Aux Battery Replacement - both?

[WiseguyDS]

I'm currently tracking down an ESS/battery issue and will be replacing the AUX battery. My son suggested replacing both batteries or I would shorten the lifespan of the main battery. If the main battery checks out, is there consensus here on always replacing both batteries when one goes bad?

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[CarbonSteel]

In my experience, it can depend. When my first auxiliary battery failed, they were both nearing 3 years old so I replaced both of them.

A year later, it failed again and I only replaced the auxiliary as the main tested just fine.

If they are older, I would replace both. Be very careful not to short any wiring as the N3 fuse can blow and cause weird things to happen.

 

[WiseguyDS]

In my experience, it can depend. When my first auxiliary battery failed, they were both nearing 3 years old so I replaced both of them.

A year later, it failed again and I only replaced the auxiliary as the main tested just fine.

If they are older, I would replace both. Be very careful not to short any wiring as the N3 fuse can blow and cause weird things to happen.

Interesting and maybe a coincidence... mine are nearing 3 years old.

 

[58Willys]

Interesting and maybe a coincidence... mine are nearing 3 years old.

If they’re three years old, definitely replace both.

 

[The Last Cowboy]

I replaced both at 3 years old. The aux died first, for about a year I had no ESS. Then about a year later the main died. I replaced them both at the same time and all is well. I went with a larger H7 for the main though, and if/when (more like when) the aux dies again, it will be deleted.

I would suggest replacing the main with a 94R H7, then deleting the aux altogether. If you drive in town/short trips a lot, you might want to use a Tazer to disable ESS, if not, the H7 should be enough to handle everything. If you have a lot of electrical accessories you may also want to consider disabling ESS if you delete the aux.

 

[WiseguyDS]

I replaced both at 3 years old. The aux died first, for about a year I had no ESS. Then about a year later the main died. I replaced them both at the same time and all is well. I went with a larger H7 for the main though, and if/when (more like when) the aux dies again, it will be deleted.

I would suggest replacing the main with a 94R H7, then deleting the aux altogether. If you drive in town/short trips a lot, you might want to use a Tazer to disable ESS, if not, the H7 should be enough to handle everything. If you have a lot of electrical accessories you may also want to consider disabling ESS if you delete the aux.

Did you research? What battery brand did you select? Thanks!

 

[The Last Cowboy]

Yes, I researched. The batteries I bought are from O'Reilly's, Super Start. They are made by East Penn/Deka. I've had excellent results with that brand in the past. Napa's batteries are made by the same company. Other great battery brands are Northstar and Odyssey.

The reason I chose the Super Start is that I could go buy them that day, and I f I ever have a problem, the store is about 5 miles away. If Napa was closer, I would have used them. I didn't want to have to order a battery online, then have to deal with customer service over the phone and shipping it back if I had a problem.

 

[Jammer]

I thought about replacing and putting two big batteries. I've seen people do it but I've had shops tell me it will mess it up It's not made to run with two big batteries. You need the auxiliary battery still hooked up the way they've got it connected from the factory. What y'all's opinion on that?

 

[WiseguyDS]

Update: I bought the Smart Stop Start device by TheJagWrangler for $130. Granted I had to enlist the wife to help reach the cable harness located about 6" above the diagnostic port. My fat hands were too big to reach all the way in there and even she had a tough time but was a good sport about it. I owe her dinner.

The SmartStopStart module worked right off. It reads the last known state of the ESS and simply sets it to that state the next time the jeep is started. I'm posting the photo in the instruction set on where it plugs in. It's a great solution.

 

[jaymz]

I thought about replacing and putting two big batteries. I've seen people do it but I've had shops tell me it will mess it up It's not made to run with two big batteries. You need the auxiliary battery still hooked up the way they've got it connected from the factory. What y'all's opinion on that?

Find another shop. They're wrong.

The "big" and "little" batteries are essentially two glasses of water connected together. The big one will always try to fill the little one to the same level, thus draining the big one. Two of the same size eliminates the problem.

 

[multicam]

I thought about replacing and putting two big batteries. I've seen people do it but I've had shops tell me it will mess it up It's not made to run with two big batteries. You need the auxiliary battery still hooked up the way they've got it connected from the factory. What y'all's opinion on that?

Yeah, they’re definitely wrong about that and to your last point- you absolutely do not need both batteries hooked up. I “deleted” my aux battery ages ago by pulling the #42 fuse and disconnecting the aux battery negative terminal. No ill effects whatsoever.

 

[Rhinebeck01]

Update: I bought the Smart Stop Start device by TheJagWrangler for $130. Granted I had to enlist the wife to help reach the cable harness located about 6" above the diagnostic port. My fat hands were too big to reach all the way in there and even she had a tough time but was a good sport about it. I owe her dinner.

The SmartStopStart module worked right off. It reads the last known state of the ESS and simply sets it to that state the next time the jeep is started. I'm posting the photo in the instruction set on where it plugs in. It's a great solution.

Here is a better pic of where the @SmartStopStart unit plugs into..

 

[Jammer]

Find another shop. They're wrong.

The "big" and "little" batteries are essentially two glasses of water connected together. The big one will always try to fill the little one to the same level, thus draining the big one. Two of the same size eliminates the problem.

So the little battery does accessories and the start stop which I have turned off with my tazer. If you have two big batteries does one of them do the accessories and start stop if you have to take the tazer out when he takes to the dealer to get worked on for warranty work ? And I looked at that kid I think the kid was like five or $600 then the battery and labor It's quite a bit of labor I was told They wanted to charge me like $1,200 with the battery but I guess you need to get the same batteries alike like two Odyssey batteries and so be more You don't want two different batteries I guess be nice to have the exact same battery or you probably need the exact same batteries I can never do that I have to pay somebody to hook it all up though So you have it now?

 

[jaymz]

So the little battery does accessories and the start stop which I have turned off with my tazer. If you have two big batteries does one of them do the accessories and start stop if you have to take the tazer out when he takes to the dealer to get worked on for warranty work ? And I looked at that kid I think the kid was like five or $600 then the battery and labor It's quite a bit of labor I was told They wanted to charge me like $1,200 with the battery but I guess you need to get the same batteries alike like two Odyssey batteries and so be more You don't want two different batteries I guess be nice to have the exact same battery or you probably need the exact same batteries I can never do that I have to pay somebody to hook it all up though So you have it now?

I have no personal experience with the dual battery kits, so I can’t speak to that. I also have not experienced anything negative with the factory system. It works fine for me. I do know that mixing batteries of different capacities is not a good idea for the reasons mentioned previously.

That being said, I think that the dual battery kits that are available are a huge waste of money for most people. If I ever experience an issue with the OEM dual battery setup I will most likely just eliminate the small auxiliary battery altogether. I can’t imagine that it’s even necessary to be there in the first place as it seems that it creates more issues than it solves.

 

[Jammer]

One time my jeep would not shut off even when i discounted both cables on the big battery. they said because the little axu battery was going bad so it wont turn off the motor. finally it shut off and had to buy both batterys, again 2 yrs later it happened again. so if i discount the neg cable and fuse 42 i juust run everything off the one big battery thats al and no probles ?

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