Napa AGM CCA dropped 10% after 2 months

[ibx1]

Purchased a NAPA The Legend Premium AGM Battery, group size 48 on November 27, 2023, to replace the stock AGM battery that came in my Honda Pilot 2017. The battery is rated for 760 CCA.

When I purchased the battery it has a shipping label of 8/23, and has some dust on top of it.
I guess it was an old stock, but it was 20 mins before my NAPA store closing time, and winter storm was coming in a day.
I just decided to accept it.

At home, I tested the battery using my Fluke 117, and it was giving a reading of about 12.3 volts.
Charged the battery inside the house for 3 hrs using my Schumacher in AGM setting until it reaches 99%, and unplugged the the charger.
In the morning I tested the battery, still unplugged, and I got 12.9 volt, and 855 CCA. Ambient temperature inside the house was about 70 F.

Installed the battery in the car, and everything was fine. The car is always park outside, and it is located in high desert Utah, where during normal winter, temperature can dropped to about 25 F.
I decided to test the battery health 2 months later, after the battery has gone thru several weeks of cold temperature cycles and probably about 200 start stop cycles, going around to office, store and so on. Average each trip usually is only 5 mins to 12 mins.
I got a reading of 712 CCA, which is a drop of about 9.3% from the stated 760 CCA on the label.
I tested the battery when the ambient temperature was about 40 F to 50 F, and car has been warmed up after some driving.

The battery state of charge was also only 80%. Honda alternator for some reason only keeps the battery at about 80% charge, possibly because my short commute. I topped off the battery charge while connected in the car using Schumacher, up to 100%, but SOH remains at 710 to 712 CCA

The car starts fine without issue, even during the coldest morning.
Honda "factory" CCA is at 650 CCA.
The car started fine even with the old Johnson Control factory battery, which was tested, then at 385 CCA.

Is this normal behavior for the battery's SOH to drop 9% in just 2 months, or maybe I get a defective battery?
I thought Cold Cranking Amp is rated at 0F. Ambient temperature was nowhere at 0F.

 

[SubLGT]

It is very possible your battery tester has poor precision. If you take 6 measurements one minute apart, and turn the tester off/on between each measurement, how much variability do you see in the CCA measurements?

 

[f355spider]

I wouldn't worry about it, yet. You have a three year replacement warranty and it isn't even close to an issue yet. Wait a year and if it continues to drop, get them to replace it.

 

[f355spider]

It is very possible your battery tester has poor precision. If you take 6 measurements one minute apart, and turn the tester off/on between each measurement, how much variability do you see in the CCA measurements?

Also readjust the clamps. I have found clamping pressure and where you clamp to, can make a significant change in the readings.

 

[SubLGT]

Also readjust the clamps.

YES! I forgot to mention that.

 

[The Critic]

I wouldn't worry about it, yet. You have a three year replacement warranty and it isn't even close to an issue yet. Wait a year and if it continues to drop, get them to replace it.

They won't replace unless the measured CCA is below the failure threshold.

 

[f355spider]

They won't replace unless the measured CCA is below the failure threshold.

Of course.

 

[SC Maintenance]

Your testing process is flawed.

First, you can not test when the battery is @12.9V because that is a residual over-voltage from charging and your test results will be wrong. You need to stop charging then let it sit for 24 hours, or you can let it sit for 30 minutes and put a small load on it for 30 seconds - like turn the headlights on for a bit. Either way the voltage should be pretty close to 12.6V when testing - anything more is a residual.

Voltage testing is a rule of thumb, not a test. I have had batteries that will hold 12.6V forever and others that won't do much over 12.4 and it didn't seem to matter, so long as it was steady and held there.

Resistance is another piece of the puzzle. The lower the better - new battery I would expect to be under 4 milli ohms.

None of this matters in the end because they won't replace it until it drops below about 60% of rated CCA - when tested correctly. You bought it, you own it. I now test the battery at walmart before I buy it.

 

[eljefino]

This is obsessive behavior that comes from owning a tool that gives precise-looking numbers. We never used to have these testers, so we didn't worry. A carbon pile tester is better. Midtronics says not to use their tester on new batteries, as you'll get a false positive reading that's above the battery sticker. In my experience 10-15%. So you got the "normal drop" on a battery that's been used a bit. I bet it plateaus here for a while. As for the initial battery health, as you noticed, it could have been better.

 

[SC Maintenance]

The issue is not the cheap tester, but the lack of detailed instructions on its use. I have a cheap tester, and its been very helpful. You need to understand its limitations.

The biggest issue is batteries have no rating except CCA. Testing CCA at anything other than 0F is going to give highly suspect data, even if the tester is supposed to offset for it. However as you pointed out - it should test well above the CCA rating while when new and above 0F. So knowing this, you can judge whether a new battery likely meets spec.

Testing the battery while hooked to the car, even if the draw is miniscule - is another source of error.

Also the fact the tester gives you idiot lights - like 'Good recharge", or "replace" are some mid point number programmed in that make it even more confusing for the owner, even if the data is accurate.

I portend that the big issue is the manufactures over-rate these batteries for marketing reasons. OEM batteries tend to have a much lower and more realistic number.

 

[eljefino]

The Midtronics testers have IR Ports that read the battery temp and (try to) correct for it.

The computerized ones not equipped for IR have a temp they're programmed to work at, and it doesn't have to be 0F. Hopefully it's documented in the manual.

You only really "need" to be at zero if you're using a carbon pile and re-creating the 30-second conditions that meet the definition of what a cold-cranking amp, is.

 

[SubLGT]

You only really "need" to be at zero if you're using a carbon pile and re-creating the 30-second conditions that meet the definition of what a cold-cranking amp, is.

And to complicate things, there are at least 3 definitions of what a CCA is: SAE, IEC, and DIN.

BU-902a: How to Measure CCA

BU meta description needed...

batteryuniversity.com

 

[benjy]

one thing for sure, once activated ANY battery is slowly degrading if NOT charged periodically!!