When you drive it how far do you go? Short trips are hard on batteries. And yes, the battery discharges when parked because of the electronics. How long it would take to discharge so it won't start, I don't know. This may not be your issue.

I don't drive our Avalon much in winter so I keep a battery tender on it. You can get one at Walmart for about $30.

I would go to place that sells batteries and have them load test it after you have driven it for a half hour.

 

Thanks arh! The car is usually driven 10 miles or less each way. The dealer has put the battery on its Toyota battery tester and said it is definitely not the battery. I'm assuming they load tested it.

Several people have said we just don't drive the car enough, about 2300 miles in 9 months. This car is primarily my wife's and her last car was an '02 Camry and we never had a dead battery issue with it.

I think I'll follow your lead and get a battery tender.

Thanks. Jim

 

At most dealerships there are two ways to test a battery. Ask which test your dealer performed when they said your battery was okay.

The first is quick check with a battery meter that tells the current state of the battery. Don't accept this as a reliable test.
The second, and the one you want done, can take 1- 2 hours and really load tests the battery.

So, be prepared for a couple of hours at the Dealer and demand they do a load test using a Midtronics GRX-3590 Diagnostic Battery Charger or equivalent.

 

Also Sears used to have a load test that took about 30 minutes.
Don't take a voltage output test as adequate.


AAA might be a source also

 

I had dead battery issues within 20k-30k miles. Dealership replaced with a new battery at 35k then at 39k I left the car for 4 days and it didn't start again. After jumping it and taking back to dealership They said bad cell in battery and replaced it again. I'm suspicious that something is really wrong. I don't leave anything on like lights or doors open. Any one having these issues?


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The battery for your 2015 has had to be replaced like what, 3 times?! Sounds like an issue to me. Not that this helps your situation, but I've left my car unattended for several days on multiple occasions but have never had a battery issue. On one occasion I left it for 15 days. I have a hybrid but I don't think it should matter. Your relatively new battery should still be able to start your car after only sitting idle for 4 days. Something is drawing power...

 

Yes the milage shows low usage/short trips but from my experience these batteries are no good.
The battery in my 2014 avalon lasted I think 6 months with average milage. I started a thread about it.
I have not had good luck with my oem batteries. Now I have a odyssey agm battery for reliability.... well that and for my car audio needs

 

I have 2 years experience with this. Mine only does this beginning in December. Then if I fully charge the battery it will do ok until about the end of January or beginning Feb. One last charge for the winter and it will be ok until next December. Something to do with the cold garage aggravating the issue. Never does it in the Spring, Summer or Fall. Like you, mine only get driven perhaps 10 miles a day so I think it just isn't long enough to bring the battery back to full charge.

The dealer put a new battery in last year and it still ran down on its own this Winter. So I tried a little experiment, I put a voltmeter on the battery and tested it every night before I went to bed. And the battery would loose about .1 volts per day, so going from say 12.5 volts down to about 10.5 (where the car will not start) would theoretically take around 20 days to deplete. I think the only reason I get 30-40 days on a charge is because I do occasionally take it out on the highway for a few miles and this will add a little more charge to it.

I don't like it either but the only alternative is to buy one of those trickle chargers and plug the car in every time you put her to bed. I know if I do this, my wife will drive off with the charger connected the first time she used it.