Well, it's finally happened to us. We went on vacation for 2 weeks, got back tonight and our RZ450e (2023) wouldn't unlock with the card key or the fob. It didn't respond at all.

We used the emergency key but forgot about the manual handle near the front of the fixed door handle, if we ever knew about it. A call to Lexus support helped and got us in, but the car was still totally dead.

Thankfully, we keep a jump starter for situations like this, but we didn't find a way to manually open the trunk. So, I had to crawl to the back from the front, put the seats down and then open the sub trunk from the wrong side.

The jump starter still had 81% charge, thankfully. However, it wasn't a simple task to get the car started. When connecting the charger it would do clicks for about 15 seconds and then give up. We tried this several times. Eventually, I got it to the point where I was able to start the car and the high voltage system (which was at 72% SOC).

I made the mistake of plugging the L2 back in (we were in airport parking at LAX), which immediately turned the car off. I had to do the dance again with the jump starter to get the car going once again.

We drove straight home after this, not risking another stop. I put a battery maintainer on it, but it's only pulling 0.1W, so it's not a good sign.

I think the 12V battery will need to be replaced. I know others have had this issue. I will see what I can do tomorrow, but will probably have to go thru the jump starter dance again.

This was a very frustrating way to return home after flying for 16+ hours (2 flights and a 4 hour layover in Tokyo Haneda).

 



 

That is interesting there is a difference between the Japanese OEM battery and dealer provided replacement Lexus battery. Apparently the Lexus battery on the dealership is made by interstate.
My battery just broke at about the two-year mark and was replaced under warranty.

 

Thank you for your replies. I will show this to the dealer in about an hour. Hopefully, they won't give me any trouble.

 

Well, I took it in. They did the camera recall and gave me a NACS adapter, but not a new battery. They said it charged ok. They said just don't leave it for 2 weeks! Have someone drive it every week was their suggestion. Kind of hard to do when it's at airport parking.

I don't expect this will be the end of the 12V battery story. They should have replaced it. It's a known problem after all.

Is there an easy way to monitor the 12V voltage? I don't know of a gauge in the car...

 

I have a 2025 RX450h+ and a couple of months ago I got the dead 12v battery in my garage…just out of the blue…no warning. The car was being lightly used basically on plug in battery. It had last been driven about 3 days earlier, and the plug in battery was fully charged. I went to the car and opened the door, and the startup tines sounded corrupted, and went silent. Pushed start button, and nothing happened. Everything electrical was dead.

The dealership had a technician who was able to stop by and give me a jumpstart. When I took the car in for service, they just replaced the battery with an interstate battery. When I asked why the problem had occurred in the first place and I had no warning, I was just told that I should drive the car more. While it is true that I am a low mileage driver, just over 3000 miles in nine months of ownership, I did not find that to be a very good answer. For a car which monitors so much,it is very disappointing that it doesn’t do a better job of managing the 12 V battery status and providing early warning to the driver.

 

I've left our RZ300e sitting in the garage for 2-3 weeks at a time during summer vacations, with no ill effect.
I suspect your dealer is brushing you off instead of properly diagnosing whatever is wrong with the car that depletes 12V battery while parked. If possible, consider taking your concerns to another dealer in the area?

Not easily, and monitoring itself would deplete the battery faster!

Good luck,
a

 

When the drive battery is plugged in Lexus should have designed the 12v battery to also be trickled charged from the same plug. Alternatively, since trickle charging requires such little power, why not have the main battery, whether plugged in or not, continue charging the 12 v battery. Or am I missing something?

 

Sorry that was your experience. Did your dealership provide a video inspection?
My dealership actually hooked the battery to a load and battery diagnostic machine to test it.
Also there is a “hidden” diagnostic menu you can get into the head unit by doing some swipes on the screen when the display is off. Once you get in the menu you can see voltage levels. But if the battery is so dead and the head unit cannot turn on, it is essentially useless. Let me try to find the procedure.

 

Alright, this was a struggle. I had to take it in twice last week to the dealer. They replaced the battery the 2nd time, with a Lexus/Interstate one. At 1st they said it was ok as it was "taking a charge." However, with my testing it was losing 60% of its charge overnight. It probably would have died again in a few days.

Hopefully, all will be well until we can finally turn this RZ450e in!

Thank you all for your help.