RBach

An update on the 12v battery parasitic draw for the new 2024 RX 450h+, where the vehicle 12v battery was 'dead' twice first week of ownership.

The local Lexus dealer has had the vehicle for ten days now, diagnosing and running tests. I'm told a (regional ?) Lexus engineer has visited the dealership during the process, providing guidance, probably asking questions. I don't have any real concrete answers, "aha" moments, or practical info on tests run, solutions found. What I am told - Thurs last week - is that they have observed the 12v battery (sitting in one of their garage bays this whole time) drop daily down to 11.8v. I'm being told this could be 'normal'. Doubt that, as my understanding is 11.8v on most 12v car batteries is a rather deep discharge.

I don't believe a brand-new $70k+ Lexus should have to have a trickle charger added daily to prevent a 'dead battery' situation with the vehicle, so yes: if this isn't resolved, we'll pursue the Lemon Law process.

alextv

In there tests can they tell amount of parasitic draw over a time period like 24 hrs? That would be smoothing out the ups and down of the draw and give an accurate total and that is what needs to be looked at to see if it is excessive. There entire lineup is facing similar problems just seems to be more severe in some like yours. For yours to be depleted within 1 week is not normal. If they think that is normal then a salesman when demonstrating a car on the lot would have to charge the battery just to test drive. As for the lemon law especially here in NC it is almost impossible to do but in other states I have heard all you have to do is hand the keys back over with no repercussion.

Urlik

Any lemon law buyback is done by Lexus and not the dealership. Lexus will tell you when and how to return the car they are buying back.

asj2024

So it's been sitting there for 10 days. It would be interesting to see whether they can restart it after 14 days...2 weeks. if so, then that seems like a typical modern car to me? Many sites suggest anything more than 14 days standing is iffy for 12V batteries, and that has always been my understanding too.

Urlik

It depends. VW and Audis go into a deep sleep with the car after 7 days to avoid this. Ford does it as well I believe.

pcm888usa

Mine 450h+ has been sitting in the dealership for 12 days. New battery did not do the trick. Today they declared they found the source of battery drain. It is a DCM that is bad. They replaced it. I have not gotten the car back yet but you may want to share this with your dealer. Since we are not the only unfortunate ones who had this kind of issue. My car is 1 month old. I am ready to turn it back to Lexus.

asj2024

It is defective in what way? Communication to network too much? Or something else? Thanks.

Imolared

I disagree, my previous 2021 X5 45E PHEV sat in the garage for weeks and sometimes over a month without being driven and never once I had to jump it. It had the same app and digital/proximity sensors/features as the RX450h+ (maybe even more, I love that I can unlock and drive that car just using my Apple Watch).

This is just **** poor battery management system that Lexus has.

wrinkle

I agree. Lexus is making me quite regret not even considering a BMW PHEV. Given how the latter's reputation for reliability has risen in the Consumer Reports reviews - in hindsight, I shouldn't have so ignored the NX450h+ sightings of this ridiculous 12 V battery management design in this forum, which I then considered something as only affecting folks in very cold climate. The primary non-negotiable reason I chose Lexus was reliability.

If a bigger sized battery or Lexus firmware update doesn't fix this, I may not choose to stay with Lexus long-term.

LeX2K

If this was my vehicle I'd something like this

wrinkle

It doesn't fix the problem - and wastes my money and time, as far as I'm concerned. So I'll pass being a "Lexus Champion"

RBach

Thank you very much for sharing what the dealer service dept told you, about changing a DCM. I truly hope that resolves it.

Yes, I sure will pass along that you had the same issue(s), and that is what they found. Fingers crossed this builds the Lexus engineering database, to create a quicker solution for those to come. Then on vehicles in production, changes the process to prevent from recurring for others.

Blessings

Rich

alextv

This gets back to the extensive tests that were done on your car. Find out from them what the cumulative parasitic draw that they measured and what does Lexus deem as normal draw. Not sure if you have done this but you can put an ammeter in series with the battery and see the spikes that happen quite often by the DCM transmitting. Just make sure your key is far away and put scale on 20A for initial spike and then reduce to ma scale. Mine jumps from 75 to around 200ma. If all seems to be in normal range then the battery is probably weak even if it checks ok but I think you have said the battery has already been changed. There will most likely be a software update to address the issue and no one knows they are working on the fix until it happens. Knowing what the draw was during there tests is important and not just the voltage drop.

CommodoreAmiga

I'd be curious to hear what the official threshold for vampire drain is from Lexus... But 75mA already sounds too high. I think other manufacturers specify upper limits around 50mA and actual drain is often much lower -- 10-15mA.

RPerez13

Did you have to purchase an extension cable to connect to the Neg Terminal in the hood (not back of car)?