Same story here, our new 450h+ has already left us stranded. Installed a 12v battery monitor and have watched it slowly lose charge every day until critically low necessitating an overnight trickle charge. We drive it daily and 2 hours a day two of the days a week. On our most recent longer trip, the battery went from 12.5v before to 12.3v afterward.

Has anyone taken their car in for resolution of this? I feel a simple battery swap will not be the solution as there appears to be a parasitic draw and insufficient charging happening. I’ve disabled the digital key with no change.

 

Its good to see confirmation that disabling the digital key did not resolve the problem. Although it could be the Connected Services and Bluetooth proximity sensors to the key fob causing the parasitic drains as well, in particular scenarios.

I had researched the longer-in-field reliability (2+ years) of the latest generation NX450h+ and NX350h field reliability before going for the RX450h+ - and the NX's have the exact same battery problem. So its systemic - but worsened by at least a few factory-defect batteries.

In the linked thread - at least a couple folks reported that replacing with a "bigger battery" fixed their problem. I take that to mean, ones with more reserve capacity. Here in the RX forums, WellsB narrowed down to a Odyssey battery that would fit the bill, literally by fitting into the stock battery's space. However, I don't know if any RX owner actually replaced their stock battery with an Odyssey to find their problems go away. If someone's willing to try, that'd be great (of course, it would be out of pocket cost vs. dealer replacing under warranty) - assuming the dealer-replaced batteries leave the problem open.

 

Great idea to replace the OEM Lexus battery with an Odyssey AGM battery. I’m thinking you could even go up one size to the Odyssey ODP-AGM48 H6 L3. This has the same height and width as the H5 L2 you cite, but is 1.5” longer. The battery tray in the RX450h+ looks like it would accommodate this longer battery. This would give you an increased capacity of 70 Ah, versus the 60 Ah of the OEM battery. Plus the advantages of being an AGM versus the OEM FLA battery. Do you think this would work? Do you need to adjust anything in the charging circuit to accommodate an AGM battery?

 

Seconding these questions to figure amongs us here.

Last night, there was a freeze alert in Northern California and temperatures dipped to, well, just 4 C. I was going out to the stores at 10 am or so, and found my 450h+ bricked by a dead 12 V battery - yes, finally joining this inglorius "dead-battery club". Thanks to this forum, I was prepared with my mere 44 Wh battery from my vacuum-***-jumpstarter, which I bought for ~ $50 and now can be had for $ 25 apparently, paid off. I guess the battery hadn't deep-discharged since this puny jump starting battery was enough to switch to ready-mode - although obviously there is no need for cold-cranking-amps. I kept the car running for about half hour with the ICE on - and then headed out to the store - perhaps about an hour of running the ICE that apparently reasonably charged the 12 V back up to health. The car runs fine now. I might however keep the electric charging on overnight tonight (also a cold night), just to ensure that the 12 V is not discharged again - because WellB and others found that keeping the charging on at least "floats" the 12 V voltage - although probably not charging it, going by the latest posts. Call my PHEV charging the poor man's trickle-charger - I would like to avoid hooking up a trickle charger to a $ 70K+ supposedly ultra-reliable Lexus For what its worth, while I was driving the car fine for 30 mile commutes over the last few days, I seem to have noticed that the rear-doors were not opening with touch to the handle - but using the key fob worked to open the car. Hadn't thought much about it - but now thinking if that were early signs of low-voltage output.

This is a really sad and shameful situation - to be honest - to have to go through this. I saved Lexus $$ by not calling "road-side assistance" to my home garage, and saved myself time and effort today - I would ideally have liked Lexus to replace the stock/OEM battery with the Odyssey being discussed. Of course, that's not happening - so it'd be great if more knowledgeable folks like WellsB can confirm their best guess of the "largest" reserve capacity battery we can put in - without affecting Lexus warranty - so that I can prepare for next winter.

 

@SMartin
what Amazon battery monitor did you purchase, sounds like a great tool . Also, how did you specifically monitor the fuse voltage, what fuse extender did you use for that.

Thanks

 

I must concur with those of you that favor moving up to an Odyssey AGM battery, either a Group 47 (H5) or a Group 48 (H6). It seems that the most critical dimension is the height, at 7.5 inches, as it really cannot be any higher than that. The plastic battery compartment cover rests right on top of the two poles and any taller would cause a bulge and possibly an issue. Width is also critical, due to the battery bracket/strap that goes over the top. The length just may have some wiggle room in there on the RX450h+. I checked the battery area on my wife's NX450h+ and the length appears to be a bit more cramped in that area. On that model the battery is on the driver's side of the cargo area and it is mounted 90 degrees differently than in the RX model so, I'm thinking that only the Group 47 (H5) might fit. I just did a trickle charge on both cars last night, as I did not want go thru the dead battery crap again. I am using this voltage meter in each of my PHEV's to monitor the juice going to the 12v batteries. It only provides a reading while in the READY mode but, I have another one in the cargo area which is hard wired to the battery in order to provide a reading on battery juice when the engine is off. The LED can be turned on and off in order to not have a parasitic drain. Sorry to learn of your misfortune, Wrinkle but, I'm glad that you got it worked out.

 

The downside to the Odyssey units is, obviously, the cost.....they ain't cheap. The upside is that they are not made in China, as are many of the others in the marketplace. There are similar Chinese AGM's for less than half the cost of the Odyssey units. If Odyssey's cost twice the price, are they going to last twice as long? If so, I might go for one (or two, in my case). I see mostly favorable reviews on the Odyssey but, there are a few disgruntled buyers out there, as well. I've seen some people that tried to get warranty service on an item purchased thru Amazon and were refused, as it wasn't purchased directly or thru an authorized dealer network. (not speaking of batteries in this instance). In any event, I am still kicking this idea around.

 

Lexicon1, I used this battery monitor from Amazon:


It has a nice App for the iPhone that lets you download data when you get close to the vehicle (within about 15’ in my case). It will also send you alerts when the battery voltage drops too low so you can put a trickle charger on your battery or run the vehicle to recharge.





I monitored the fuse voltage and current two ways:
(1) You can put multimeter probes on the two contact points (indents) on the back of the fuse. If there’s any current flow, the resistance of the fuse will give you a few millivolts across the fuse. You can find tabulated values of fuse resistance for each fuse value; by dividing your measured voltage by this resistance, you get the current. (2) I altered an add-a-circuit fuse tap adapter that replaces a fuse and lets you bring the current out. I added a 0.5 Ohm resistor and a return wire to bring current back into the fuse plug point. (You could just use an Ammeter to measure the current, but my multimeter doesn’t work on current measurement.). By measuring the voltage across the 0.5 Ohm resistor, you can get the current flow through the fuse. I’ll try to add a photo.

 

I actually don’t see a reason to use an AGM battery in the hybrids. Lead acid batteries should last a minimum of 8 years being in the back of the car. The RX350 could benefit with one since the battery is close to the turbo and AGM handles the heat better.

 

Now having posted about my dead-battery club membership in the general 5th RX forum (as it doesn't have to do with the hybrid drive-train, just the 12 battery) - I figured checking about the 12 V charging here specific to the 450H+ :

Is it now confirmed that the PHEV charging hours don't actually charge the 12 V battery ?

Is the 12 V battery then at least not discharged by parasitic drain with the traction battery charging ?

The parasitic drain causes is still quite a mystery under investigation - but I have now started to switch off my lone keyfob until the night temperatures are higher. I now have 2 consecutive nights of dead battery which I have tried to fix by driving around for more than an hour today.

Additionally, these are some of the reports from the NX450H+ members about members exploring AGM/Odyssey batteries. The Youtube video posted that the computer needs to be updated to "register" a new battery for its charging algorithms. I'm therefore wondering, for the PHEV, with even more complex electronics - is it best to get a dealer make the switch to an AGM battery - so that they take care of all these intricacies ? Being new to Lexus, I myself don't know an independent mechanic that I can trust with a 450H+ with regards to full knowledgebase of how to switch to an AGM.

 

I have owned many cars in my life so far. None of them have ever had any of the battery issues that you all are describing. My last car was a 2021 Honda CRV "Hybrid". When you spend 50-80K on a car that is in some cases is brand new, you shouldn't have to monitor you battery function, trickle charge your battery, upgrade to a larger battery at your cost. Lexus/Toyota are suppose to be the "cream of the crop" for producing reliable hybrids. I don't hear about battery issues like these from other manufacturers, Kia, Honda, Mercedes, BMW, Hyundai etc. all of whom make hybrids. I have not had any issues with my battery but my climate in VA is not as cold as up north. I wonder how wide spread this battery issue is across all of Toyota/Lexus production. Lexus/Toyota needs to figure this out!

 

It could just be a bad batch of batteries. The 2016 Golf R had this issue with the second batch that were shipped to the US. All of them had the batteries fail at 2 years plus or minus a month.

 

This is more about an "under-designed" reserve capacity of stock battery - which has far too much parasitic drain due to the monitoring/sensing electronics in the car's quiescent state (parked, locked) than its designed to handle, and high sensitivity to low temperature causing voltage drops - as the reasons to consider an AGM having a much greater reserve capacity than the Lexus' stock ones. So its not about having unexpected battery failures, but to get around "expected" battery deaths due to the parasitic drains and cold temperature sensitivity of the stock batteries. The NX hybrid forums have lots of threads about these. And now the RX hybrids and direct measurements too.

There have now been reports of these problems right after the first week of delivery, to a couple months, and in my case at ~4 months age of the car.

 

I am in FL right now and outside temps can hit all the way down to upper 50s F (13-15 C), and I have yet to see a dead 12V in my RX450h+

Granted, the car is in the garage so it might not actually hit that low inside there.

I have my Drive Pulse turned off, but have switched on the digital key again.

Also, I remember in my HEV Prius, there is no need to actually drive the car around to charge the 12V. I used to charge it by simply letting the Prius run in the driveway, as the hybrid battery will power up the 12V. I assume the PHEV will do the same.

 

My experience suggests that it needs single digit temperatures (4 C in my case) for the problem to show up. So definitely a problem even in California winters.

I did some measurements with my multimeter connected to the jumpstart-connection points of the battery in the hood today, and found that while keeping the car in "Ready" mode does provide charging voltages (13.5 V and above, I think I noticed) to the 12 V battery - I can confirm that charging the PHEV with a Level 2 charger does NOT actually charge the 12 V battery. In fact, switching on the Level 2 charging switched the car off from Ready mode that I kept it in, and thereby essentially force-switched off the 12 V charging - and the 12 V battery voltage dropped to 12.4-12.5 volts. This 12.4 - 12.5 V was still higher than the fully switched off car's voltage (i.e. powered off, locked and non-level2-charging state) of the 12 V battery that was at about 12.1-12.2 volts at 15 C when I checked today. This last fact suggests that the 12 V battery is "floated" and may not be susceptible to parasitic drain with the Level 2 charger connected - so I plan to Level 2 charge at 6 Amps tonight to prevent encountering another successive night of 12 V battery death.

The other annoying thing I noticed when dead battery happens and after I jump start is: The "panic" mode sets with flashers and horn until I hit the panic button of the keyfob. And the settings of the PHEV charger, such as my set max current setting of 16 A and off state of Auto lock/unlock of the charger are lost - although the seat settings are retained and many other settings are also retained.