Did my homework and verified DC to DC converter part # G9270-40010 that fits my 2024 RX350h also fits various Rav 4s. I did not find a correlation of this part # fitting any Prius from 2020 forward. Although many say there are different charging algorithms/logic programed for the shared converter, I did not find any Toyota technical service bulletins supporting this, which would be expected. I did find Software Update 25LC03 - EV Charging Performance & Display Software Update Certain 2023 RZ450e regarding "improving DC charging performance". Perhaps with your more advanced skill set you could take a look and see if this an algorithm update for the 12v charging and/or could this extend to other 5th gen systems.

 

25LC03 is an update for the BEV RZ450e. It's related to the traction battery, not the 12v battery. Unlike the RX450h+, the RZ450e can utilize DC fast chargers to charge its traction battery.

 

I appreciate your sleuthing with me, @Lexuscome , and you have independently replicated my far as my finding went in terms of hard facts and data - thanks for that, and not just blowing me off. That's where the facts and data trail ends. Thereafter, hearsay ("people saying different charging algorithms") begins, which are just people's speculation, if that. No one can know that because algorithms are black-box IP to the outside world - you can't ever prove differences to the outside world anything about algorithm, unless there is a recall/service bulletin that explicitly notes "firmware/update update to AC charging module", or some such thing - which never happened for the 4th Gen Hybrid System.

The one thing you can however tell is the how sparsely the 12 V gets charged over time - for both NX-h and RX-h hybrids. People over in the NX forums have made similar measurements and found the same exact sparse charging and 12 V battery coma/failures/deaths - establishing equivalence in both NX-h and RX-h hybrids. The earliest/frequent problems are also in the NX-PHEV/RX-PHEV, which can make sense since these are the most loaded in terms of sensors/electronic-frills, and therefore 12 V drain - because of these are the most expensive trims. The problem also exists in the outgoing generation of the Rav4 Primes, but not with as much severity/frequency as in the Lexi NX-h and RX-h. This fact suggested to me, that both and hardware and firmware/algorithm design is the same between Prime, NX-H and RX-H for 4th Gen Hybrid Systems - and the electrical loading made it progressively worse in those specific car models that have a higher loading due to greater number sensors and electrical frills such as "illuminated door sills".

Thereafter, I shared the YT videos of Dr. Weber's tutorial on the 4th Gen Hybrid System AND the 12-V charging subsystem in this thread - where he explicitly shows how the 12 V charging is well-integrated into the Hybrid System design. One has to carefully view and understand the teachings from Dr. Weber in the video, along with the measurements he makes to prove his points - to appreciate this, as I'm sure you did - but I suspect very few else bothered to. This to me suggested that the algorithm is part of the entire Hybrid System design, and Toyota/Lexus developed/designed the Hybrid System as a single/shared one-block - given how much Toyota/Lexus reduces development cost by doing designs this way, managing the supply-chain AND development cost/complexity to be the lowest possible.

Since I understand the business processes of developing complex systems, all of the above facts led me to formulate my hypothesis - which fits all of the empirically available data and evidence. Appreciate your joining me on that.

However, anyone here is free to formulate their own hypothesis (leading to plucking off their voltage sensor or any other part off their car!). I will no further comment on this matter, since its not worth my time/patience, to be honest.

 

Thanks. It made me wonder. If they used a simple USB memory stick (coded update) connected to the console port (RZ450e) to alter ECU performance for the traction battery, is there reason to believe they could produce an ECU update to improve the 12v battery charging algorithm? Surely it's possible vs. would they spend time & money for the fix?

 

Thanks again. Is there any evidence to suggest Toyota/Lexus could (vs. would of course) develop and deploy a ECU code update to increase the charging parameters for the 5th Gens affected?

 

I don't know about the "could" part, that-is, where the algorithm is processed and if those parameters could be easily changed or not.

As for the "would" part, I feel that if they wanted to, they would, either with another part update or a flash update, if possible. Toyota has never been shy about quietly updating parts and firmware in the past. Continous improvement is part of the brand, after all.

I am almost certain the algorithm has something to do with fuel / energy efficiency. The fact that the part and, I believe, the algorithm are shared between multiple Toyota and Lexus vehicles has me certain that it's not due to a limitation specific to the RX.

The fact that the part was updated previously leads me to believe that it is functioning as designed and that Lexus / Toyota has accepted the increased battery failure rate.as an acceptable cost. Maybe that calculus will change in the future, but I'm not hopeful at this point.

 

This video talks about several hidden modes that can put your car into a deeper sleep to save the battery when parked for long periods. It also has other interesting settings.

 

Anybody verified these settings yet?

 

After reading all the comments above, I am worries about the 12v battery now. I have a 2025 RX 350H for one year. I brought my car to install the dashcam last week. I noticed the installer was using the ACC model to test out the fuse and the dashcam while the headlight is in auto.

I live in a condo, so I am not able to charge the battery myself since there is no power plug nearby. Is there another way to charge up the battery for my situation? I bought a self jump start kit and it is stored in the trunk. Maybe it is not a good idea to store in the trunk. Where do you guys store the jump starter kit? I am looking for some aftermarket storage under the seat to store the jump starter kit but I couldn’t find any.

 

We store our booster/jumper battery under the passenger front seat.

 

I highly recommend a Bluetooth battery monitor so you aren't in the blind about your battery resting voltage.


The battery charges when the hybrid system is on (Ready Mode) and in park. Worst case, you can do that for an hour or so to bump up the state of charge.

If you get enough sun,, either at home or work, a solar charger is an option.

 

I store my Ionic Emergency Battery Booster attached to the 12 volt battery. It can be activated by a Bluetooth app on my iPhone from inside or outside the car, or by pressing a button on the unit if I didn't have my phone with me.

 

I am not familiar with the Bluetooth monitor. Do you have a link? Does the 12v battery charge only in ready mode or park? What about driving?

 

https://a.co/d/02u5eyab

The battery is always charging (>14v) when in Ready mode and in Park. When driving, the battery is usually only maintained at around 12.8v, not actually charged

 

That's sounds like a smart idea. Have you tried the jump start yet? Do you mind to take a picture of your setup? How do you secure the booster on top of the battery? I assume you cannot close the lid after you put the booster on the battery. Thanks.