Voltage too low?

[Terminus33]

Hey guys I know something's probably wrong with my Gladiator and I'm hoping it's just the batteries.
I just had an ESS event and when it started all the lights dimmed down pretty low like the battery is about to die.. So I checked my voltages while driving home the highest I ever get is 14 V in neutral coasting the other picture is while driving. I'm probably going to replace both batteries do you think that'll fix the issue?

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[ShadowsPapa]

No that's not too low. These are smart systems. Mine ran as low as 12.7 volts last summer on a long trip. It's not the most frequent thing but it's not out of the ordinary either.
These are no longer constantly regulated systems where it's always charging at a specific range such as 13.8-14.2 those are old school voltages.
But you should also see voltages up in the 14-14.6 range as well.
So while 12.8 isn't "too low" - they will get down that low at times - you have something going on.

 

[Fouts]

No that's not too low. These are smart systems. Mine ran as low as 12.7 volts last summer on a long trip. It's not the most frequent thing but it's not out of the ordinary either.
These are no longer constantly regulated systems where it's always charging at a specific range such as 13.8-14.2 those are old school voltages.
But you should also see voltages up in the 14-14.6 range as well.
So while 12.8 isn't "too low" - they will get down that low at times - you have something going on.

HUH?

 

[ShadowsPapa]

HUH?

What do you mean "huh?" - that's a fact that these can see voltages in the upper 12s. It's been talked about here, there's Jeep communications about it and I've seen it personally.
There's no more "regulated at xx.xx volts" systems out there.
There's no saying he's not got an issue because of OTHER symptoms, the lights dimming and battery issues indicate that he's got something going on, but the 12.8 volts alone is not the issue.
An operating voltage in the 12s is normal and when all else is fine, nothing to worry about.
I've done auto-electric for decades.
If the IBS detects an acceptable SoC they go into trickle charge mode - 12.7-low 13s to prevent heating the batteries and reduce needless load on the system.
Under heavy acceleration they shut down charging and you could see voltages as low as 12.2-12.4

This picture is from my own truck this last summer. AC was on, cruise was on, everything was working just fine.

And this is what Jeep says about it -

 

[Terminus33]

I do understand the low voltage is ok because if the "inverter" alternator but after that pic on the way home I got down to 12.5v constant while driving and it never goes above 14v ever. I used to have the jeep shut off in ESS at almost all lights, not I get lucky if it happens twice a day. I drive about 300 miles a day.

 

[ShadowsPapa]

I do understand the low voltage is ok because if the "inverter" alternator but after that pic on the way home I got down to 12.5v constant while driving and it never goes above 14v ever. I used to have the jeep shut off in ESS at almost all lights, not I get lucky if it happens twice a day. I drive about 300 miles a day.

Yeah, yours is definitely ill - needs a doctor.
IBS problem? It's not sensing the low battery charge perhaps?
Bad batteries also may not represent a "load" to the charging system and present a false indication.
While the occasional 12.x volts is normal, yours is sick.

 

[Terminus33]

Yeah, yours is definitely ill - needs a doctor.
IBS problem? It's not sensing the low battery charge perhaps?
Bad batteries also may not represent a "load" to the charging system and present a false indication.
While the occasional 12.x volts is normal, yours is sick.

That's my fear, Jeep makes diagnosing these things so difficult that the average home mechanic has no means to figure out if we should just replace the battery or alternator. Instead we have to take it to a specialist and pay a premium for something that seems like just an easy dead battery swap.

It has been about 50k miles in Florida heat with over a year. Batteries tend to go out quick here.

 

[Mr._Bill]

Hey guys I know something's probably wrong with my Gladiator and I'm hoping it's just the batteries.
I just had an ESS event and when it started all the lights dimmed down pretty low like the battery is about to die.. So I checked my voltages while driving home the highest I ever get is 14 V in neutral coasting the other picture is while driving. I'm probably going to replace both batteries do you think that'll fix the issue?

How old are the batteries? What is the voltage reading from each with the truck off? Disconnect each battery and load test them. If they are not healthy, replace them. If they are good, have the intelligent battery sensor checked or replaced.

I still have the original batteries in my truck. They are almost three years old. The sitting voltage is 12.3 just after turning it off. I drove 10 hours yesterday, with the voltage level showing around 14.3 for the entire trip. After getting back and parking this morning, it was showing a resting voltage of 12.0 with an outside temperature of 39 degrees.

I don't use ESS very often. I've never had an issue with lights dimming, but also have the factory installed LED lights.

 

[ShadowsPapa]

How old are the batteries? What is the voltage reading from each with the truck off? Disconnect each battery and load test them. If they are not healthy, replace them. If they are good, have the intelligent battery sensor checked or replaced.

I still have the original batteries in my truck. They are almost three years old. The sitting voltage is 12.3 just after turning it off. I drove 10 hours yesterday, with the voltage level showing around 14.3 for the entire trip. After getting back and parking this morning, it was showing a resting voltage of 12.0 with an outside temperature of 39 degrees.

I don't use ESS very often. I've never had an issue with lights dimming, but also have the factory installed LED lights.

Wow, that's low.
Even AGM batteries should be well over 12 when charged - more like 12.6 or so.
12.3 after charging would normally indicate it's old and not taking a full charge. Surface charge should be 12.8-13.0

This is from a battery source -
A 12-volt AGM battery typically reads 12.7V to 13.0V when full and unloaded

 

[Terminus33]

How old are the batteries? What is the voltage reading from each with the truck off? Disconnect each battery and load test them. If they are not healthy, replace them. If they are good, have the intelligent battery sensor checked or replaced.

I still have the original batteries in my truck. They are almost three years old. The sitting voltage is 12.3 just after turning it off. I drove 10 hours yesterday, with the voltage level showing around 14.3 for the entire trip. After getting back and parking this morning, it was showing a resting voltage of 12.0 with an outside temperature of 39 degrees.

I don't use ESS very often. I've never had an issue with lights dimming, but also have the factory installed LED lights.

All I have is a MultiMeter, not sure I can properly load test a battery with it but I can get a voltage reading. The batteries are factory Jeep on my 2020.

Wow, that's low.
Even AGM batteries should be well over 12 when charged - more like 12.6 or so.
12.3 after charging would normally indicate it's old and not taking a full charge. Surface charge should be 12.8-13.0

This is from a battery source -
A 12-volt AGM battery typically reads 12.7V to 13.0V when full and unloaded

That's what I thought as well, always seemed like a good battery should never get close to 12.0v. when mine hit 12.5v I knew something was up.

 

[ShadowsPapa]

The GM chart I have shows that a battery voltage of 12.45 is 75% charged.
Granted it's an older chart, but..........

AGM is a bit different but pretty close - most say 12.0 is 50% charge.
Looks like AGM is similar - 80% at 12.5 so it's really not that different than my chart.

 

[Fouts]

https://www.jlwranglerforums.com/forum/threads/low-voltage-on-the-3-6.23751/

 

[ShadowsPapa]

https://www.jlwranglerforums.com/forum/threads/low-voltage-on-the-3-6.23751/

Looks like they were alarmed and guessing as well..............
The information is out there, there are publications, and yet - it's a lot of "I think" or "maybe it's...."

Terminus33 has an issue with his - but the low voltage by itself isn't reason for alarm.
Combined with OTHER symptoms, he needs to have it checked.
But anyone seeing voltage in the mid-12s and NO other problems or symptoms should step forward out of the 1980s.
And if they see even lower voltages - like 12.4 or so, when under heavy acceleration, but it then pops back up a bit - it's how they get power for the acceleration. Alternators take HP to generate power. It ain't a free lunch. It's a clever way of taking back a couple HP or so.
My alternator test stand has a multi-HP electric motor and a large alternator can make it work when I really crank that carbon pile or full-field the thing.

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