When my battery went dead about a month ago after sitting for a little over a week, the Lexus dealer told me I probably left an interior light on. I know that I didn't, but I also know that the interior lights go off after 20 minutes (it's in the owner's manual, and I tested it after I got my car back). I still don't know why the battery died after driving the car for two months. If the battery was discharged from sitting on the lot for a couple of months wouldn't the dead battery have happened sooner? I also was wondering if using the 'auto' mode for the headlights and DRL's could have an impact. When I come home and pull into the garage, the headlights come on since it's a little dark in there. If I open the trunk to unload groceries, for example, the headlights stay on until several minutes after the trunk is closed. That might total 5-10 minutes. I am probably being too ****, but there must have been a reason. I can't believe a battery wouldn't stay charged for at least a couple of weeks.

So far I have not had any repeat dead battery issues, but I have only had the car sitting for no more than 4-5 days. I am a bit concerned since it's our only car and if we were leaving for an important appointment (we are retired so no work), it would be an even bigger issue - and no ride share where we live either.

 

For those of us who've had battery issues with recently purchased '20s, perhaps the Kentucky plant received a batch of bad batteries.

 

Perhaps, but my dealer told me the battery in my car tested okay once it was charged after driving the 25 miles to the dealer. No bad cells. Maybe a battery can test okay, but just be weak??

 

Just test the SOC of the battery yourself. Don’t need to waste time driving around or going to the dealer. All you need is a multimeter and battery charger. Simple.

 

Mine was a bad cell.

I think that testing equipment can be erratic. When I took my RX in 2 weeks ago, its battery tested around 580 CCA. Yesterday when I took it in it tested around 620 CCA. The OEM battery isn't even rated that high, so I question the equipment . . . .

 

Purchased a 2020 ES350 F-Sport a couple months back. This past Monday, my battery was completely dead and I couldn’t start the vehicle or even pop the trunk. Called Lexus roadside and they came over and jumped the battery then I took it to the dealer. They checked it out and determined there was no parasitic drain and fully charged it and said everything was ok and that I probably didn’t close the door (that didn’t happen). Now I have not driven the vehicle since Monday PM but have been measuring the battery discharge. If anyone knows, is it reasonable for the battery to discharge from fully charged (presumably 12.6V) to what will be under 12V tomorrow morning. And at what voltage will the ES not start. I asked the dealership these questions with a less than usable response other than the car has many electronic systems that still draw power when the car is off. This all happened with 670 miles on the car. I could get a charging pack and a battery charger and carry them around but I expect more from Lexus considering this is my 7th Lexus and have never had a problem. Can anyone shed some light on if it’s reasonable for the battery to discharge .6V in less than 3 days while sitting in the garage. I’m taking it back to the dealer tomorrow to attempt to get some usable answers.

 

Simple tests often do not show battery problems. They need to test it under load. My local Lexus dealer has the equipment to do this, some others might not.

 

I also use the Auto headlight function, but after I park my car in the garage I lock the doors. My mirrors fold and the headlights go off...are you in the habit of locking your car?

 

Hi Steve...In response to your question I too am concerned about battery drain even though I have not had a dead battery. Mine is a 2020 ES 300h UL which doesn't use the 12v battery for starting except just to power electronics to be able to start car. Purchased in December and reading about battery issues I measured mine and do see that after 2 days it drops from 12.6 to below 12 which does concern me. Their are a lot of electronics that are draining the battery and I am thinking especially the DCM module might constantly communicate transmit and receive periodically. It could be that all the problems they are having with remote start communications that the DCM tries to communicate more than normal during standby. Leaving a door open would not be a problem because it is a smart system and will cut off lights after awhile. I have not measured my current drain yet but it would be nice to know what Lexus says is standard current drain. I have seen my battery down as low as 11.76 after a week of not driving and if not a hybrid don't know if starting would be a problem. When you go back to Lexus ask them what is standard standby drain and then you can check it yourself at home. Please report back what their manual states standby drain should be. I am thinking about keeping jumper cables in my car.

 

When you start getting to 12V and under when parked, that battery is not great. Cant say for a hybrid, but on a gas car where you need to use that battery to start it thats not great.

 

Reading the various posts from members with brand new cars and dead batteries, it is not normal. Even if your battery is dead and then jumped to start, if you drive 25 miles the battery should charge if it is a good one. Batteries shouldn't discharge after a week of sitting. Even after 2 weeks of sitting. And you are correct packman that the interior lights shut themselves off
after a period of time. The dealer is blowing smoke at you and hoping that you buy his BS... Something is not right if the battery is totally discharging after a week. I've left my car for 3 weeks in the winter in an unheated garage while in Europe and came home to start it right up. Same with my Corvette.

 

I have to wonder about something here and hopefully someone knows the answer. If you lock the car, will it use more battery power because it is "listening" to sense when the smart key nears the vehicle. It is obvious to me that the car isn't looking for your key when it isn't locked because you can approach the car and nothing happens, yet when the car is locked and you approach the vehicle the interior lights and puddle lamps turn on. Just from a rudimentary observation it seems like the car might draw more power while it is locked. Many people cannot store their car in a locked/secured space so that certainly doesn't excuse the issue, but it might explain why some people are seeing the issue while others are not? Just pure speculation on my part.

 

The issue is if they've been discharged completely many times they wont ever hold a charge right again. When cars are new, they are quite often discharged and jumped and charged by the dealer or transport companies, etc and this can happen.

 

I do not lock the car at home as it is always garaged. My dealer said they checked the vehicle over a weekend and found NO drain on the battery. I guess my best plan is to see if it happens again. If it does, I will insist on a battery replacement.

 

The answer you're looking for can be found in paragraph 3-2 Battery-saving function section of the Owner's Manual (or at least that's where it is at in the 2019 ES350 version). Depending upon circumstances criteria, there are 10 minute, 5 day, and 14 day battery saving timing gates on the smart key system. Also, right after that section, there are directions on how to manually set the remote key fob electronic key into a fob's battery saving mode where the fob no longer expends battery power by no longer receiving radio waves.