Auto Zone battery testing…

[homerj]

I’ve got a 2015 Chevy Cruze that has recently developed an issue. Some days it’s pretty sluggish to crank, as if the battery is weak, while other days it cranks right up. Monday night i had to leave it running while i was working because earlier it had just barely started. Yesterday & today it cranked up right away. I figured it was just the battery so i went to Auto Zone to get one but before i did i got them to test the old one. They said the battery & alternator were good. If it’s neither of them then i don’t know what else it might be. How reliable is their testing?

[Levi]

Not sure how it is out there, but I wouldn't trust most the parts store folks out here. If you haven't done so already, you should clean your battery terminals.

[coyote]

I've had starter issues in the past that presented symptoms similar to your description.

[homerj]

Really? All the starters I’ve ever had go bad were all or nothing. Either it would engage & the vehicle would crank right up or it wouldn’t even attempt to turn the engine over.

[coyote]

Might have been the ignition relay. I'm trying to recall a problem from 20 years ago. I'm having the memory gaps and failures that accompany that situation.

[SignOfZeta]

My only advice is to make sure the battery is fully charged with an actual charger, preferably “smart” completely disconnected from the vehicle. Then install it and see if you get the issue again.

Modern vehicle ECUs are programmed to not overcharge batteries. Sometimes this can result in them undercharging. It assumes a battery is %100 and then applies its charging map to that. If you give it a %80 charged battery it may starve itself and leave you stuck somewhere.

Watching ECU voltage on a scan tool can give you some insight as to this phenomenon.

[markdem]

Ive never had a good experience with battery testers. Even the ones used by genuine dealerships.

[Chappy]

If you have a bad cell then it will only be a problem intermittently and can be difficult to catch with a test.

[homerj]

That’s kind of where i was leaning.

[Melrosejedi]

Check your cable connections for corosion also.a cheap digital multi meter can check the alternator output to the battery while idling. Normal output should be 13-14 volts.

[homerj]

Everything is nice & clean. Vehicle info center says low 14’s driving & low-mid 14’s idling.

[pghp8ntballer]

I second Zeta, Chappy, and Melrosejedi. Corrosion could be a problem. If the terminals look clean, was the battery replaced at any point? It could be a loose terminal or one that is not properly seated. Standard top post battery terminals are tapered. If it’s a GM side post battery, there usually isn’t much threading and they can work loose. If it has a bad cell, it can be fine one day, stone cold dead an hour later, and be magically ok another hour later. When it has a bad cell and starts fine it will test good.

High heat can wreak havoc on a battery just like very low temps can.

[Jordan]

Intermittent parasitic draw is also a possibility. Definitely check grounds, battery connections, etc.

[Trbo323]

How old is the battery?

I'm assuming it's standard flooded, have you checked the cells for fluid level?

Sent from my motorola edge 5G UW (2021) using Tapatalk

[BretG]

Get a charging indicator and monitor the the voltage as you drive the car. They have ones that plug into the power outlets.
Or, you can get a new battery and find out it's the alternator and then get a new one and find out it's the starter. Then you can learn it's the PCM. I had to mount an external voltage regulator on a Dodge Stratus once because the internal regulator failed.

[Chuck E Ducky]

It’s likely a connection corrosion issue. Check your connections including the ones on your alternator. Using dielectric grease at connection points.

How old is your battery? Should have a date on the top of it.

Also, your alternator won’t really charge unless you’re driving so letting it idle isn’t really charging the battery all that much.

The machines they use to test a battery are fairly reliable. It could be a dead cell or I have seen posts come lose from people tapping the cable connectors on with hammers. But I would bet it’s a lose connector they get stretched out and corrode often.

[Number six]

Short trips every day don't give the alternator a chance to recharge the battery from the starts. That's prolly why leaving it running helped the next time you started it. Take her on a 20 minute drive, or sit in it with the a/c going for a while. If the problem comes back, maybe the battery is starting to get a bit weak. Take it out and get a second opinion, if it's convenient. If the battery is bad, the alternator will wear itself out trying to keep everything going until it goes. Same with the battery hooked to a bad alternator.

[homerj]

Battery posts & clamps are clean & tight. I forget when i replaced the battery last. Can’t tell without taking it out. I’m thinking at least 3 years ago. I wish i could replicate the problem but the last couple of days it’s been fine.

[gabe]

Do a simple load test. You can either hook a multimeter to the terminals and check voltage while cranking (shouldn't drop more than a couple volts) or get a load tester from amazon. The last one I bought was only $40 or so.