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While we haven't seen any battery issues (500h driven every 3 - 4 days, often only 4 miles per trip) I would think that Lexus should be capable of finding a parasitic drain source ...although replacing a battery after a deep discharge is sometimes Good Practice.
Here is a video showing how to determine current draw. I can understand how it would take days for a shop to verify and follow-up on whether a certain module is a source of this issue.
Car owners under warranty should not be expected to do these types of things, themselves, I understand...
I’ve been on a campaign to preserve battery charge, i.e., minimize current flow when the vehicle is turned off. I had over 300 mA (0.3 A) of “dark current” before doing anything; that was draining the battery every couple of days. The following steps helped:
1. Turn off the Digital Key system on the vehicle (this was the biggie—most of the current draw in my case):
Settings -> Info & Security -> Enable digital keys -> OFF
2. Have the radio, display, etc. turn off immediately when the car is turned off:
Settings -> Vehicle customize -> Utility -> ACC customize -> ON
3. Have the lights turn off ASAP when vehicle turns off:
Settings -> Vehicle customize -> Lights -> Exterior lights: Auto off timer -> 7.5 seconds
Settings -> Vehicle customize -> Lights -> Interior lights: Auto off timer -> 7.5 seconds
4. Turn off all Push notifications in the Lexus App. This is what sends messages to your phone that something is in your back seat, doors are unlocked, etc.
5. Turning off the dome light above rear-view mirror (ok, this is excessive!)
Doing these things reduced my parasitic current to 28 mA (0.028 A) as measured by the Lexus dealer; they said this was the low end of the “dark current” spec and should be fine. And yet, with our normal driving (30 - 45 minutes per day) we could not keep the battery charged (see first figure below). My battery monitor said I was between 0 and 30% charged every day.
Then the dealer tested the battery and said it was shot (at only 6 months old). I think the constant draining of the battery (mainly by the Digital Key Bluetooth receiver cycling on/off constantly) damaged the battery so it would not take a charge, even if the vehicle was run for an hour. The dealer replaced the battery with another flooded lead-acid battery and it is doing much better at taking a charge and holding it (see second figure below). My battery monitor says I’m holding at between 70 - 95% charge with the same amount of daily driving.
This was a reminder to me that while it’s important to minimize parasitic current, that may not be enough. You also need a good battery that can take a charge! I tried to get the dealer to put in a larger battery (LN3/H6 vs. LN2/H5), but they said they can only put in the OEM size (LN2/H5) specified by Lexus. In the future, I plan to try an Odyssey H6 size with 70 A-h of capacity (vs. OEM 60 A-h). I’m also planning to put in a plug/wire to trickle charge from the outside. Figure below—any comments are appreciated. Note that there should also be a fuse in this circuit (not shown).
With original battery (6 months old) the battery voltage remains near 12.0 V (nearly fully discharged) when vehicle off. With new battery the battery voltage remains near 12.6 V (nearly fully charged) when vehicle off. Proposed bracket to mount panel-mount SAE connector underneath tow hitch. Trickle charger can be plugged into this to charge battery. There should be a fuse in the line connecting to + battery terminal (not shown).
Last edited by SMartin; 04-10-24 at 09:05 AM.
Reason: Forgot to mention something.
As a follow-up to my previous post regarding my RX450h+ 12v battery. I have installed the same battery monitor as SMartin's, on both of my PHEV's. Yesterday, when I parked the RX yesterday, in the late afternoon, the monitor read 97% resting charge level. This morning when i checked it with the app, it read 80%.
As a follow-up to my previous post regarding my RX450h+ 12v battery. I have installed the same battery monitor as SMartin's, on both of my PHEV's. Yesterday, when I parked the RX in the late afternoon, the monitor read 97% resting charge level. This morning when i checked it with the app, it read 80%.
What monitor did you use and remember if that is hooked up all the time it also draws amps if it bypasses aux or ready mode. Best way to see what kind of draw there is putting your meter in series with the battery. Put scale on 20A first for initial surge then on MA setting and this will show actual draw from all sources. On my ES it would jump from 75 to over 200ma at times as I am sure it was transmitting looking for fob or contacting Lexus. From this at home test it will give you a good indication of what is going on. Wish there was a switch to turn off the DCM module.
I’ve been on a campaign to preserve battery charge, i.e., minimize current flow when the vehicle is turned off. I had over 300 mA (0.3 A) of “dark current” before doing anything; that was draining the battery every couple of days. The following steps helped:
1. Turn off the Digital Key system on the vehicle (this was the biggie—most of the current draw in my case):
Settings -> Info & Security -> Enable digital keys -> OFF
2. Have the radio, display, etc. turn off immediately when the car is turned off:
Settings -> Vehicle customize -> Utility -> ACC customize -> ON
3. Have the lights turn off ASAP when vehicle turns off:
Settings -> Vehicle customize -> Lights -> Exterior lights: Auto off timer -> 7.5 seconds
Settings -> Vehicle customize -> Lights -> Interior lights: Auto off timer -> 7.5 seconds
4. Turn off all Push notifications in the Lexus App. This is what sends messages to your phone that something is in your back seat, doors are unlocked, etc.
5. Turning off the dome light above rear-view mirror (ok, this is excessive!)
Doing these things reduced my parasitic current to 28 mA (0.028 A) as measured by the Lexus dealer; they said this was the low end of the “dark current” spec and should be fine. And yet, with our normal driving (30 - 45 minutes per day) we could not keep the battery charged (see first figure below). My battery monitor said I was between 0 and 30% charged every day.
Then the dealer tested the battery and said it was shot (at only 6 months old). I think the constant draining of the battery (mainly by the Digital Key Bluetooth receiver cycling on/off constantly) damaged the battery so it would not take a charge, even if the vehicle was run for an hour. The dealer replaced the battery with another flooded lead-acid battery and it is doing much better at taking a charge and holding it (see second figure below). My battery monitor says I’m holding at between 70 - 95% charge with the same amount of daily driving.
This was a reminder to me that while it’s important to minimize parasitic current, that may not be enough. You also need a good battery that can take a charge! I tried to get the dealer to put in a larger battery (LN3/H6 vs. LN2/H5), but they said they can only put in the OEM size (LN2/H5) specified by Lexus. In the future, I plan to try an Odyssey H6 size with 70 A-h of capacity (vs. OEM 60 A-h). I’m also planning to put in a plug/wire to trickle charge from the outside. Figure below—any comments are appreciated. Note that there should also be a fuse in this circuit (not shown).
With original battery (6 months old) the battery voltage remains near 12.0 V (nearly fully discharged) when vehicle off. With new battery the battery voltage remains near 12.6 V (nearly fully charged) when vehicle off. Proposed bracket to mount panel-mount SAE connector underneath tow hitch. Trickle charger can be plugged into this to charge battery. There should be a fuse in the line connecting to + battery terminal (not shown).
I appreciate your efforts in this ongoing issue. I am certain that the H5 (Grp47) battery will fit fine but, the H6 (Grp48) may very will fit also. It appears that it will in the RX450h+ but, I am not so certain that it will fit in my other car, the NX450h+. It looks to be a tight squeeze in that one.
What monitor did you use and remember if that is hooked up all the time it also draws amps if it bypasses aux or ready mode. Best way to see what kind of draw there is putting your meter in series with the battery. Put scale on 20A first for initial surge then on MA setting and this will show actual draw from all sources. On my ES it would jump from 75 to over 200ma at times as I am sure it was transmitting looking for fob or contacting Lexus. From this at home test it will give you a good indication of what is going on. Wish there was a switch to turn off the DCM module.
As a follow-up to my previous post regarding my RX450h+ 12v battery. I have installed the same battery monitor as SMartin's, on both of my PHEV's. Yesterday, when I parked the RX yesterday, in the late afternoon, the monitor read 97% resting charge level. This morning when i checked it with the app, it read 80%.
I have been measuring with my multimeter under the hood - and finding resting voltages of 12.05 V (with keyfob in pocket while measuring). This is consistent with what WellsB reported on direct voltage measurements of his 450H+. And what Smartin recorded/plotted as voltage data in the RX350h forum thread, for his older battery that dealer then certified as “shot” and then replaced it. I think its also directly correlated with the % charge numbers - if we use WellB’s quoted table of % SOC and voltage. So the data is all lining up between you, WellsB, SMartin and myself, I think - correct me if anyone sees any discrepancies.
What that would imply - assuming SMartin’s dealer assesment is the way to go - Stefanos’, mine and WellsB’s batteries are likely all shot and need replacement - given these resting voltages. The trickle chargers are really providing end-of-life support - and Im not even using one, so at risk of another battery death anytime.
I have not used the digital key in a while. When I look in the Lexus app it gives the option to Download the Digital Key. When I go to the car Info & Security settings there is no option to set digital key to off. Can I assume the digital key was somehow deleted and therefore it's parasitic drain would not be an issue on my vehicle?
I’ve been on a campaign to preserve battery charge, i.e., minimize current flow when the vehicle is turned off. I had over 300 mA (0.3 A) of “dark current” before doing anything; that was draining the battery every couple of days. The following steps helped:
1. Turn off the Digital Key system on the vehicle (this was the biggie—most of the current draw in my case):
Settings -> Info & Security -> Enable digital keys -> OFF
2. Have the radio, display, etc. turn off immediately when the car is turned off:
Settings -> Vehicle customize -> Utility -> ACC customize -> ON
3. Have the lights turn off ASAP when vehicle turns off:
Settings -> Vehicle customize -> Lights -> Exterior lights: Auto off timer -> 7.5 seconds
Settings -> Vehicle customize -> Lights -> Interior lights: Auto off timer -> 7.5 seconds
4. Turn off all Push notifications in the Lexus App. This is what sends messages to your phone that something is in your back seat, doors are unlocked, etc.
5. Turning off the dome light above rear-view mirror (ok, this is excessive!)
Doing these things reduced my parasitic current to 28 mA (0.028 A) as measured by the Lexus dealer; they said this was the low end of the “dark current” spec and should be fine. And yet, with our normal driving (30 - 45 minutes per day) we could not keep the battery charged (see first figure below). My battery monitor said I was between 0 and 30% charged every day.
Then the dealer tested the battery and said it was shot (at only 6 months old). I think the constant draining of the battery (mainly by the Digital Key Bluetooth receiver cycling on/off constantly) damaged the battery so it would not take a charge, even if the vehicle was run for an hour. The dealer replaced the battery with another flooded lead-acid battery and it is doing much better at taking a charge and holding it (see second figure below). My battery monitor says I’m holding at between 70 - 95% charge with the same amount of daily driving.
This was a reminder to me that while it’s important to minimize parasitic current, that may not be enough. You also need a good battery that can take a charge! I tried to get the dealer to put in a larger battery (LN3/H6 vs. LN2/H5), but they said they can only put in the OEM size (LN2/H5) specified by Lexus. In the future, I plan to try an Odyssey H6 size with 70 A-h of capacity (vs. OEM 60 A-h). I’m also planning to put in a plug/wire to trickle charge from the outside. Figure below—any comments are appreciated. Note that there should also be a fuse in this circuit (not shown).
With original battery (6 months old) the battery voltage remains near 12.0 V (nearly fully discharged) when vehicle off. With new battery the battery voltage remains near 12.6 V (nearly fully charged) when vehicle off. Proposed bracket to mount panel-mount SAE connector underneath tow hitch. Trickle charger can be plugged into this to charge battery. There should be a fuse in the line connecting to + battery terminal (not shown).
Good info!
4. Turn off all Push notifications in the Lexus App. This is what sends messages to your phone that something is in your back seat, doors are unlocked, etc.
This would be in the app...
Click on profile pic on top right hand side of app --> Go to ACCOUNT --> NOTIFICATION SETTINGS
I was dreading when I saw this thread but alas... I have to add "me too" have this issue.
I picked up my 2024 RX450h+ March 30th, Feb 2024 build. I've put in 508 miles, last time I drove it was last Saturday and when I tried to unlock earlier today it was dead. I have one of those battery booster pack that I specifically bought for my daily driver (Ioniq 5 which I've had for 2 years now and never needed it). Tried to jump via engine bay jump points, didn't work, had to crawl and manually open the tailgate and connect the booster to the battery terminals, worked as soon as I plugged as the alarm went off. Drove it for about 30 miles. Let's see how long it lasts.
I'm coming from a 2021 BMW X5 45E (PHEV) which was truly a garage queen. 3 years and have driven less than 10k miles, never had any battery issue even after not using it for more than a month. I didn't want to keep it as I know repairs in the future would be really expensive. Slightly annoyed as I thought moving on to Lexus it would be problem free etc.
I was dreading when I saw this thread but alas... I have to add "me too" have this issue.
I picked up my 2024 RX450h+ March 30th, Feb 2024 build. I've put in 508 miles, last time I drove it was last Saturday and when I tried to unlock earlier today it was dead. I have one of those battery booster pack that I specifically bought for my daily driver (Ioniq 5 which I've had for 2 years now and never needed it). Tried to jump via engine bay jump points, didn't work, had to crawl and manually open the tailgate and connect the booster to the battery terminals, worked as soon as I plugged as the alarm went off. Drove it for about 30 miles. Let's see how long it lasts.
I'm coming from a 2021 BMW X5 45E (PHEV) which was truly a garage queen. 3 years and have driven less than 10k miles, never had any battery issue even after not using it for more than a month. I didn't want to keep it as I know repairs in the future would be really expensive. Slightly annoyed as I thought moving on to Lexus it would be problem free etc.
You really need to put it on a charger until it is fully charged or you will probably be facing the same issue soon, and will certainly be greatly shortening the lifespan of the battery if you don't. It will take about 8 hours to charge with an 8 amp charger, and about 30 hours with a 2 amp charger. The vehicle charging system will never fully charge it.
I would not assume that a battery is bad based on its resting voltage in the vehicle. A battery needs to be tested to determine if it is bad.
I've found that having the key fob near the vehicle pulls the voltage down, meaning that one is no longer measuring resting voltage. Considering that the vehicle reports a hood-open condition to the app, I would not be surprised if that pulls the voltage down too.
I've not tested my battery lately, though I intend to after the next charging cycle, but I know that it takes an appropriate time to recharge it, so it is probably still good from a capacity standpoint. I did test the battery when new, so I have a baseline. I use an Argus Engineering professional tester, which is no longer available for purchase.
I had been following this thread for a while because I was in the market for a RX PHEV. However, given the dead battery issue many users are reporting, I have decided to wait until Lexus gets a chance to sort this out.
I own a 2022 (4th gen) RX 450h with 16k miles. We just came back from a 12-day trip and the RX started without any fuss. So this dead battery issue is definitely a regression for 5th gen RX.
I want to share a different perspective. My other car is a BEV (Genesis G80). G80 also has a lot of electronics like RX (including digital key), but I never faced any dead battery issue. In G80, the 12 V battery is charged when the car is plugged in and when the car is in READY state. In addition, the car actively monitors the status of 12 V battery. If the charging level drops below a threshold, the traction battery charges the 12 V battery even when the car is parked. It seems to me this particular charging logic is missing in RX.
Attached: relevant pages from G80 instruction manual.
I would not assume that a battery is bad based on its resting voltage in the vehicle. A battery needs to be tested to determine if it is bad.
I've found that having the key fob near the vehicle pulls the voltage down, meaning that one is no longer measuring resting voltage. Considering that the vehicle reports a hood-open condition to the app, I would not be surprised if that pulls the voltage down too.
I've not tested my battery lately, though I intend to after the next charging cycle, but I know that it takes an appropriate time to recharge it, so it is probably still good from a capacity standpoint. I did test the battery when new, so I have a baseline. I use an Argus Engineering professional tester, which is no longer available for purchase.
Ok, good to know that our batteries are not definitively bad (yet) - I don't have the time to take it to the dealer, so will delay the dealer's battery check/replacement until the 5K miles / 6 month service, if I don't absolutely have to do something about it now.
I finally caved in and ordered a battery charger/maintainer - after having serious reservations of having to do this with a $70K+ premium luxury purportedly "ultra-reliable" Lexus. Its one thing if one does use a charger/maintainer to get battery life of 10 years, and quite another if one is forced to do this to just go about using a regularly used car that runs at least 3 times a week, logging about 100 miles of usage per week. Having signed up for only one (plugin) charger cable, I feel cheated by Lexus, given all this brouhaha about Toyota/Lexus reliability, since charging the 12 V battery adequately is not a complex item to design.
Please let us know what your 2nd battery test results are, WellsB - appreciate all your inputs.
I’ve been on a campaign to preserve battery charge, i.e., minimize current flow when the vehicle is turned off. I had over 300 mA (0.3 A) of “dark current” before doing anything; that was draining the battery every couple of days. The following steps helped:
4. Turn off all Push notifications in the Lexus App. This is what sends messages to your phone that something is in your back seat, doors are unlocked, etc.
Doing these things reduced my parasitic current to 28 mA (0.028 A) as measured by the Lexus dealer; they said this was the low end of the “dark current” spec and should be fine.
This is great to know - thanks for the investigations and sharing the results.
However, #4 above - I'm having a hard time understanding how #4 will help. Turning off all Push notifications in the Lexus app will turn off all Notifications from the Lexus servers or at least the querying of those notifications by the App/Phone. I figured the Car would send these notifications to the Lexus servers first (over the 4G connection) draining the battery - and then the Phone/App receive them from the servers. So to improve the quiescent battery drain of the car, I would think we should have a way to prevent the Car sending these notifications to the Lexus servers in the first place. Is there a way to do so you found ? Such as by turning off any or all of the "connected car" settings from within the car or in the app ? Did that help ?
FWIW, I have turned off the "Drive Pulse" feature from the App, so that the Car doesn't (have to) send the location and gyroscope information to the Lexus servers - which also serves the purpose of not sharing my data with potential databrokers Lexus may choose to sell them to.
04-10-24, 06:22 AM
...although replacing a battery after a deep discharge is sometimes Good Practice.
I have one of those battery booster pack that I specifically bought for my daily driver (Ioniq 5 which I've had for 2 years now and never needed it). Tried to jump via engine bay jump points, didn't work, had to crawl and manually open the tailgate and connect the booster to the battery terminals, worked as soon as I plugged as the alarm went off. Drove it for about 30 miles. Let's see how long it lasts.
