Voltage

[JTmac]

Trying to figure out if I messed something up. Truck wouldn’t start yesterday so took both batteries out and headed to autoparts store. Main tested as bad but went ahead and decided since I had it out to replace the aux as well. Truck is a 2020 and believe original owner began use in Nov 2019. Made the assumption if not bad yet it would be in near future.

When I got everything reassembled and started the truck I had several warning lights displayed including a check engine. Shut off and restarted, all lights went away except check engine. Drove around for a bit. Stopped and restarted. Still check engine light. Went to bed thinking I would get the code read next day. Read a bunch more forum stuff here and on JL forum and realized I probably didn’t disconnect everything the “right” way. (Have changed plenty of batteries in single battery systems before, but was probably over my head for this job. YouTube tends to make you feel like you can do anything ). I was initially following a YouTube video where the guy went from the top to get to aux battery. As I started removing the fuse box it would not come up, decided I would rather go thru wheel well than risk damaging something electrical.

Got in to head to parts store today to get the check engine code read. Code no longer displayed. Went anyway and they found it stored. The check engine code was for system voltage low.

Drove it around a bit after that. Voltage gauge when off reads 12.4. When running was 12.7 mostly but occasionally would fluctuate higher. My main question is is this normal voltage? It seemed like before changing the batteries, voltage was more around high 13’s to 14 when running. Do not recall what it was when off.

Read about risk of blowing your N3 if not careful when changing battery. My understanding is this would cause the alternator not to charge and the ESS to not work. The ESS is indicating it’s working. Display says Start/Stop Ready when driving. Not equipped to test the alternator etc. Wondering if I need a trip to dealer to get it checked out, or just continue to drive it and see if something happens. Thank you all in advance for any help!

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[sharpsicle]

Your voltage will only go up to 13-14v if it's actively charging the system. With a bad battery, it's going to be charging more often than with a new healthy one. It makes sense that you're seeing it in that range less often now. So there's nothing to worry about there. These alternators are not "100% on" like old-school ones used to be, they're controlled.

I don't see anything to be concerned about.

 

[JTmac]

That’s relieving. Thank you for the info and all the expertise you share on this forum!

 

[ShadowsPapa]

Did you fully charge each battery with a good charger BEFORE installing them?
Never install batteries from parts stores and then rely on the alternator to charge them.
A new battery may start the vehicle but unless the store charges them every week while on the shelves, they'll be seriously low.

If the batteries are fully 100% charged, you will run voltages in the upper 12s to lower 13s. Otherwise, should be in the 14s.
The voltage you see with it running will depend on the state of charge of the batteries and other factors.

Also when installing new batteries - besides charring each battery with a good charger before installation, pull the IBS and leave it disconnected for a few minutes (I shoot for 10 minutes) to reset it. Then it will learn with fully charged batteries. Otherwise your system won't know just what's going on, it won't know the true state of charge of those batteries and could be some issues.

Drove it around a bit after that. Voltage gauge when off reads 12.4. When running was 12.7 mostly but occasionally would fluctuate higher. My main question is is this normal voltage? It seemed like before changing the batteries, voltage was more around high 13’s to 14 when running. Do not recall what it was when off.

That's WAAY low and indicates your batteries are barely 50% charged. Running at 12.7 is also very low for batteries slapped in without charging them.
12.4 volts is low when sitting and indicates batteries not charged.
I'd frankly be concerned if all you see is 12.7 volts when driving it. Even after fully charging mine for a full day with a good charger, it will run in the 13s most of the time. The lower voltage is normally seen when there's a load on the engine, up hills and so on, or if the battery is hot and so on.

 

[JTmac]

Did you fully charge each battery with a good charger BEFORE installing them?
Never install batteries from parts stores and then rely on the alternator to charge them.
A new battery may start the vehicle but unless the store charges them every week while on the shelves, they'll be seriously low.

If the batteries are fully 100% charged, you will run voltages in the upper 12s to lower 13s. Otherwise, should be in the 14s.
The voltage you see with it running will depend on the state of charge of the batteries and other factors.

Also when installing new batteries - besides charring each battery with a good charger before installation, pull the IBS and leave it disconnected for a few minutes (I shoot for 10 minutes) to reset it. Then it will learn with fully charged batteries. Otherwise your system won't know just what's going on, it won't know the true state of charge of those batteries and could be some issues.



That's WAAY low and indicates your batteries are barely 50% charged. Running at 12.7 is also very low for batteries slapped in without charging them.
12.4 volts is low when sitting and indicates batteries not charged.
I'd frankly be concerned if all you see is 12.7 volts when driving it. Even after fully charging mine for a full day with a good charger, it will run in the 13s most of the time. The lower voltage is normally seen when there's a load on the engine, up hills and so on, or if the battery is hot and so on.

Thank you for that feedback. I did not charge them before installing. I wasn’t aware that was a thing. Is it possible to do so now that they are in the vehicle? Would rather not have to dig that aux battery out again. Can it be isolated and charged in place? If necessary I will do what I have to do. Any recommendations on a “good” charger.

 

[ScooterInTX]

Did you fully charge each battery with a good charger BEFORE installing them?
Never install batteries from parts stores and then rely on the alternator to charge them.
A new battery may start the vehicle but unless the store charges them every week while on the shelves, they'll be seriously low.

If the batteries are fully 100% charged, you will run voltages in the upper 12s to lower 13s. Otherwise, should be in the 14s.
The voltage you see with it running will depend on the state of charge of the batteries and other factors.

Also when installing new batteries - besides charring each battery with a good charger before installation, pull the IBS and leave it disconnected for a few minutes (I shoot for 10 minutes) to reset it. Then it will learn with fully charged batteries. Otherwise your system won't know just what's going on, it won't know the true state of charge of those batteries and could be some issues.



That's WAAY low and indicates your batteries are barely 50% charged. Running at 12.7 is also very low for batteries slapped in without charging them.
12.4 volts is low when sitting and indicates batteries not charged.
I'd frankly be concerned if all you see is 12.7 volts when driving it. Even after fully charging mine for a full day with a good charger, it will run in the 13s most of the time. The lower voltage is normally seen when there's a load on the engine, up hills and so on, or if the battery is hot and so on.

Now you have motivated me to check mine! Just installed my Blackvue which has a great parking feature. If the voltage gets to 11.8 while I'm parked, it will shut down to prevent completely draining the battery. It's been shutting down every night and I haven't thought about it at all since it's a brand new Jeep (5200 miles)!

Wonder if Jeep would replace the batteries if they are this new.

 

[sharpsicle]

Now you have motivated me to check mine! Just installed my Blackvue which has a great parking feature. If the voltage gets to 11.8 while I'm parked, it will shut down to prevent completely draining the battery. It's been shutting down every night and I haven't thought about it at all since it's a brand new Jeep (5200 miles)!

Wonder if Jeep would replace the batteries if they are this new.

Just to give you a reference, I run the BlackVue DR6502CH myself along with a hotspot for connectivity. Both go through the PMP. With that same 11.8v cutoff I can get 3 days out of them before the cutoff voltage is reached now that I've replaced the factory battery. With the original battery, it was maybe 24hrs at best.

 

[ScooterInTX]

Just to give you a reference, I run the BlackVue DR6502CH myself along with a hotspot for connectivity. Both go through the PMP. With that same 11.8v cutoff I can get 3 days out of them before the cutoff voltage is reached now that I've replaced the factory battery. With the original battery, it was maybe 24hrs at best.

Awesome! I have the same and just use my home WiFi when she's parked in the garage. So 24 hours would be typical? I only take short 15-30 minute trips and I was worried that wasn't enough to fully charge the battery or that I just got a dud from the factory.

 

[sharpsicle]

Awesome! I have the same and just use my home WiFi when she's parked in the garage. So 24 hours would be typical? I only take short 15-30 minute trips and I was worried that wasn't enough to fully charge the battery or that I just got a dud from the factory.

My battery was on its way out. So I wouldn't say 24hrs is typical, but more reflective of what my not-so-good battery was able to squeak out. And I'll say 24hrs might be a bit generous. The stock battery is trash and upgrading to something better immediately improved many things, such as my dashcam park time.

Also consider that the stock battery is going to degrade faster with the dashcam now, so putting something that handles that kind of cycle better would be a good thing to consider. I know there are mixed feelings on Optima batteries, but in my experience their yellow tops do a good job with this kind of stuff.

 

[ScooterInTX]

My battery was on its way out. So I wouldn't say 24hrs is typical, but more reflective of what my not-so-good battery was able to squeak out. And I'll say 24hrs might be a bit generous. The stock battery is trash and upgrading to something better immediately improved many things, such as my dashcam park time.

Also consider that the stock battery is going to degrade faster with the dashcam now, so putting something that handles that kind of cycle better would be a good thing to consider. I know there are mixed feelings on Optima batteries, but in my experience their yellow tops do a good job with this kind of stuff.

Makes sense. If you don't mind me asking, did you replace the aux battery at the same time? I always see threads on the this and how temperamental this setup is. Sounds like the best approach is to get a good aftermarket pair and have the dealership swap them out.

 

[sharpsicle]

Makes sense. If you don't mind me asking, did you replace the aux battery at the same time? I always see threads on the this and how temperamental this setup is. Sounds like the best approach is to get a good aftermarket pair and have the dealership swap them out.

I did just the main. My aux was fine. I totally accept that this may change in the near future, but for now it's not a problem for me. YMMV.

 

[jav_eee]

My jeep idles/drives at 14 volts all day every day. They checked my battery when I had my tires installed (Firestone complimentary service) and said it was good. You’ve just reminded me to check the voltage on it after it’s been sitting a while.

 

[HooliganActual]

Your voltage will only go up to 13-14v if it's actively charging the system. With a bad battery, it's going to be charging more often than with a new healthy one. It makes sense that you're seeing it in that range less often now. So there's nothing to worry about there. These alternators are not "100% on" like old-school ones used to be, they're controlled.

I don't see anything to be concerned about.

That’s relieving. Thank you for the info and all the expertise you share on this forum!

Sharpsicle (and others since his post) are right. I can't say "all Gladiators", because I don't have supporting data, but MY Gladiator has what they refer to as a "Smart Alternator" and to Sharp's point, they are not running at the higher voltages all the time. For an old timer like me, that did take a bit of getting used to.

Also, I have had to disconnect my battery several times for various reasons and it seems like I always get that CEL light that hangs around for a few hours before it clears...so no need to stress out if it doesn't clear immediately. As I was doing some electrical work on my Gladiator one day, I had it clear 5 minutes after it started, an hour after it started and another time by the next morning like your scenario. Jeep brains have brain worms I think.

My jeep idles/drives at 14 volts all day every day. They checked my battery when I had my tires installed (Firestone complimentary service) and said it was good. You’ve just reminded me to check the voltage on it after it’s been sitting a while.

I think I'd go have that checked out by a Jeep Service center (not Firestone). It shouldn't be always up at 14V.

 

[jav_eee]

I think I'd go have that checked out by a Jeep Service center (not Firestone). It shouldn't be always up at 14V.

yeah I don’t trust any of them. Not Firestone, not Jeep, none of them. I’m not too worried about it, it’ll be interesting to see how long it lasts in this supposedly weakened state.

 

[HooliganActual]

yeah I don’t trust any of them. Not Firestone, not Jeep, none of them. I’m not too worried about it, it’ll be interesting to see how long it lasts in this supposedly weakened state.

I guess I'd be worried that if the alternator is constantly running at that higher state, there's a chance that it could damage the battery or it may indicate that it is in some failure mode already. I lost an alternator in my CJ driving down the highway and it only took about 15 minutes of firing the engine at highway speeds to drain the battery.

Theoretically, it costs you nothing to have the dealer check it out as you're probably still under warranty. I'd rather have them pay for replacing the alternator if there is actually a problem.

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