Bass hits, voltage 14.6 to 13.2?

[jeeper2269 10+ year member]

I have a 2021 Jeep Wrangler Unlimited that has two batteries. One main and an auxiliary for the start stop function.

recently the lights were left on and the battery/batteries drained completely. We were able to charge andthen get her running again. However, the dash has an error, indicating the auxiliary battery is toast. It still starts and runs fine. I am replacing the auxiliary battery soon.

I did notice the headlights (led) dim a tiny bit when the bass hits and the voltage goes from 14.6 to 13.2.

this is the factory battery.

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[Popwarhomie 5,000+ posts]

Is there a question here?

 

[jeeper2269 10+ year member]

Is there a question here?

Hit the send button too fast.
Is this normal?

is it going to wear out the main battery quicker?

I’m assuming a big three upgrade will help regardless.

 

[SlugButter]

I would replace the auxiliary battery. That would be the battery for accessories, like a stereo. It’s probably a deep cycle type battery. You’re probably ok running just the one battery with the engine running but it will probably help dimming to have your aux battery and the big 3.

 

[SlugButter]

And it will likely wear out your front battery faster unless you put a big beefy battery up front.

 

[jeeper2269 10+ year member]

I would replace the auxiliary battery. That would be the battery for accessories, like a stereo. It’s probably a deep cycle type battery. You’re probably ok running just the one battery with the engine running but it will probably help dimming to have your aux battery and the big 3.

It’s one of those little guys. Another Jeep guy got the diehard platinum agm from advanced auto and suggested it. I actually disabled the start stop function, so I am not concerned about that. I just want to prevent future issues.
What kind of “beefy” battery is recommended for the Larger one ?

 

[SlugButter]

It’s one of those little guys. Another Jeep guy got the diehard platinum agm from advanced auto and suggested it. I actually disabled the start stop function, so I am not concerned about that. I just want to prevent future issues.
What kind of “beefy” battery is recommended for the Larger one ?

I’m not sure on your Jeep which specific battery fits your tray and has positive and negative on the correct side, but a good AGM battery would by my choice.

 

[SlugButter]

Largest AGM you can fit or afford.

 

[Buck 5,000+ posts]

Have you tried charging the dead battery? You should pull the battery out and check it's resting voltage after letting it sit for a while. Just because you heavily drain a battery doesn't mean it's dead. An alternator won't deep charge a battery like an actual battery charger will. Alts are more designed to power the vehicle when the vehicle is on that actually charge dead batteries. They help recharge batteries, but there's a certain level of drain where they just need to be charged.

That's the first thing I would do is simply take the bad battery out, test the voltage, and see if the battery is actually bad or just drained low. A dead cell in a 12v battery may make you read 9v or so, so look for some voltage reading like that.

 

[jeeper2269 10+ year member]

Have you tried charging the dead battery? You should pull the battery out and check it's resting voltage after letting it sit for a while. Just because you heavily drain a battery doesn't mean it's dead. An alternator won't deep charge a battery like an actual battery charger will. Alts are more designed to power the vehicle when the vehicle is on that actually charge dead batteries. They help recharge batteries, but there's a certain level of drain where they just need to be charged.

That's the first thing I would do is simply take the bad battery out, test the voltage, and see if the battery is actually bad or just drained low. A dead cell in a 12v battery may make you read 9v or so, so look for some voltage reading like that.

it’s an interesting setup with the small auxiliary battery under the main one. I tried charging both batteries separate and was only able to get the larger one to charge. That said, I didn’t pull the small one out, because it’s a pain to do. I will see if advanced auto parts can test the voltage on each when I go down there. The auxiliary battery I was looking at is only $109.

 

[hispls 5,000+ posts]

You have not told us how much power you're attempting to run for amps.

For what it's worth, flooded type batteries get damaged very quickly from deep cycling (complete discharge). From my experience once you do that about 3 times they're completely hosed. If you're concerned the way to test them is to uninstall and take them down to a parts store and have them "load tested". Just pulling a resting voltage off a battery will normally show you if one is completely dead but will not reveal one that's only functioning at 20% or so.

That auxiliary battery group 401 looks like the size I run in my 4 wheeler so I wouldn't expect that's doing a lot of heavy lifting for you. Even filling that size spot with lithium wouldn't give you a whole lot of extra storage or current on demand. IMO that seems a very silly design, but then again those cars that start and stop the engine all the time when you're stopped at a light or whatever feel like a recipe for trouble down the road in the first place.

In general voltage dipping down into the low 13s isn't going to hurt your amps or vehicle electronics but you're certainly working your alternator and batteries harder than if you didn't have any accessories so if you're getting into this sort of thing you should expect to replace alt/batteries more frequently than you would be if you were just keeping everything stock.

 

[LsGuy]

It's not normal, and usually indicates the aux battery failing (widely known issue on these jeeps). But, since your aux battery is fried, you already know what's causing it. The main battery is an agm from the factory, and I believe the aux is as well. Take it to the dealership, they usually replace the aux battery no questions. You have a 200-240 amp alternator (depending on options), a seperate motor generator, and 2 batteries. Unless you are running a super stout system, voltage drop won't be an issue, and big 3 probably isn't necessary. If you do decide to do big 3, research it since the wiring in these jeeps is more complex than standard battery alt setups. As a reference, I'm running 2k rms in my 21 jlu and the electrical system doesn't even notice it's there. Never any voltage drop at all.

 

[jeeper2269 10+ year member]

It's not normal, and usually indicates the aux battery failing (widely known issue on these jeeps). But, since your aux battery is fried, you already know what's causing it. The main battery is an agm from the factory, and I believe the aux is as well. Take it to the dealership, they usually replace the aux battery no questions. You have a 200-240 amp alternator (depending on options), a seperate motor generator, and 2 batteries. Unless you are running a super stout system, voltage drop won't be an issue, and big 3 probably isn't necessary. If you do decide to do big 3, research it since the wiring in these jeeps is more complex than standard battery alt setups. As a reference, I'm running 2k rms in my 21 jlu and the electrical system doesn't even notice it's there. Never any voltage drop at all.

well, I am running a teramps 3500 watts to my FI q 12 and the us acoustics barabara ann to four Polk audio db652s. 700 watts. I have the Tazer Mini, so I am able to permanently turn the start stop function off. However, I have the stupid light and “service start stop” on the display. Since I have the voltage drop, and the error, i was told the auxiliary battery is done (and “garbage” anyway) It also sounds like having the auxiliary battery dead can/will cause me issues down the road.
Thanks for all the replies. I figured the voltage drop was not normal and a sign. I’m probably just going to go down and get diehard platinum agm replacements for both today. $209 + $109 = $318 total to not have to worry about it for a while.

i would take it to the stealership, but it’s thirty miles away and they would just replace it with crap and/or charge me for it. Yeah, not a fan

note* I don’t have the upgraded aux or tow package

 

[sizmtrz]

Forgive my Ignorance, what is the “big 3”? Thank you.
Size

 

[LsGuy]

well, I am running a teramps 3500 watts to my FI q 12 and the us acoustics barabara ann to four Polk audio db652s. 700 watts. I have the Tazer Mini, so I am able to permanently turn the start stop function off. However, I have the stupid light and “service start stop” on the display. Since I have the voltage drop, and the error, i was told the auxiliary battery is done (and “garbage” anyway) It also sounds like having the auxiliary battery dead can/will cause me issues down the road.
Thanks for all the replies. I figured the voltage drop was not normal and a sign. I’m probably just going to go down and get diehard platinum agm replacements for both today. $209 + $109 = $318 total to not have to worry about it for a while.

i would take it to the stealership, but it’s thirty miles away and they would just replace it with crap and/or charge me for it. Yeah, not a fan

note* I don’t have the upgraded aux or tow package

Solid plan, you may actually be pushing the stock electrical system with that much power on the smaller alternator. I also have the tazer mini, one of the greatest tools ever made, but I don't have any lights or service Start stop on my dash, so that's a bit strange

Forgive my Ignorance, what is the “big 3”? Thank you.
Size

https://www.caraudio.com/threads/official-caraudio-com-big-3-thread.150087/