Dead 12v battery Incident (merged threads)
04-28-24, 11:21 AM
#316
Given how proactively careful you are with the 12 V battery, WellsB - if you are able to kill it, then I suspect 100 % of the 5th Gen RX 450H+ will eventually end up killing it one way or another 
Curiosity question: Did you happen to take any voltage readings at all during this episode, at the failed/degraded state - or when you started out with the battery minder perhaps ? I'm curious to know what exactly is the "dead" voltage of the 12 V battery, from the perspective of the 450H+ computer.
Its good to confirm that one can jump the car with 20 Amp current, as that matches what one would expect from a hybrid/PHEV without a starter motor.
At some point, given Lexus won't do anything since 2022 when the NX450H+ started having this problem - I'm really interested in learning if there is anything we can do along the lines of a larger reserve capacity battery than the stock/OEM one (paid out of pocket). AGM batteries seem to need a slightly larger (0.5 - 0.75 V) charging voltage than the usual flooded lead-acid that is the RX450H+ stock/OEM (and its replacement from dealers that one can get under warranty) - so it seems an AGM may not be drop-in replacement that actually reduces the probability of a dead battery to near zero in any reasonable situation. That said, Odyssey does advertise an AGM for a 2023 NX450H+ despite the potential larger charging voltage need - so I'm not sure if Odyssey somehow reduced the charging voltage need to match the Lexus OEM battery for NX450H+. Understood however that the real problem is the charging algorithm that only Lexus can fix.
I'm not set on an AGM though, and even a regular lead-acid that reduces the chances of a dead 12 V situation significantly would be necessary, longer term. Its just very annoying/problematic to have to deal with this "risk" constantly (even when carrying a jump starter) - especially if/when is traveling out to national parks and such remote locations whether may not be even a possibility of any trickle-charger.
Curiosity question: Did you happen to take any voltage readings at all during this episode, at the failed/degraded state - or when you started out with the battery minder perhaps ? I'm curious to know what exactly is the "dead" voltage of the 12 V battery, from the perspective of the 450H+ computer.
Its good to confirm that one can jump the car with 20 Amp current, as that matches what one would expect from a hybrid/PHEV without a starter motor.
At some point, given Lexus won't do anything since 2022 when the NX450H+ started having this problem - I'm really interested in learning if there is anything we can do along the lines of a larger reserve capacity battery than the stock/OEM one (paid out of pocket). AGM batteries seem to need a slightly larger (0.5 - 0.75 V) charging voltage than the usual flooded lead-acid that is the RX450H+ stock/OEM (and its replacement from dealers that one can get under warranty) - so it seems an AGM may not be drop-in replacement that actually reduces the probability of a dead battery to near zero in any reasonable situation. That said, Odyssey does advertise an AGM for a 2023 NX450H+ despite the potential larger charging voltage need - so I'm not sure if Odyssey somehow reduced the charging voltage need to match the Lexus OEM battery for NX450H+. Understood however that the real problem is the charging algorithm that only Lexus can fix.
I'm not set on an AGM though, and even a regular lead-acid that reduces the chances of a dead 12 V situation significantly would be necessary, longer term. Its just very annoying/problematic to have to deal with this "risk" constantly (even when carrying a jump starter) - especially if/when is traveling out to national parks and such remote locations whether may not be even a possibility of any trickle-charger.
In the meantime, we're all in the club of which nobody wants to be a member.
Last edited by StefanoS; 04-29-24 at 11:00 AM.
04-28-24, 08:37 PM
#317
Intermediate
IThe highest charging voltage that I have observed in both of my cars, while driving is 14.2V, which seems to be insufficient for charging an AGM. I have become a bit more proactive by using the battery monitors that I have in both vehicles. ..
In the meantime, we're all in the club of which nobody wants to be a member.
In the meantime, we're all in the club of which nobody wants to be a member.
Let's see if we can get some insights from the NX owners, now that we are in this inglorious club
The following users liked this post:
StefanoS (04-29-24)
04-29-24, 10:58 AM
#318
Since I bought into the Lexus club after reading about how little of a problem the 12 V battery is, after reading quite a few (and asking my questions) in related threads in the 2nd Gen NX hybrid forum (that has been in the field longer than the 5th Gen RX), I posted the question about their AGM or otherwise battery fix in this thread there.
Let's see if we can get some insights from the NX owners, now that we are in this inglorious club
Let's see if we can get some insights from the NX owners, now that we are in this inglorious club
The following users liked this post:
wrinkle (04-29-24)
04-29-24, 01:33 PM
#319
I took my RX in to get the gas fuel door replaced and asked them to check my battery as it has died twice, it failed the load test and was replaced under warranty. Cheers
The following users liked this post:
wrinkle (04-29-24)
04-29-24, 01:58 PM
#320
[QUOTE=alextv;11708263]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.[/QUOTE
Knock on wood, after the DCM replacement, there has been no issue. I still try to open a door every morning and pray it opens. So far so good. I think they did solved the mystery.
Knock on wood, after the DCM replacement, there has been no issue. I still try to open a door every morning and pray it opens. So far so good. I think they did solved the mystery.
The following users liked this post:
coolbrazz (04-30-24)
04-29-24, 06:40 PM
#321
10th Gear
Join Date: Apr 2024
Posts: 11
Likes: 0
Received 0 Likes
on
0 Posts
Lexus phev 12 volt mistake
LEXUS will ultimately have it's worst reputational experience as a result of not thinking through the experience and effect of have distance phev cars and NOT ADDRESS THE CHARGING OF THE OPERATIONAL 12 VOLT BATTERY SYSTEM THAT RUNS THE CAR (NOT THE WHEELS) There are battery failures and car lockups in great abundance ... A PARTICULAR PROBLEM FOR THOSE WHO BOUGHT INTO THAT CONCEPT FOR FULL TIME SHORT DISTANCE WORK OR PERSONAL TRAVEL ... THE 12 VOLT SYSTEM HAS NO REALISTIC CHARGING ALTERNATIVES AND FAILS.
04-29-24, 06:47 PM
#322
10th Gear
Join Date: Apr 2024
Posts: 11
Likes: 0
Received 0 Likes
on
0 Posts
I should add I was locked in my car with less than1000 miles when the operational 12v system failed ... The battery had to be replaced AFTER THE THE CAR WAS TOWED TO A DEALER ON MY ACCOUNT.
05-01-24, 09:18 PM
#323
05-02-24, 11:01 AM
#324
10th Gear
Join Date: Apr 2024
Posts: 11
Likes: 0
Received 0 Likes
on
0 Posts
i'd be interested in knowing the cause of the 12v failures.
I've owned a prius for 15 years now and not one single time has it ever gotten a discharged 12v battery...except when we forgot to turn off a light.
I use dr. Prius to check the voltage of the battery, so maybe i'll start monitoring it daily to see whether something is draining the thing. I mean, we do know the car has sensors all over (just going close to the car with the fob switches on the handle lights). It also is connected to the net, even while not started.
Ps. We sometimes go on week-long or more trips (e.g. Cruise or travel abroad). If this happens, it's good to know i can start the car remotely to charge the 12 v (at least until 2027, when i need to pay for it)
I've owned a prius for 15 years now and not one single time has it ever gotten a discharged 12v battery...except when we forgot to turn off a light.
I use dr. Prius to check the voltage of the battery, so maybe i'll start monitoring it daily to see whether something is draining the thing. I mean, we do know the car has sensors all over (just going close to the car with the fob switches on the handle lights). It also is connected to the net, even while not started.
Ps. We sometimes go on week-long or more trips (e.g. Cruise or travel abroad). If this happens, it's good to know i can start the car remotely to charge the 12 v (at least until 2027, when i need to pay for it)
05-02-24, 12:39 PM
#325
Instructor
The 12v aux battery is charged by the hybrid battery and braking or engine charge the hybrid battery. Software updates can correct how much the aux battery charges if they are working on it but I think it is a combination of charging and drain they are having to deal with. For my ES300h the aux battery is acting a lot better since the subscriptions ran out.
05-02-24, 05:01 PM
#326
10th Gear
Join Date: Apr 2024
Posts: 11
Likes: 0
Received 0 Likes
on
0 Posts
I assume that model is not one of the NEW PHEV - models that are designed to go 30 miles miles on the NEW BATTERY CONFIGURATION ... woe be unto to those WHO BOUGHT THAT FOR LOCAL COMMUTE USE COUNTING ON THE 30 MILE RANGE TO MAKE IT THEIR ELECTRIC CAR FOR COMMUTE PURPOSES ... THAT IS NOT HAPPENING ...AND WON'T UNTIL AND UNLESS THERE IS A PROGAM CHANGE REGARDING THE RELATIONSHIP BETWEEN THE BIG BATTERY SYSTEM AND THE 12V SYSTEM...RIGHT NOW THERE IS NO INTERCHANGE OF STORAGE OR CHARGE. THE QUICK FIX FOR ME WAS TO OBTAIN AND USE A SEPARATE CHARGER FOR THE 12V BATTERY IS IS A DIRECT HOOK UP AND AVAILABLE BY A WIRES ATTACHED DIRECTLY TO THAT BATTERY. ULTIMELY LEXUS HAS TO PROVIDE PROGRAM OR WIRING CHANGES THAT ALLOW THE 12V TO BE MAINTAIN BY POWER FROM THE PHEV BATTERY SYSTEM. I HAVE PROVIDED INFORMATION TO CONSUMERS REPORTS AND HOPE THEY HELP DRIVE THE NECESSSARY MODIFICATIONS.
models that are designed to go 30 miles miles on the NEW BATTERY CONFIGURATION ... woe be unto to those WHO BOUGHT THAT FOR LOCAL COMMUTE USE COUNTING ON THE 30 MILE RANGE TO MAKE IT THEIR ELECTRIC CAR FOR COMMUTE PURPOSES ... THAT IS NOT HAPPENING ...AND WON'T UNTIL AND UNLESS THERE IS A PROGAM CHANGE REGARDING THE RELATIONSHIP BETWEEN THE BIG BATTERY SYSTEM AND THE 12V SYSTEM...RIGHT NOW THERE IS NO INTERCHANGE OF STORAGE OR CHARGE. THE QUICK FIX FOR ME WAS TO OBTAIN AND USE A SEPARATE CHARGER FOR THE 12V BATTERY IS IS A DIRECT HOOK UP AND AVAILABLE BY A WIRES ATTACHED DIRECTLY TO THAT BATTERY. ULTIMELY LEXUS HAS TO PROVIDE PROGRAM OR WIRING CHANGES THAT ALLOW THE 12V TO BE MAINTAIN BY POWER FROM THE PHEV BATTERY SYSTEM. I HAVE PROVIDED INFORMATION TO CONSUMERS REPORTS AND HOPE THEY HELP DRIVE THE NECESSSARY MODIFICATIONS.
models that are designed to go 30 miles miles on the NEW BATTERY CONFIGURATION ... woe be unto to those WHO BOUGHT THAT FOR LOCAL COMMUTE USE COUNTING ON THE 30 MILE RANGE TO MAKE IT THEIR ELECTRIC CAR FOR COMMUTE PURPOSES ... THAT IS NOT HAPPENING ...AND WON'T UNTIL AND UNLESS THERE IS A PROGAM CHANGE REGARDING THE RELATIONSHIP BETWEEN THE BIG BATTERY SYSTEM AND THE 12V SYSTEM...RIGHT NOW THERE IS NO INTERCHANGE OF STORAGE OR CHARGE. THE QUICK FIX FOR ME WAS TO OBTAIN AND USE A SEPARATE CHARGER FOR THE 12V BATTERY IS IS A DIRECT HOOK UP AND AVAILABLE BY A WIRES ATTACHED DIRECTLY TO THAT BATTERY. ULTIMELY LEXUS HAS TO PROVIDE PROGRAM OR WIRING CHANGES THAT ALLOW THE 12V TO BE MAINTAIN BY POWER FROM THE PHEV BATTERY SYSTEM. I HAVE PROVIDED INFORMATION TO CONSUMERS REPORTS AND HOPE THEY HELP DRIVE THE NECESSSARY MODIFICATIONS.
models that are designed to go 30 miles miles on the NEW BATTERY CONFIGURATION ... woe be unto to those WHO BOUGHT THAT FOR LOCAL COMMUTE USE COUNTING ON THE 30 MILE RANGE TO MAKE IT THEIR ELECTRIC CAR FOR COMMUTE PURPOSES ... THAT IS NOT HAPPENING ...AND WON'T UNTIL AND UNLESS THERE IS A PROGAM CHANGE REGARDING THE RELATIONSHIP BETWEEN THE BIG BATTERY SYSTEM AND THE 12V SYSTEM...RIGHT NOW THERE IS NO INTERCHANGE OF STORAGE OR CHARGE. THE QUICK FIX FOR ME WAS TO OBTAIN AND USE A SEPARATE CHARGER FOR THE 12V BATTERY IS IS A DIRECT HOOK UP AND AVAILABLE BY A WIRES ATTACHED DIRECTLY TO THAT BATTERY. ULTIMELY LEXUS HAS TO PROVIDE PROGRAM OR WIRING CHANGES THAT ALLOW THE 12V TO BE MAINTAIN BY POWER FROM THE PHEV BATTERY SYSTEM. I HAVE PROVIDED INFORMATION TO CONSUMERS REPORTS AND HOPE THEY HELP DRIVE THE NECESSSARY MODIFICATIONS.
models that are designed to go 30 miles miles on the NEW BATTERY CONFIGURATION ... woe be unto to those WHO BOUGHT THAT FOR LOCAL COMMUTE USE COUNTING ON THE 30 MILE RANGE TO MAKE IT THEIR ELECTRIC CAR FOR COMMUTE PURPOSES ... THAT IS NOT HAPPENING ...AND WON'T UNTIL AND UNLESS THERE IS A PROGAM CHANGE REGARDING THE RELATIONSHIP BETWEEN THE BIG BATTERY SYSTEM AND THE 12V SYSTEM...RIGHT NOW THERE IS NO INTERCHANGE OF STORAGE OR CHARGE. THE QUICK FIX FOR ME WAS TO OBTAIN AND USE A SEPARATE CHARGER FOR THE 12V BATTERY IS IS A DIRECT HOOK UP AND AVAILABLE BY A WIRES ATTACHED DIRECTLY TO THAT BATTERY. ULTIMELY LEXUS HAS TO PROVIDE PROGRAM OR WIRING CHANGES THAT ALLOW THE 12V TO BE MAINTAIN BY POWER FROM THE PHEV BATTERY SYSTEM. I HAVE PROVIDED INFORMATION TO CONSUMERS REPORTS AND HOPE THEY HELP DRIVE THE NECESSSARY MODIFICATIONS.
Last edited by kitlz; 05-02-24 at 05:36 PM.
05-03-24, 04:36 PM
#327
I assume that model is not one of the NEW PHEV - models that are designed to go 30 miles miles on the NEW BATTERY CONFIGURATION ... woe be unto to those WHO BOUGHT THAT FOR LOCAL COMMUTE USE COUNTING ON THE 30 MILE RANGE TO MAKE IT THEIR ELECTRIC CAR FOR COMMUTE PURPOSES ... THAT IS NOT HAPPENING ...AND WON'T UNTIL AND UNLESS THERE IS A PROGAM CHANGE REGARDING THE RELATIONSHIP BETWEEN THE BIG BATTERY SYSTEM AND THE 12V SYSTEM...RIGHT NOW THERE IS NO INTERCHANGE OF STORAGE OR CHARGE. THE QUICK FIX FOR ME WAS TO OBTAIN AND USE A SEPARATE CHARGER FOR THE 12V BATTERY IS IS A DIRECT HOOK UP AND AVAILABLE BY A WIRES ATTACHED DIRECTLY TO THAT BATTERY. ULTIMELY LEXUS HAS TO PROVIDE PROGRAM OR WIRING CHANGES THAT ALLOW THE 12V TO BE MAINTAIN BY POWER FROM THE PHEV BATTERY SYSTEM. I HAVE PROVIDED INFORMATION TO CONSUMERS REPORTS AND HOPE THEY HELP DRIVE THE NECESSSARY MODIFICATIONS.
.
.
Mostly on EV every day or so (I can go 40+ miles on EV mode), and longer distances on HV...no complaints at all so far. Drives like a dream, and all the tech stuff just makes me drool.
If they do find something, then hopefully an OTA will fix it.
Also, I'm not sure since you seem to be screaming stuff, but you seem to think the hybrid battery does not push power to the 12V...that's completely wrong.
Last edited by asj2024; 05-03-24 at 05:03 PM.
05-04-24, 09:01 AM
#328
10th Gear
Join Date: Apr 2024
Posts: 11
Likes: 0
Received 0 Likes
on
0 Posts
hmmmm....CAPS....anyways, I've been using the car for more than 2 months now. No problems at all so far.
Mostly on EV every day or so (I can go 40+ miles on EV mode), and longer distances on HV...no complaints at all so far. Drives like a dream, and all the tech stuff just makes me drool.
If they do find something, then hopefully an OTA will fix it.
Also, I'm not sure since you seem to be screaming stuff, but you seem to think the hybrid battery does not push power to the 12V...that's completely wrong.
Mostly on EV every day or so (I can go 40+ miles on EV mode), and longer distances on HV...no complaints at all so far. Drives like a dream, and all the tech stuff just makes me drool.
If they do find something, then hopefully an OTA will fix it.
Also, I'm not sure since you seem to be screaming stuff, but you seem to think the hybrid battery does not push power to the 12V...that's completely wrong.
"Electric Car" mode it does not charge the 12v .. and it never goes to Hybrid mode.
05-04-24, 07:56 PM
#329
YOU did not understand ... I was NOT using the hybrid mode ... as I could use the electric mode on that battery solely for all my driving .. UNLESS I left town as I did this weekend... and in the
"Electric Car" mode it does not charge the 12v .. and it never goes to Hybrid mode.
"Electric Car" mode it does not charge the 12v .. and it never goes to Hybrid mode.
And you're still completely wrong when you say the 12V is charged solely by braking action.
Last edited by asj2024; 05-04-24 at 08:01 PM.
05-06-24, 06:41 AM
#330
Driver School Candidate
Glad to hear you’re up and running. I wonder if Lexus is going to at least give a discount on the trickle charger they sell. 😉
Last edited by Nitrous; 05-06-24 at 06:44 AM.