Hello everyone!
Thanksgiving is right around the corner and turkeys aren’t so happy about that, so am I about how quickly my car’s battery dies during short inactivity.
Comparing to the rest of cars in our family, the Lexus battery despite being brand new will die within about 4-5 days of inactivity, whereas the rest of cars can go much longer exceeding over 2 weeks
What gives ?
Either Lexus did not do a good job with their electronics or you have a parasitic current drain.
A parasitic drain is usually from some electronic component that develops a short or refuses to “go to sleep” when the car shuts off. The first is typically a failure of the part. The second can be a part or a software failure.
Some electronics in cars continue to draw significant current after you turn off the key to be ready to start up if it thinks you are nearby. If you leave your keys close to where the car is parked unlocked - on a hook just inside the house from the garage, for example - the electronics will never go to sleep and drop their draw down to a level low enough to keep the battery alive. Sometimes locking the car will help that and sometimes not even locking helps and you need to put the keys in a metal box or farther away.
Try the locking and key things first. If that doesn’t work, a mechanic can run a parasitic draw test.
Has it always done this, or is this something new it is doing??
Did you replace the old battery due to this??
Is it only doing this since you had the new battery installed??
Have the new battery checked to make sure it is not defective, it happens…
Mustangman covered the parasitic draw part of it quite well…
Also the weakest link: the alternator.
After 3 remanufactured ones in my ‘81 Buick back in college, I finally landed one that cured what Clueless is experiencing.
Do you leave anything at all.plugged into your USB or 12v power ports overnight?
Do leave something connected to the 16pin DLC?
Welcome back! Are you driving again or is this inactivity because the car remains parked while you recover? When you say the batteries is brand new, do you mean it was installed in this couple of weeks or that it is several months old? Another possibility is that the battery is defective. On a car I owned 10 years ago, the battery died and I had two defective replacements. You might get the battery checked as part of your troubleshooting.
Thank you, jtsanders.
The car is temporarily given to my relatives while I try to recover from a devastating health crisis. The relatives are the ones who told me the battery keeps dying despite the car being driven occasionally.
The battery was replaced on July 9th, 2025.
They told me the car is completely off when they turn it off. Nothing in the USB ports.
As for my health goes, it doesn’t look promising. I’m not cleared to drive, neither do I feel like I want to. I’m at a very dark stage of my life but the doctors told me not to give up just yet. 
Then it should be covered by warranty.
I’m very sorry to hear that. As your doctors said, try to remain positive and hopeful.
They need to use a battery charger/battery tender. Most people use their vehicle an hour each day; 20 to 30 minutes each way driving to work plus other driving. Minimum driving should be 1 hour each week.
After the battery has become discharged to the point it will go dead in 4 to 5 days, it can take up to 12 hours to recharge. Ask your relative to drive to Chicago and back, if that is inconvenient use a battery charger.
USB ports are powered by the radio, those are not a consideration. Power outlets are off when the ignition is off.
There is a labor operation code to pay the technician 0.3/hour to recharge the battery, but it is unlikely the vehicle will leave with a fully charged battery. The tech will leave the test equipment connected just long enough to get a pass/fail report.
Our lube techs kept an old battery under the bench to use for a “failed” test report, this gave them the justification to replace discharged batteries. That ended after corporate performed an audit to see why so many batteries were being replaced.
That is just plain evil of them.
The love of money….
Who is “them”? Corporate auditor, the customer or the technician?
Batteries sold by Lexus dealers have a 2-year free replacement warranty, customers expect a free battery every time they let their battery go dead, typically after 6 to 12 months of storage.
Perhaps whoever instructed the techs to keep that ‘spare’ battery there.
+1
Sorry to hear that, hang in there the best you can sir…
You will be in our thoughts…
I like @Nevada_545’s suggestion of a battery tender if you have a 110V outlet handy. IIRC you live in a condo/apartment and might not have an electrical outlet available. If you do, then your relatives won’t have to drive as often.
Hang in there. I will hope for stabilization and eventual recovery too.