Auxiliary battery keeps dying

Using the Optima charger, I charged it to "Full," which was 12.5. Every night or in the morning, I'd check it using the same charger, and it was usually 12.3, sometimes 12.2 or 12.4. It was once 12.5 after I had to drive it for a minute to get the rear facing my garage. The charger called these charges 50%, except for two times that it said 75%. There have been no more non-starting incidents.
So it seems that regular use is keeping it in a usable range, but now I want to see if frequent charging will buff it back to a fuller state. I'm going to try charging it fully a few times a week and see if the numbers change.

 

12.5 is not "full". Your other numbers don't look too good either.

 

The test that determines the usefulness of your 12v battery is how far does it drop under load. Turning on the headlights should not cause it to drop more than 0.4 v and the voltage should recover quickly when the load is removed. If your Optima charger has a "desulfating" mode, use it to try revitalizing the battery to a higher SOC.

JeffD

 

The charger doesn't have a desulfating mode, per se. (If I was leaving it plugged in for a season, it would automatically do some kind of adjustment every thirty days.) But I think charging it to higher and higher voltage is supposed to help.
I've taken to charging it whenever it can stay plugged in for at least 12 hours, and the resting voltage is climbing. It now reports to be at 12.5 (calling it 75%) whenever I check it. I'll continue in this manner and keep reporting the results.

JeffD, can I do that headlight test using the HUD, or do I need to bring a multimeter to the battery?

 

Since the issue is the change in voltage under load, the HUD should be fine for a "under load" test.

JeffD

 

The headlight load test: It dropped .4 and then climbed to a .3 drop after a few seconds. With the headlights off, it jumped back to where it started. I repeated it a few times and it only dropped .3 after the first time. (The baseline was 12.1 V in this case.) So it passes that test.
I'm continuing with the more frequent, longer charging to see if it restores some power.

 

this is a lot of work, to maintain a 2 year old battery, that should be replaced under warranty.

 

In among the 27,720 posts you have made.......you do hit the nail on the head once in a while.

 

Agree with both comments.

"There is none so blind as them that do not see"

Your baseline is essentially a flat battery. At some point you will concede and replace your defective battery -- hopefully while it is still under warranty.

 

even a blind squirrel finds a nut once in a while.

 

I usually like your posts, this one, not so much. Hope it was something that I just misunderstood.

 

I think you understood it correctly.....probably.

 

The Maintenance mode of the MFD is adequate, but will tend to read a couple tenths of a volt lower than using a multimeter at the battery terminals.

JeffD

 

My car has been doing this for a while and now my 12V battery is dying repeatedly after leaving it for a couple days. Is there a list of errors somewhere to check for that would result in the long beeeeeeeeep when I lock my car? It only makes the beep with the FOB of course and now when I use the door button to lock...

Thank you!

 

welcome! maybe time to check your battery voltage.

 

Just wanted to chime in, documenting another JBL amplifier causing a parasitic load when the car is completely off - killing 2 auxiliary batteries. The car is a 2005 with 148,000 miles on it. This is the first problem (well, other than the traction battery failing at 125,000). It ended up leveling off at about 1.2A, but it was very inconsistent for a while. Maybe other functions of the computer and such, but I did wait the prescribed 20 minutes. The parasitic load would jump as high as 2 Amps, go down to 0.02 Amps for several seconds, then back up to 1.5-1.7 before leveling off at 1.2 Amps. When I checked the Amp it was very warm to the touch. Pulled the 30Amp fuse under the hood and BINGO! Draw dropped to 0.01A. Put it back in and 2 Amps. Take it out, 0.01 Amps.

Even though there is a documented manufacturers defect, and a TSB from Toyota with the JBL Amp, I opted for an eBay replacement with a 30 day warranty. I can verify it works correctly without it pulling power when the car if off. The original lasted 12 years, not ideal, but at this point hard to fault.

Again, just wanted to contribute as this was a tedious process even though I knew how to troubleshoot. If a dead auxiliary battery occurs overnight more than once, this is the first thing I would check. Of course, this only applies to models that have the JBL sound system.