the fuses in the big fuse box next to the main battery. Read somewhere that these fuses are sometimes not fully seated from the factory so I pushed all of them in with my finger and about 6-7 of them did go in further and made a solid click.
Jeep drove same as always except that the voltage gauge read 13.2v.
Weird.
 

Cozdude

Guy with a Red 2-Door
I think some people were reporting that they have seen 12s and 13s while the Jeep is running. Maybe gecko can clarify, but it seems that the JL has electronics in between the alternator and batteries so it can disengage sort of, and not send a charge while the vehicle is running, allowing the running voltage to dip below the 14s....ie a smart alternator.

Anywhere between 13.2 and 14.8 is a normal operating range these days across all models and brands. The charging changes so quickly that the dash doesn’t keep up with it. It can go as low as being in the high 12’s and up to 15 at times. Proper range tho is 13.2-14.8
 

Wranglerman

New member
I think some people were reporting that they have seen 12s and 13s while the Jeep is running. Maybe gecko can clarify, but it seems that the JL has electronics in between the alternator and batteries so it can disengage sort of, and not send a charge while the vehicle is running, allowing the running voltage to dip below the 14s....ie a smart alternator.

This is what I was told and when the tech saw my battery tender quick disconnect he asked me about it and I told him that my JL sits sometimes days on end without running and I put it on a tender and he advised that doing this would keep my battery at peak charge, help the life of my battery and also keep the voltages low as the alternator does not have to work as hard sending voltage to the battery

As stated my main battery failed in about 7 months and who knows why it failed but was a pretty easy fix, I hate to think how big of a pain it’s going to be to change the ESS battery, I more than likely will bypass it when the day comes.
 

wwood

New member
The easiest way to determine if you have any battery issues is to pull the ESS negative cable on the main battery negative post then use either a digital or analog meter to check the voltages, you have to pull the ESS negative to do that or you will be reading combined voltages from both.


You would put the positive meter lead on the positive post and then the negative lead on the negative post and this will be the main voltage and while keeping the positive lead on the positive post put the negative lead on the disconnected ESS negative cable and this will be the ESS battery voltage, also note if you have ESS disabled by pushing the button or having a programmer like a Tazer or Flashcal doing it for you it will say ESS off in screen #6 on the EVIC but after turning ESS on by pushing the button or removing the programmer and it says battery charging and does not let ESS engage I would venture to say you may have a battery issue, this is what mine did and after they replaced the main battery the running voltage dropped

Each battery needs to be in the 12.6-12.7 range

Wrangler, thanks for the tip. I just performed your tests and all is well. With the engine off, the main battery reads 12.63v across the negative and positive posts and the ESS battery reads 12.65v when isolated by pulling the negative lead.
I do have a Taser with ESS Kill activated and I tested that by pushing the dash button to turn ESS on and it does work properly. No error messages about battery charging or anything else. So it looks like I am in good shape. Appreciate the help.
 

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