Is my car battery dying ?

[BC38]

I had to replace the battery in my wife's SUV recently.
Came out one morning & it wouldn't crank.
Charged it up and all was good for a few days.
But after sitting unused for 2 or 3 days it was dead again.
Charged it up again and IIRC it was reading a steady 12.8 volts with my handheld meter.
I took it into the local Interstate Batteries warehouse (where I buy all my batteries) and had them load test it.
When they hooked it up and with no load it was still reading 12.8 volts - then the guy threw the switch to put a load on it.
It dropped immediately to 8.6 volts and immediately started dropping lower - fast.
The chart on the front of the load testing machine said that under load the voltage shouldn't go below 9.6 volts.
Sounds like yours is doing about the same - except that yours isn't even starting out with a charge above 12 volts - like it should.
Sounds like it's time to replace it.

 

[Bald1]

Replace your battery! Once you draw it down below 12 volts, you've basically killed it from holding a charge very long.

^^^^^^^ this. It’s a battery not a transmission. If you can’t or don’t want to do it, most auto parts stores will do it for you.

 

[gjgalligan]

For vehicles that sit outside try a cheap solar charger.

 

[TLflag]

Battery

A lady friend in Denver bought the big Subaru sedan. It's on its 5 battery now. The factory agent who responded last told her that the car has to be driven 32 miles each day or the battery will go flat because of all the fancy electronic features drawing power, even when sitting. So far that is still happing.

 

[Tom S.]

A lady friend in Denver bought the big Subaru sedan. It's on its 5 battery now. The factory agent who responded last told her that the car has to be driven 32 miles each day or the battery will go flat because of all the fancy electronic features drawing power, even when sitting. So far that is still happing.

Wow, that's just stupid! When running, the alternator should supply enough energy to power all the electronics plus keep the battery charged.

From Reddit:

1- Remove your DCM fuse. It’ll kill starlink, but impacts nothing else. 90% of the issue is parasitic drain from a faulty DCM. Replacement costs $800, and there’s no way I’m paying for that just for an SOS button.

2- Take it in to Subaru and have them perform the software update for your alternator after they confirm it is indeed the DCM causing the parasitic drain ($100 for parasitic drain test & alternator software update). It’s complicated, but basically the alternator was programmed from the factory to NOT fully charge your battery in order to save gas.

 

[SMSgt]

Battery shut-off switch like Caterpillar installs on bulldozers will fix it.

 

[BC38]

Battery shut-off switch like Caterpillar installs on bulldozers will fix it.

Yeah, but you'll lose all your radio settings, and any other customizable features and settings.

 

[Ματθιας]

Wow, that's just stupid! When running, the alternator should supply enough energy to power all the electronics plus keep the battery charged.

From Reddit:

1- Remove your DCM fuse. It’ll kill starlink, but impacts nothing else. 90% of the issue is parasitic drain from a faulty DCM. Replacement costs $800, and there’s no way I’m paying for that just for an SOS button.

2- Take it in to Subaru and have them perform the software update for your alternator after they confirm it is indeed the DCM causing the parasitic drain ($100 for parasitic drain test & alternator software update). It’s complicated, but basically the alternator was programmed from the factory to NOT fully charge your battery in order to save gas.

Wasting a whole day taking a vehicle to the dealership to program the alternator!? Really!?

Yeah, no. And some people wonder why I refuse to buy a new vehicle.

 

[TX-Dennis]

Yes, your battery is almost assuredly bad.

I just replaced the battery in the wife's Lincoln a couple of days ago. $270 OTD. 3 year warranty. AGM group 94. Hers was 5 years old, and she was getting messages on the screen that all accessories were disabled due to low battery charge. She wanted me to charge it, but I said it's 5 years old. We got our money's worth out of it. Time for a new one.

I had put a jump box in her car until I had time to replace it - just in case. I told her I didn't want her to be stranded somewhere. She reminded me that she would have no idea what to do with it. Valid point, I suppose.

 

[soFlaNative]

Loaded my lil' truck for the Thanksgiving trip to Mom's and needed the jump box on the wife's '17 Tuscon to move her out of the way one day after hearing the starter skip a beat. Three days later I was cussing at the recessed positive terminal trying to get a bite with my cables after the jump box, even with the boost feature failed to work. While the alarm kept lighting off.
Praying I had a connection she tried to crank and I kept a fast idle from my truck for a few until she fired up. Quick trip to an Auto Zone and $240 for a mid range 3 year. The installer suggested to return a few months before the expiration, 85% of full guarantees a swap even if they bother to check. I'm not completely OK but I'll sideline my morals to avoid my wife having to deal with the situation down the line.

 

[pasound]

Your battery is going bad. My local mechanic says to never buy a battery from the chain stores. Their house brands are always the cheapest ones, but that's because they are cheap, and poor quality.

 

[soFlaNative]

My local mechanic says to never buy a battery from the chain stores. Their house brands are always the cheapest ones, but that's because they are cheap, and poor quality.

As an expert can he recommend a source or merely quibble?

 

[Greyman50]

FWIW, unfortunately many forget Basic Battery Maintenance. Wipe the Top of the Battery Clean as build up can link + to - terminals resulting in discharge. Keep terminals and connecters clean and slightly greased to prevent corrosion. Many “ newer” vehicles have rubber covers attached to cables. Make sure you inspect them and clean as needed and cover terminals.

 

[ladder13]

I got about 7-8 years out of my C6 OEM battery, it was always on a Tender. Yeah, should have changed it but it started every time the button was pushed. One day it just died. I tried everything for two days to get it started, power pack, jumper cables, etc.

Called AAA, they came to my house, hooked up their cables, voila, lights camera action and off I went straight to get a new Interstate installed. The OEM had a dead cell.

 

[steelslaver]

Replaced 4 batteries this year, the 2 in my truck (diesel), one Lincoln and the Polaris Ranger. The old 7.3 hate to start in the cold, but I have a trickle charger wired in with the block heater.

 

[Tom S.]

Wasting a whole day taking a vehicle to the dealership to program the alternator!? Really!?

Yeah, no. And some people wonder why I refuse to buy a new vehicle.

I wouldn't waste a day either. Instead, I drop off the vehicle, hop in the loaner they have waiting for me and go on my way until they are done with my vehicle. Since my dealer is about 10 minutes from my house, it's not much of a waste.

 

[Pisgah]

I bought three top-of-the-line batteries in 2024; all 3 failed within the first two weeks after being installed. Yes, all were replaced free under warranty. but it is an indication of how severely lousy batteries have become. My only recommendation for battery-buyers? Buy the one with the best warranty, 'cause you will need it.

 

[dockmurgw]

Forget keeping the battery charged...just use the pull start, that's the little rope that hangs under the front bumper.

 

[WR Moore]

From Reddit:

1- Remove your DCM fuse. It’ll kill starlink, but impacts nothing else. 90% of the issue is parasitic drain from a faulty DCM. Replacement costs $800, and there’s no way I’m paying for that just for an SOS button.

OK, I've gotta ask: What's a DCM?

Yet another reason to keep our older cars.

 

[dockmurgw]

I know of two vehicles that suffer from battery drain...both Toyotas with aftermarket car starters.