Battery voltage observations

[Andy29847]

Mercy!!! These battery threads always go off in a lot of directions. Here are my thoughts:

When running the Jeep with 2 batteries, the dash voltmeter's primary value is to display that the alternator is working. The numbers displayed on the voltmeter do not reflect actual battery measurements because of the load of the Jeep systems. One thing that I have noticed is that charging voltage is always high when it is cold outside.

The 2 Jeep batteries have to be separated to make good tests. You can do this with the batteries still in the Jeep by disconnecting the aux battery negative cable. If you do it this way, be cautious with the loose end. If the loose end of the aux negative battery cable touches something, you might get a spark show or worse. You can test batteries with a voltmeter or with a load tester. My experience is that neither method works every time. In the case of our Jeeps, the ESS system acts as an early alarm for battery trouble. In a Jeep with a new battery, the ESS system activates in a mile or less after cranking. As the batteries get weak, it takes longer for the ESS to go active. ESS not working messages are a strong indicator that you have one (or 2) weak batteries. ESS not working with Mopar batteries that are 2-1/2 years old is your Jeep's desperate cry for new batteries. You read that right. Replace both batteries at the same time.

The IBS, AKA, intelligent battery sensor, is not smart. if it was smart, we wouldn't have a new thread about batteries every day.

I only have one battery in each of my Jeeps (Wrangler and Gladiator). I also use a Smart Stop/Start device to disable the ESS system. I think that the ESS should be disabled if you are only going to run with one battery. I haven't read where anyone has had damage from running one battery with ESS activated, but it seems like a low voltage condition could affect the Jeep systems. I err on the side of caution. I started a thread when I made this change.

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[J Sierra]

The voltage on the dash display comes from the IBS.

 

[Andy29847]

The voltage on the dash display comes from the IBS.

I think "through the IBS" is a more accurate statement. There are 2 voltage sources, the batteries and the alternator.

 

[Lost1wing]

Unplug the IBS. If the display shows approx 12vdc, that number is coming from the pdc or the bcm ( via lin bus). If it shows 0vdc, well then, maybe it does come from the IBS. What does the description and operation say? I have not looked.

 

[J Sierra]

The numbers displayed on the voltmeter do not reflect actual battery measurements

Not sure what your meaning is

 

[ShadowsPapa]

You can always swing into an auto parts or battery store and have it tested. Then you don't have to try and decipher what advice from an internet forum you trust.

Assuming the auto parts store has a decent tester (most don't) and have a person who wasn't flipping burgers last week (most don't)
We've seen them connect to the main battery, being totally clueless about these being a 2 battery parallel system.

Naw, avoid the parts stores - I've had nothing but bad luck and morons who don't know how to really test batteries in those places. I had a totally trash battery check as "ok" by one - even the expert battery sites admit too often those hand-held testers don't do a good job, plus, to really test, you need to charge a low battery before testing - those clowns will put that device on a battery reading 11 volts and try to test it. Clowns.

 

[J Sierra]

Battery Voltage Gauge - The BCM acquires the battery voltage directly from the battery by way of the Intelligent Battery Sensor (IBS). The BCM then sends this value in a signal on the CAN-C network to the IPC for the IPC display
This is from the service manual, but I just unplugged the IBS and the dash volt display is normal.
Also started normally and did not complain.

 

[ShadowsPapa]

The IBS, AKA, intelligent battery sensor, is not smart. if it was smart, we wouldn't have a new thread about batteries every day.

It's fine - it's the owners who usually get way off track not understanding how these work and try to apply "internet intelligence" (now there's a contradiction in terms, sort of like Senate intelligence committee is anything but)
The IBS is fine - however, over time, due to tolerances, it can drift. There's actually a fair amount of tolerance in those and after a couple of years, drift, as well as short drives, can lead to them being way off.
After my 2020 situation, and reading the real tech docs on these things, my plan is to do a full charge and IBS reset perhaps once a year, every two years, tops.
It's amazing what can throw these off.........

Here's some of the reasons they can be off - and gee, it includes a lot of what we see in these forums - short drives, batteries never being fully recharged.
I wonder why some of us have trouble, and some of us never do?

 

[Andy29847]

Not sure what your meaning is

The voltage reading is a reading from a circuit made up of the batteries, the alternator, and the electrical/electronic components.

 

[bluemoon110]

The dash battery gauge on my 2022 Max Tow Gladiator came on last week, reading 14.7 - 14.8. Most of my travel is around town as my daily driver, which is not much. Some day it sits. Upper SC winters are mild with occasional mid to low 20s temps. Should I be thinking about a new batter yet? The stop-start function stopped working some time back.

 

[Lost1wing]

The dash battery gauge on my 2022 Max Tow Gladiator came on last week, reading 14.7 - 14.8. Most of my travel is around town as my daily driver, which is not much. Some day it sits. Upper SC winters are mild with occasional mid to low 20s temps. Should I be thinking about a new batter yet? The stop-start function stopped working some time back.

I wouldn't be concerned too much. It wouldn't hurt to hook up a battery charger overnight. Don't wait for the dead or weak battery to show up.

 

[bluemoon110]

I wouldn't be concerned too much. It wouldn't hurt to hook up a battery charger overnight. Don't wait for the dead or weak battery to show up.

Thanks for the reply.

 

[CrazyCooter]

Nothing to see here.........Do some research on AGM battery charging profiles to see for yourself?

Also take into account your overnight temps combined with the draws these vehicles have and I see nothing wrong with 12.2V in the morning.

 

[J Sierra]

The IBS data

 

[Andy29847]

The IBS data

A whole lot of nothing. Thanks for sharing.

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