testing each battery separately?

[rickinAZ]

I'm taking my JL to Autozone to test the batteries. Is there a simple how-to on how to test each battery separately? I don't expect the Autozone employee to have that JL-specific knowledge.

I try to avoid the dealer when possible. If the batteries are bad I'll bring it to them for replacements.

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[Fudster]

Temporarily disconnect all cables from the main battery's negative post.

Placing your tester on the positive and negative posts of the main battery will now only test the main battery.

Move your tester's negative test prong over to the dangling cables. This will test the ESS battery, even through the positive prong of your tester remains on the positive post of your main battery.

Reconnect all the cables to the negative post of the main battery after the test.

 

[Jebiruph]

The dealer is probably still going to test the batteries before they replace them and that usually means they have to have it long enough to make sure it's charged before they test.

 

[zrickety]

I'm taking my JL to Autozone to test the batteries. Is there a simple how-to on how to test each battery separately? I don't expect the Autozone employee to have that JL-specific knowledge.

I try to avoid the dealer when possible. If the batteries are bad I'll bring it to them for replacements.

You already have the diesel...pull that ESS battery, move a cable and permanently disable it.

I just did it as easily as I know of ……. Just bolt the positive cable from the auxiliary battery onto the main battery positive cable and disconnect the auxiliary negative cable from the main battery cable and tape it up , your done…….hardest part is fishing aux positive cable up to the main battery……

 

[mwilk012]

The only way idiots at auto zone will be able to actually test them is if you yank them and put them on the counter.

If you suspect the aux battery is bad, it probably is. Replace it.

 

[rickinAZ]

The only way idiots at auto zone will be able to actually test them is if you yank them and put them on the counter.

If you suspect the aux battery is bad, it probably is. Replace it.

I can be as skeptical as the next guy, but in this case, I trust them enough to have someone who has likely tested 100s of batteries perform a simple job. The alternative is to take it to the dealer, which is always iffy, at best, and time-consuming at least. The Jeep is still under warranty, and a DIY replacement would cost $300+, so I'd like a quick assessment before I take it into the dealer for warranty replacement. A DIY replacement would only take 15 minutes (thanks Jeep for making it easy on an Ecodiesel), but why spend $300 unnecessarily? The Jeep has less than 8,000 miles.

Under normal circumstances I would agree with you 100%.

 

[mwilk012]

I can be as skeptical as the next guy, but in this case, I trust them enough to have someone who has likely tested 100s of batteries perform a simple job. The alternative is to take it to the dealer, which is always iffy, at best, and time-consuming at least. The Jeep is still under warranty, and a DIY replacement would cost $300+, so I'd like a quick assessment before I take it into the dealer for warranty replacement. A DIY replacement would only take 15 minutes (thanks Jeep for making it easy on an Ecodiesel), but why spend $300 unnecessarily? The Jeep has less than 8,000 miles.

Under normal circumstances I would agree with you 100%.

They would have to disconnect both positive and negative cables to test them and get a somewhat accurate read.

 

[rickinAZ]

They would have to disconnect both positive and negative cables to test them and get a somewhat accurate read.

That was my take as well. If both cables are removed, and the battery tester is clipped to the (unconnected) cables, that should isolate the auxiliary battery for testing. Then, by clipping the tester to the main battery's terminals (standing alone, with no cables attached) that should isolate the main battery.

I am, at best, a shade tree mechanic. Are my assumptions correct for a process to evaluate without actually pulling the batteries in the Autozone parking lot?

 

[mwilk012]

That was my take as well. If both cables are removed, and the battery tester is clipped to the (unconnected) cables, that should isolate the auxiliary battery for testing. Then, by clipping the tester to the main battery's terminals (standing alone, with no cables attached) that should isolate the main battery.

I am, at best, a shade tree mechanic. Are my assumptions correct for a process to evaluate without actually pulling the batteries in the Autozone parking lot?

Sure, but if you are feeling the need to test the auxiliary battery, it’s easy enough to just replace it.

This method you’re describing works for now, but later on in the vehicles life the degradation of the cables and terminals can cause bad readings. Of course, they’ll only help it fail, so it’s not a big deal.

 

[rickinAZ]

Just got back from Autozone: bad voltage regulator.

 

[rickinAZ]

That was my take as well. If both cables are removed, and the battery tester is clipped to the (unconnected) cables, that should isolate the auxiliary battery for testing. Then, by clipping the tester to the main battery's terminals (standing alone, with no cables attached) that should isolate the main battery.

I am, at best, a shade tree mechanic. Are my assumptions correct for a process to evaluate without actually pulling the batteries in the Autozone parking lot?

BTW, this process worked like a charm without trying to segregate multiple individual cables. In my research on how to do it, some members seem too make this way to hard in terms of isolating the two batteries from each other.

Thanks everyone, for your input. I may still need new batteries (under warranty) but the unaddressed voltage regulator problem would have been the gift that keeps on giving.

 

[Initial-Jeep]

Direct Current (DC) requires a closed circuit (positive and negative); only one needs to be disconnected (negative/ground is safer).

It's just like a AA battery: there's no current flow when only one terminal is touched/connected. Fudster's procedure is effective.

 

[Fudster]

That was my take as well. If both cables are removed, and the battery tester is clipped to the (unconnected) cables, that should isolate the auxiliary battery for testing. Then, by clipping the tester to the main battery's terminals (standing alone, with no cables attached) that should isolate the main battery.

I am, at best, a shade tree mechanic. Are my assumptions correct for a process to evaluate without actually pulling the batteries in the Autozone parking lot?

As mentioned, you need only remove the cables from the negative post of the main battery.

@zrickety's advice about bypass the ESS battery is fine as long as you don't plan on running ESS. If you do, this advice could have you drain your main battery during ESS events and affect your ability to crank the vehicle thereafter.

When the vehicle is at rest the terminals of both batteries are connected. This is why when you remove all the cables from the negative post of the main battery, and put your tester on the main battery's positive post and the dangling cables, the only circuit is through the ESS battery, which is what is tested.

Put those testers on the main battery's posts with those negative cables from the main battery removed, and only the main battery is tested, as in this configuration the removal of the negative cables from the main battery's negative post takes the ESS battery out of the circuit.

Put your tester on the main battery's terminals with the wiring as per the factory and expect a composite voltage of both batteries from the tester.

 

[mwilk012]

Just got back from Autozone: bad voltage regulator.

Autozone cannot diagnose anything. How did they come to this conclusion?

 

[rickinAZ]

Autozone cannot diagnose anything. How did they come to this conclusion?

Mistakenly, I think.

The Jeep is running like a champ with it's two new warrantied batteries and it's original "faulty" (according to Autozone) voltage regulator.

You Autozone detractors may have been right all along.

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