Starter battery issue

[Alomaofigaroll]

Hi,
Yesterday I had the top off and had parked up for a few hours. When I came back it wouldn’t start. Had a guy give me a jump then it started fine, came home left it over night. Started (nearly) the next morning but it was a sluggish start. Stopped it and waited a few minutes tried to start it again and wouldn’t.
Most likely battery.

Do I have to replace both battery’s or just the main one?

Sponsored

 

[Vinman]

Whatever you do don’t tell us what model/engine you have.

 

[Bill_P]

I would either replace both or just replace the main and delete the aux. When one dies it has a tendency to kill the other one. The Aux on my '18 went bad so I bought a new primary and deleted the aux by pulling a fuse and removing the aux negative battery cable and taping it off.

 

[Vinman]

Haha dare I ask why?

Does it have e-torque? Does it even have the 2nd battery?
First thing I would do is diagnose the issue before replacing the battery. Is there an excessive ignition off current drain?

 

[kah.mun.rah]

Have you tried starting it by pressing your fob against the ignition start button? Probably not the issue but worth a try.

 

[Vinman]

Gotcha.
It’s a 2018 3.6 Sahara.
I have noticed that the starter had been a little laboured a couple of times lately.
When I hit the start button it’s not ticking over just a feint click then nothing

I would start by charging the battery, then once the Jeep is running ensure the charging system is operating at the correct voltage. If it is then have thw battery load tested.
If the battery fails the load test, I would replace it along with the auxiliary battery or delete the smaller one all together.

 

[kah.mun.rah]

Gotcha.
It’s a 2018 3.6 Sahara.
I have noticed that the starter had been a little laboured a couple of times lately.
When I hit the start button it’s not ticking over just a feint click then nothing

The 3.6L in my 2018 went through aux batteries almost every 12 months. If you are still running on both original batteries I would replace them both.

 

[SparkleTooth]

Don't mess around with charging or any other shadetree tests. Do yourself a favor and replace both batteries. I am convinced that stock batteries are not strong enough right from the factory.
Get yourself a high quality H7 AGM battery and a matching aux battery if possible (I like DieHard).

 

[Fudster]

Ok so I charged the battery.
It started straight away.
I then did a battery load test.
However it’s results were “Weak”
So is it fair to say new battery needed?

It is not.

And this is the case unless you first electrically isolated your main and Aux batteries before effecting the load test.

I'm not saying your main and/or aux batteries aren't bad. I'm saying that if you did the load test with the batteries connected you did a composite load test of both batteries together from whose results limited information can be derived regarding the state of either individual battery.

Remove temporarily from the main battery's negative post the black cable that does NOT lead to the body ground on the passenger's side front quater panel.

After doing so put your load tester on the main battery's terminals and note your results. Next, move the negative side of the load tester to the dangling cable. That will be a load test of the Aux battery, yes, even though the positive side of the load tester is on the main battery's positive terminal.

 

[Vinman]

Ok so I charged the battery.
It started straight away.
I then did a battery load test.
However it’s results were “Weak”
So is it fair to say new battery needed?

Yes, I would replace the battery. And personally, I would delete the second smaller battery.
If a vehicle has a dual battery system it has always been said to ensure both batteries are the same age, size and capacity whenever possible.

I don’t understand why Jeep decided to pair a larger battery with a smaller battery in parallel. Old school thought is that is a recipe for battery failure and from the amount of posts with battery issues I tend to think the old school method of connecting multiple batteries together is still the correct way.

 

[TKL223/3]

It’s a lot easier taking the fender off to replace the aux battery.

 

[thestein13]

Ok done thanks everyone!
Bought a new Odyssey AGM H7 and auxiliary battery.
Replaced both this evening.
Getting at the Aux was a bitch but got there.
no more starting issues!

Is your aux battery an Odyssey?

Sponsored