12 Vlt Battery Failure .. RX450H+

[Albeelexus]

The 12 vlt battery recently died on my 3 mnths old (1200 miles) RX450H+.

The dealer (excellent customer care ) picked up my vehicle .. replaced the battery but claim they're not  sure what caused  the battery failure since this is a new vehicle, being monitored for quirks and reliability issues.

This is a lovely vehicle backed by Toyota reliability.  Hopefully  this is a glitch and not a RX450H+ issue.

Ive purchased a Jumpstart battery pack in case this re-occurs and wondering if others may have had similar experience. 

 

BTW ..for info ..I was strongly advised by tow-truck 

 1)  Not to jumpstart vehicle from the fuse box under the hood. (only from battery terminals in the trunk)

2)  Avoid grounding connections near the Hybrid electronics (drivers side) under the hood.🙂

 

 

 

 

 

 

 

 

[RX400h06]

The dealership tech should've determined the root cause of the battery drain. Failing to do so could result in another drained battery. Hopefully, the original battery was defective or you were doing mostly short trips that can prevent the battery from getting fully charged. Then again, the hybrid battery may assist in charging the 12V one.

[Albeelexus]

RX400h06 .. The puzzle continues 😕.

The only addition to the vehicle is a 2 X channel (Think-ware) dashcam system supported by its own dedicated battery. The dashcam installation was transferred from my 2020 Lexus which had no battery failures.

The dealer (Dar-cars) claim they are monitoring for similar RX450H+ failures. 

I do not believe the hybrid battery assists in charging the 12V one. I read somewhere that the RX450H+ charging system may not operate sufficiently to recharge the 12V or dashcam batteries when the vehicle is in "Idle-neutral" or when "started remotely". 

Guess Its a game of wait and see ...while having JumpStart protection ... 

Cheers 🙂

[McBrian]

Always RTFM for the correct jumping procedure for your car. Tow truck drivers are the furthest from accurate knowledge or care for your vehicle. Their life consists of moving your car about maybe 20' in either direction and then driving away with no more thought of you or your problem or any damage they might have caused.

Typically the 12v systems are for everything else. Hybrid battery just supports that system.

As for add-on electronics, if that camera is indeed on its own system and not wired to ANYTHING else in the car, you have good argument for 'this isn't the problem' - All bets are off if it is clipped into any of the car's systems. Previous success does not equate to putting something known into a new system.

The "should've" with the dealership is absolutely true, but that would require they keep your car for weeks doing load testing and gathering data. Warranty or the dealership isn't going to pay the tech for that time and I don't think you'd want to see that bill.

Totally plausible this could be a fluke battery failure. The auto battery technology is still about 10 years away from being even remotely trouble-free. It's still a zeitgeist thing and we've been lucky so far with this "trend." Well... Ask anyone who has seen the bill for a hybrid battery replacement. Maybe not so lucky...

[Carbuff2]

12V battery failures, while not widespread, are reported here and there. Lexus/Toyota  has replaced MANY 12V batteries on their later hybrids. 😒

 

One contributing cause might be a FOB that is too close to the car. Keep it 25-30 feet away, or in a Faraday bag, so that it does not keep trying to connect to the car.

 

++++++++++++++

 

Also, familiarize your self (and other drivers) of the proper jump starting procedures and places to connect.  Many jumper-boxes do not have long enough connectors to prevent damage to the car's ECU if jumped improperly...and Lexus will not repair ECU damage for free! Even when their contracted Road Service providers do it wrong! 🤑

[McBrian]

The fob thing is 100% true and thank you for remembering that! Obscure truth right there!

I'm wondering as well how many of those 12s are just old stock on the shelves that are new but never used and at end of (shelf) life?

We made it a PDI line when I was at Ferrari and Subaru just for that reason. Started as a joke, but was better preventative than to deliver new cars with near dying batteries. If F-Cars were delivered with a FIAMM we immediately removed it. Helped CSI more than we'd have thought.

[Albeelexus]

4 hours ago, McBrian said:

 

 

 

 

 

[SandyBeattie]

The battery of my Lexus (with less than 10,000 miles on it) died while I was on a ferry boat.  It had to be moved for the safety and function of the ferry. The workers on the ferry attempted to get it started using the fob and then jumping it from the front and then from the back. Nothing worked. Eventually, a tow truck had to drive on the ferry boat after we rode it across the water one way and then back again the other way. The tow truck had to take me hours to get back to a dealer. At which point the dealer said I will have to pay for it because it was jumped incorrectly. While we were attempting to jump it, I called Lexus Roadside Assistance and had them talk to the workers who were trying to jump it. When that didn’t work, I called Lexus service department and had them talk to the workers who tried to jump it.  I had driven an hour to get to the ferry boat. While on the ferry boat, I had the car completely turned off and yet it’s spontaneously locked and unlocked the doors several times.  I don’t know why the 12 V battery did not charge during that drive or what was going on with the door unlocking. I’m very frustrated that my new car which I bought for the purpose of having a highly reliable vehicle is already unreliable and got me stuck in a very stressful situation. I’m even more frustrated that the dealership is not going to take care of it for me.

[RX400h06]

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That sounds like an incredibly frustrating and stressful experience, especially with a brand-new vehicle that’s supposed to be reliable. You're not alone—there have been reports of battery issues with the 2024 Lexus RX450h, particularly with the 12V battery not charging properly. Some owners have found that the hybrid system doesn’t sufficiently charge the 12V battery, leading to unexpected failures.

A few possible causes for your situation:

• Hybrid Battery Charging Issues: Unlike traditional gas-powered cars, hybrids rely on their high-voltage traction battery to charge the 12V battery, but some Lexus models have been reported to not charge it effectively.
• Parasitic Drain: Some owners have noted that certain electrical components continue to draw power even when the car is off, which could explain the spontaneous locking/unlocking you experienced.
• Jump-Starting Sensitivity: Lexus hybrids can be tricky to jump-start, and if done incorrectly, it can cause further issues. Some owners have reported that jump-starting from the wrong terminals can damage the system.
• Software or Electrical Glitches: The locking/unlocking issue could be related to a faulty sensor or software bug, which might require a dealer diagnostic check.

Given that you had Lexus Roadside Assistance and the service department guiding the jump-start, it’s frustrating that the dealership is still holding you responsible. You might want to escalate the issue with Lexus corporate or check if there are any recalls or service bulletins related to battery problems for your model.

I hope you get some resolution soon—this is definitely not the experience you should be having with a new car.