Battery voltage observations

[Maverickxeo]

On my 23 Overland 3.6L, I've been very mindful of my battery voltage lately.

I've been driving it daily, typically at least 60KM a day on the highway. It has been getting colder, (-10C) but I've noticed that my voltage, while driving, is ALWAYS at 14.5V to 14.9V.

While parked, I have been seeing it down to 12.2V overnight.

I don't have any real "symptoms" of a weak battery, but I'm wondering if the batteries are starting to fail - I can't imagine how I can be running at 14.9V for over 60KM (per day) and still not having a battery fully charged.

Is the dash "gauge" just a dummy light to prevent people from reporting concerns due to dropping voltage, or does it actually show true voltage being run from the alternator?

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[Lost1wing]

I would suggest separating the grounds at the main negative battery and charging both batteries separately. After charging each, measure the voltage of each one. Hope for 12.6 or better. That alone does not mean your batteries are good but it's a start. While you are charging your batteries, disconnect the ibs connector and plug it back in after you reconnect the batteries.

The higher voltage readings are telling you that your batteries are in a discharged state or your IBS needs to be reset. The IBS can not see the charger if you connect the charger at the post and not at the top plate.

I would guess that your ESS page says battery charging or not ready.

 

[Maverickxeo]

I would suggest separating the grounds at the main negative battery and charging both batteries separately. After charging each, measure the voltage of each one. Hope for 12.6 or better. That alone does not mean your batteries are good but it's a start. While you are charging your batteries, disconnect the ibs connector and plug it back in after you reconnect the batteries.

The higher voltage readings are telling you that your batteries are in a discharged state or your IBS needs to be reset. The IBS can not see the charger if you connect the charger at the post and not at the top plate.

I would guess that your ESS page says battery charging or not ready.

ESS is still working - which is even more confusing.

Does the IBS need to be reset at times? Do I just disconnect the negative terminal on the main battery to do so?

 

[Flanders]

12.2V is low. EOL low.

A few hundred hours of float charge at 13.5-13.8V might improve things but

The popular smart chargers don't even have a proper float voltage. Some of them have a maintenance voltage around 13.2V, which would do some good but will never achieve a full charge.

 

[GeekJT]

On my 23 Overland 3.6L, I've been very mindful of my battery voltage lately.

I've been driving it daily, typically at least 60KM a day on the highway. It has been getting colder, (-10C) but I've noticed that my voltage, while driving, is ALWAYS at 14.5V to 14.9V.

While parked, I have been seeing it down to 12.2V overnight.

I don't have any real "symptoms" of a weak battery, but I'm wondering if the batteries are starting to fail - I can't imagine how I can be running at 14.9V for over 60KM (per day) and still not having a battery fully charged.

Is the dash "gauge" just a dummy light to prevent people from reporting concerns due to dropping voltage, or does it actually show true voltage being run from the alternator?

These newer alternators voltage control is pretty good I've noticed, If your running heat with decent blower speed, heated seats, heated steering in -10c I would not be surprised to see the alternator putting out 14.8v nominal is ok. 14.9v is easily within spec.

12.2 volts at rest at -10c is pretty normal. (bout 60% charge) Cold battery loses a little capacity. About 12.6v is normal resting voltage at like 25c. The alternator putting out 14.8 - 14.9v is pretty normal in very cold temps.

Battery age could be a factor if it's more than 2 years old, in cold temps, could be worth swapping, but if it's not losing voltage lower than say 12.0v, should be fine. If it's not hard to start, etc. Wouldn't worry about it until you're seeing like 11.8v at rest, then maybe you are starting to lose a cell or a cell is getting weak, but 12.2 at rest wouldn't bother me at all in cold. Heck I think mine is about 12.4-5 now at 5c and it's brand new.

 

[Maverickxeo]

These newer alternators voltage control is pretty good I've noticed, If your running heat with decent blower speed, heated seats, heated steering in -10c I would not be surprised to see the alternator putting out 14.8v nominal is ok. 14.9v is easily within spec.

12.2 volts at rest at -10c is pretty normal. (bout 60% charge) Cold battery loses a little capacity. About 12.6v is normal resting voltage at like 25c. The alternator putting out 14.8 - 14.9v is pretty normal in very cold temps.

Battery age could be a factor if it's more than 2 years old, in cold temps, could be worth swapping, but if it's not losing voltage lower than say 12.0v, should be fine. If it's not hard to start, etc. Wouldn't worry about it until you're seeing like 11.8v at rest, then maybe you are starting to lose a cell or a cell is getting weak, but 12.2 at rest wouldn't bother me at all in cold. Heck I think mine is about 12.4-5 now at 5c and it's brand new.

That is all great to hear!

I've never actually bothered checking the actual voltage until this year - figured I should be watching it as it approaches 3-4 years old.

For what it's worth - I have a 4.0L TJ that sits for a literal month and it still fires up without any sort of charger.

 

[ShadowsPapa]

While parked, I have been seeing it down to 12.2V overnight.

If you are reading that from the dash - don't. That's with the load of the electronics powered up.

Let the truck sit for hours, keep the fob well away from it and then open the hood and use a real volt meter on the battery terminals to get a voltage reading.
You can't use the cluster number to get a good idea of the battery voltage when it's off because it's loading the batteries while you read it.

Wouldn't worry about it until you're seeing like 11.8v at rest, then maybe you are starting to lose a cell or a cell is getting weak, but 12.2 at rest wouldn't bother me at all in cold. Heck I think mine is about 12.4-5 now at 5c and it's brand new.

Wow, that's totally dead at that number. And even yours isn't good at all with those numbers.
If mine get down to 12.4 - which is around half-charged, I'd be thinking about a GOOD maintainer on it, charging it up.
Of course reading the number from the dash is never a good idea - you don't know what's really happening as all of the modules are awake and loading the batteries.
11.8 is DEAD and is likely to cause PCM resets or even lack of starting, possibly leaving him stranded - it's a discharged and bad battery situation, sorry, not great advice
I'd be freaking if mine got under 12.2 as that means it's well under 50% charge - and batteries that sit at those low numbers go bad because of sitting discharged.
11.8 is bad battery territory and no one should ever let theirs get even under 12.4 for any length of time. It will ruin them

 

[Maverickxeo]

If you are reading that from the dash - don't. That's with the load of the electronics powered up.

Let the truck sit for hours, keep the fob well away from it and then open the hood and use a real volt meter on the battery terminals to get a voltage reading.
You can't use the cluster number to get a good idea of the battery voltage when it's off because it's loading the batteries while you read it.

I'm reading it from the battery using a voltmeter with it not running the next morning.

 

[JeepOfTheseus]

11.8 is bad battery territory and no one should ever let theirs get even under 12.4 for any length of time. It will ruin them

 

[The Sigma]

https://www.jeepgladiatorforum.com/forum/threads/my-thoughts-on-the-auxiliary-battery.75273/

 

[JTdiRtyD]

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.

 

[Lost1wing]

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.

Some autopart stores will not touch dual battery set-ups. He would have to remove the batteries for them to test them.

 

[Lost1wing]

ESS is still working - which is even more confusing.

Does the IBS need to be reset at times? Do I just disconnect the negative terminal on the main battery to do so?

You should not need to reset the IBS. If you need a jump start or have had a dead battery, you could benefit by doing an IBS reset. Only do it after independently charging both batteries and verifying they can hold a charge. Disconnecting the connector at the IBS sensor will reset it. I would unplug it while the batteries are charging and reinstall the connector as my last step.

 

[Squashead]

I've been driving it daily, typically at least 60KM a day on the highway. It has been getting colder, (-10C) but I've noticed that my voltage, while driving, is ALWAYS at 14.5V to 14.9V.
due to dropping voltage, or does it actually show true voltage being run from the alternator?

Mine has been in that exact range since day one (2.5 years now). I have never checked the battery voltage since it was from day one, but I will now. I did think it was strange when we got a Grand Cherokee for my wife and the running voltage is more like 13-13.4 but I chocked it up to my max tow alternator putting out more power.

 

[Lost1wing]

My build date is 11/19. I didn't purchase it until 12/20. I had less than 100 miles on it when I bought it. It did a lot sitting around, so it is possible that the original batteries have been replaced before I bought it. I can still say that my batteries are over 5 years old. All that to say, my voltages while driving are 14.2 most of the time now that the heated steering wheel and heated seats are on. ESS says Not Ready battery charging. I still see 12.6 volts before starting.

The plan is to replace the batteries after I have the corrosion warranty work completed. The dealer will have it for a week and I wouldn't trust them to not kill the new batteries in that time.

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