Is my car battery dying ?

[GypsmJim]

A timely thread for me. Two days ago, I went to take my Lexus RX450h hybrid SUV to get its state inspection so I could renew its registration. The dash lit up, but it wouldn't start, so I decided to recharge the 12 volt battery with my trusty 45 year old Schauer charger. To avoid any problems from accidentally zapping the 450h's very complex electrical system, I decided to disconnect the battery, located in the trunk. Now Lexus did not make battery access a priority on the 450h. I had to: 1) Remove the trunk carpet mat, 2) Raise and fold the hard deck and fasten it to the rear seat with a hook, 3) Remove the spare tire cover, 4) Remove three plastic pop rivets from the battery cover, 5) Remove the battery cover, 6) Disconnect the battery, being careful not to dislodge the vent tube. I charged it for 45 minutes until the charging rate stabilized. My voltmeter showed 12 volts, close enough for me. Before I buttoned everything up, I attached a pair of quick connect leads to the terminal clamps that allow me to plug in my low-amp battery maintainer from outside the car. Now I can easily "top off" the battery as needed. I then charged the battery for a couple of more hours using the battery maintainer.

Yesterday, I went to get the inspection. My 450h fired right up and ran perfectly. I drove the three miles to the inspection station, and got right in, as there was no one ahead of me. The inspection went quickly, and... it failed! I still had to pay $25 for the inspection. It turns out that the car's OBD computer has to reset after a battery disconnect, and won't engage the inspection station's emissions computer until the car is driven about 30 miles following the reconnect. Nowhere in the owner's manual (yes, I read the owner's manual) was this mentioned. I learned it from the inspection station guy.

Today, I cruised up and down local highways until I'd put 35 miles on my 450h and returned to the inspection station. This time it passed! Even better, I didn't have to pay for the re-inspection. But what should have taken one afternoon had taken three days. Moral: If you live in a place where OBD computer emission inspections are required, make sure your battery is up to snuff before you go.

Been there done that. Same issue with me. However, I DID know about it and I DID drive the 35 miles, but it still had not reset. I waited till the end of the month and then it passed.

 

[GypsmJim]

My two vehicles 25+ and 45+ years old with AGMs. They came stock with flooded lead acid batteries and stock charging systems, well the truck has an upgraded alternator - both are doing fine and are about 3 years old.

AGM batteries are better in every way than a flooded lead acid battery and they DON'T LEAK!

I traditionally got about 6 years out of an auto battery and maybe 8 years out of a boat battery.

I got influenced by the Koolaid a number of years ago and replaced my boat battery with an AGM. Sounded good. Within 3 years I needed to replace other batteries. So, after 2 years I had AGMs in 2 cars, 3 boats and 2 tractors. Fine! Right?

In a 2 year period they all went bad. Since they all cost so much more, I was disappointed with the cost performance. At double the cost they should last twice as long.

Now I buy "sealed" Auto Zones. No fluid to check. The only AGM I still maintain is in a jetski, because of the jossling around they go thru. And I'm stuck with the AGM in my 2025 XT5, because that was OEM.

 

[LVSteve]

Some vehicles with deeply buried batteries have hidden lugs for jump starting. These lugs can be used for charging as well.
Check the owner's manual.

Yes, two of our cars have jump lugs in the engine compartment, remote from the battery. They can also be used for charging per the manuals. No amount of charging was saving my battery, in or out of the car.