CX-5 Battery Testing

[shooter357]

I was told today by the people that changed my oil that my battery was weak. I know how to test it with a multi-meter while cranking the engine. The engine can not start while doing this test and I was wondering if I pull fuse 3 which is labeled injector eng.sub does this disable the injectors so it won't start. I think so but am not sure. It's a 2019 so the battery is 3 years old. I remember when a battery would last @ 5 years.

 

[Conrad 16.5]

What's the voltage reading after the car has sat for a while, say overnight?

What's the reading while the car is running?

 

[HyFlyer]

...if I pull fuse 3 which is labeled injector eng.sub does this disable the injectors so it won't start...

If you hold accelerator pedal to the floor it does the same thing.

 

[CarpeDiem]

VOM readings are pretty useless, they don’t tell you the battery’s actual condition. For that a true load test is required, free at auto stores like Autozone. Don’t waste your time - use professional tools.

Vehicles today are not like those of the 20th century. So much is controlled by computers that even minor low voltage events can cause issues. The demands on batteries were much lower years ago, so they lasted longer. Too, local conditions effect battery life - high summer temps can shorten a battery’s life considerably.

 

[dunhillmc]

Took my 6 in for service yesterday and asked them to check the Mazda battery I put in 18 months ago. They hooked it up to the fancy battery tester and it immediately flashed FAILED. They replaced it under warranty

 

[Jmaz]

Took my 6 in for service yesterday and asked them to check the Mazda battery I put in 18 months ago. They hooked it up to the fancy battery tester and it immediately flashed FAILED. They replaced it under warranty

Was the Mazda battery that failed made by Panasonic. I'm running an OReilly Auto Superstart Premium (made by East Penn/Deka) that's 2 yr and 9 mo old. So far so good. Gonna see how long this one lasts. Original Panasonic was still functioning at 6 years old but weak cranking in cold weather.

 

[wlong01]

Not sure about these quick tests. I had my car in to the dealer for a battery problem (battery was replaced in Aug, started acting up in Nov). They ran some test on the battery that took about 45 minutes and came up with a bad cell. Voltage on the battery always showed normal.
Replaced the battery under warranty free.

 

[shooter357]

Battery voltage at rest after sitting is 12.5 volts. Alternator good putting out @ 13.5 volts running. I found the fuses to pull so engine wouldn't start and battery reads 10.5 while cranking. Battery seems good to me

 

[ColtX-5]

That should do it. But note that 12.5V is about a 75% State of Charge, so your battery is weak. A fully charged, healthy Pb-SO4 battery should show about 12.7V, depending on the alloys used.

 

[theblooms]

DMM's don't do diddly squat for checking the health of a battery. You have to use a load tester.

 

[wlong01]

Battery voltage at rest after sitting is 12.5 volts. Alternator good putting out @ 13.5 volts running. I found the fuses to pull so engine wouldn't start and battery reads 10.5 while cranking. Battery seems good to me

This was exactly how my battery was reading. It would start 99% of the time. Had 2 non-starts in a 4 month period. Initial quick tests said the battery was fine.
Only after deep test did bad cell show up.

 

[Conrad 16.5]

VOM readings are pretty useless, they don’t tell you the battery’s actual condition. For that a true load test is required, free at auto stores like Autozone. Don’t waste your time - use professional tools.

Vehicles today are not like those of the 20th century. So much is controlled by computers that even minor low voltage events can cause issues. The demands on batteries were much lower years ago, so they lasted longer. Too, local conditions effect battery life - high summer temps can shorten a battery’s life considerably.

I understand how a DMM works and that it can't load test a battery. It can still be a diagnostic tool if you're looking at the general health of a battery.

OP states that the battery reads 12.5vdc after sitting a while and 13.5vdc while running. Is that not diagnostic? Of course, it doesn't tell you all that you need to know but it at least tells you that the system is charging, and that the battery appears to be holding a charge.

 

[theblooms]

All those numbers tells you is that the alternator is working, which absolutely is important. But it tells you nothing about the battery itself.

 

[Conrad 16.5]

All those numbers tells you is that the alternator is working, which absolutely is important. But it tells you nothing about the battery itself.

That's more than he knew before checking with a DMM isn't it? Diagnostic.

 

[GAXIBM]

Battery voltage at rest after sitting is 12.5 volts. Alternator good putting out @ 13.5 volts running. I found the fuses to pull so engine wouldn't start and battery reads 10.5 while cranking. Battery seems good to me

10.5 while cranking is weak to me, volt meter is averaging slightly so it likely drops below 10 for an instant.