12V battery problem

[Hayzee]

On 3/14/2024 at 2:30 PM, Simpson Iain said:

I have recently acquired a Lexus 2019 NX300h, and after reading posts on this forum on issues with the 12v battery, have started monitoring battery voltage with a digital multimeter. I have noticed that the voltage reduces the longer I do not drive the car. The lowest I have measured is 12.1v after not using the car for two days.

I checked my 12v Battery last week and it was showing 12.1v so I charged it and it went to 12.6v. a few days later and it showed 12.1v again even though the car was used multiple times each day. Same process this week 12.6v down to 12.1v after a couple of days again used every day. The Battery (and car) is 12 months old and I've had no issues with it.

I'm starting to think that the vehicle seems to routinely only maintain the Battery to 12.1v regardless of use.

[SiR MarK WilsoN]

Hi all just been reading through this thread and would like to add my experience after buying and RX450H+ in March 2024. After the first week I spent 3 hours cleaning it as you do. In and of doors. Doors open. Boot open playing with the screen and settings. Only to find I could not start the car later. I had to call the AA from the Lexus windscreen number.  The guy got me going and all was well other than embarrassing on a new car thinking all the neighbours are watching. Anyway. A week or so later I had the ghost immobiliser fitted.  Same again he had to jump start the car after fitting as Battery dead. A few days later I cleaned car again but thought, don't leave doors open just wipe what's needed and shut each door after.  Spent only one hour cleaning. Got ready to got out to lunch with the wife in new shiny car.... Flat.  AA out again. Took 4 hours. Wife wasn't happy.  Started looking on utube for the problem. Came across a guy in America with an NX "LFST" channel he has. He explains how the Battery is charged and he bought a Bluetooth monitor to connect to the Battery,  that connects to an app on your phone. It shows you when the car is charging and even when it's not. Looks like the car decides when it wants to charge at times.  I bought one of these Bluetooth monitors off eBay. £16 "Ancel BM200 Car Battery Monitor Bluetooth 12V Battery Tester for Iphone Androidand " it cleaned my anxiety of will the car start or not when I get in.

I now clean the car in ready mode,  in EV mode as well as this shows charging on the Battery in the Bluetooth app,  as its surprising how quick the Battery can go down with the big screen on,  Led lights in the doors and roof.  

I do mostly short journeys and the app shows that the Battery can be around 40 to 60 % charged most times and soon drops when doors are left open too long. 

I did explain this to my local Lexus dealer after owning the car 3 weeks the problems we had with the Battery and they did put me a new on one. They said " Do I do short journeys?". I did agree to them I did. They suggested taking a longer journey from work now and again to add charge in the Battery. But now I have the Bluetooth app it tells you when its low or what charge it is when your near the car so I can start the car in ready mode and see it charging to a comfortable percentage.

Hope this helps as it was a very stressful time.  

[Muff12]

On 6/6/2024 at 10:02 AM, SiR MarK WilsoN said:

Hi all just been reading through this thread and would like to add my experience after buying and RX450H+ in March 2024. After the first week I spent 3 hours cleaning it as you do. In and of doors. Doors open. Boot open playing with the screen and settings. Only to find I could not start the car later. I had to call the AA from the Lexus windscreen number.  The guy got me going and all was well other than embarrassing on a new car thinking all the neighbours are watching. Anyway. A week or so later I had the ghost immobiliser fitted.  Same again he had to jump start the car after fitting as battery dead. A few days later I cleaned car again but thought, don't leave doors open just wipe what's needed and shut each door after.  Spent only one hour cleaning. Got ready to got out to lunch with the wife in new shiny car.... Flat.  AA out again. Took 4 hours. Wife wasn't happy.  Started looking on utube for the problem. Came across a guy in America with an NX "LFST" channel he has. He explains how the battery is charged and he bought a Bluetooth monitor to connect to the battery,  that connects to an app on your phone. It shows you when the car is charging and even when it's not. Looks like the car decides when it wants to charge at times.  I bought one of these Bluetooth monitors off ebay. £16 "Ancel BM200 Car Battery Monitor Bluetooth 12V Battery Tester for iPhone Androidand " it cleaned my anxiety of will the car start or not when I get in.

I now clean the car in ready mode,  in EV mode as well as this shows charging on the battery in the Bluetooth app,  as its surprising how quick the battery can go down with the big screen on,  Led lights in the doors and roof.  

I do mostly short journeys and the app shows that the battery can be around 40 to 60 % charged most times and soon drops when doors are left open too long. 

I did explain this to my local Lexus dealer after owning the car 3 weeks the problems we had with the battery and they did put me a new on one. They said " Do I do short journeys?". I did agree to them I did. They suggested taking a longer journey from work now and again to add charge in the battery. But now I have the bluetooth app it tells you when its low or what charge it is when your near the car so I can start the car in ready mode and see it charging to a comfortable percentage.

Hope this helps as it was a very stressful time.  

I too have an RX450h+ and I had the same problem, I now wash the car in Ready mode plus any other things I do around it. I didn't go for trhe Bluetooth monitor as I have fitted a permanent connection to my 12v Battery that plugs into my trickle charger, so I can just plug it in rather than relying on the crocodile clips. I have bought a USB charger (£5.99 on Amazon) that plugs into the cigar lighter, why you ask, well I'll tell you, it displays the 12v Battery voltage as well. You can also see when the traction Battery starts to charge the 12v as the voltage increases to over 14v. When and if the voltage drops below 12, I put it on trickle charge overnight. It's a right royal pain in the bum, not something you should have to do on a £70k car.

Mark, the other thing you should get yourself is a Noco boost to keep in the glove box, then you may have read that loads of us have bought one of these. Happy motoring!

[szhrmp]

I don't understand why the Lexus app doesn't warn you that the Battery is low.

My 66 plate Mercedes had this feature (and warned me couple of times during Covid).

[DavidCM]

2 hours ago, szhrmp said:

I don't understand why the Lexus app doesn't warn you that the battery is low.

My 66 plate Mercedes had this feature (and warned me couple of times during Covid).

The previous version of the Lexus app had this feature.In their infinite wisdom Lexus removed this useful feature for the "new and improved" version we have now.I thought evolution was meant to improve things.

[RONNIE W HODGEKINSON]

On 5/19/2024 at 12:17 PM, RONNIE W HODGEKINSON said:

Really Sensible Thing To keep it in The Glove Compartment..WHY would you want to put it in The Boot when you can,t Access it Easily if the 12v Battery Fails....My Opinion Only Of Course !!!

Absolutely spot on..!!!

[ColinBarber]

1 hour ago, RONNIE W HODGEKINSON said:

Absolutely spot on..!!!

Why are you quoting yourself?

[Moleman]

1 hour ago, ColinBarber said:

Why are you quoting yourself?

The only way to know you are completely right. 😁

[BonzoSPB]

This explains why my NX450+ went bananas whilst waiting for a car park to empty last summer. We were sat in the car with the doors open and the radio on for quite some time but when we were ready to go the car wouldn't start. After displaying warning messages the car did finally start and I was able to drive off. Looks like I was lucky.

[Harrier Man]

2 hours ago, ColinBarber said:

Why are you quoting yourself?

It's a technique perfected by Donald Trump, say it loud enough and often enough and it doesn't matter what the truth of the matter is.

[RONNIE W HODGEKINSON]

On 3/20/2024 at 1:01 PM, Simpson Iain said:

After monitoring the resting battery voltage for two weeks I changed the battery this morning. It was a fairly straight forward job. No error codes or messages after the change. The old battery was a Panasonic the new battery is a Yuasa YBX5027 sealed battery from the local GSF car parts depot.

Just Out Of Interest what Charge was Showing on your New Battery..Because According to One mechanic i Spoke to He said 12.2v was quite Average for a 12v Battery on a lexus.. My DB2 which i check almost Daily always shows a Charge above 12.1v and Never had any problems with the Battery..The car goes in for a Mayor Service in September so will consult the Mechanic on this issue...BTW I Think The Hybrid Battery Charge Dynamics only goes to 80%..!!!!!!

[BillSt]

1 hour ago, RONNIE W HODGEKINSON said:

Just Out Of Interest what Charge was Showing on your New battery..Because According to One mechanic i Spoke to He said 12.2v was quite Average for a 12v battery on a lexus.. My DB2 which i check almost Daily always shows a Charge above 12.1v and Never had any problems with the Battery..The car goes in for a Mayor Service in September so will consult the Mechanic on this issue...BTW I Think The Hybrid battery Charge Dynamics only goes to 80%..!!!!!!

My Battery drops to 12.1 and only 20% power after only one day. Going in for service tomorrow so will see what they say. Perhaps Battery damaged due to full discharge in my Lexus Disaster. … 

Voltage seems to gradually fall over last two days despite both charge and 30mls usage.

[Scotlex]

On 6/10/2024 at 9:43 PM, szhrmp said:

I don't understand why the Lexus app doesn't warn you that the battery is low.

My 66 plate Mercedes had this feature (and warned me couple of times during Covid).

That is a great idea. Get it added Lexus 😀

[Herbie]

This may be handy for reference:

[Hayzee]

6 hours ago, BillSt said:

My battery drops to 12.1 and only 20% power after only one day.

In my previous post you will see that this seems to be the level (12.1v) that the vehicle maintains the 12v Battery to as a matter of course. I don't understand why.

[BillSt]

While on the granny plug, the voltage is up to 12.56v.
Does this indicate it is charging the 12v Battery as well?

It has also gone up to 91% charge. ?.? after 3hrs at that level with Battery indicated as OK.

 

 

[ColinBarber]

20 minutes ago, BillSt said:

Does this indicate it is charging the 12v battery as well?

No, it needs to be at 14v+ to be charging correctly.

Is the vehicle actually EV charging or is it just with the charger connected and waiting for a scheduled charging time? All that appears to be happening is that the 12v supply is not coming from the Battery, which will stop it discharging, but it isn't enough voltage to actually charge it up.

[BillSt]

13 minutes ago, ColinBarber said:

No, it needs to be at 14v+ to be charging correctly.

Is the vehicle actually EV charging or is it just with the charger connected and waiting for a scheduled charging time? All that appears to be happening is that the 12v supply is not coming from the battery, which will stop it discharging, but it isn't enough voltage to actually charge it up.

It is actually charging the EV Battery but on the 2kw granny lead.

The history shows only 4 very short spikes up to 14v while I was driving. Does not seem enough to charge from 20% to 90%. Something wrong here either with the monitor’s understanding or mine (or both).

[ColinBarber]

2 hours ago, BillSt said:

Does not seem enough to charge from 20% to 90%. Something wrong here either with the monitor’s understanding or mine (or both).

How well is it connected to the Battery? I wonder if there is resistance in the connection which would result in the measured voltage being lower than reality - do you have a volt meter to confirm?

[Simpson Ian]

11 hours ago, RONNIE W HODGEKINSON said:

Just Out Of Interest what Charge was Showing on your New battery..Because According to One mechanic i Spoke to He said 12.2v was quite Average for a 12v battery on a lexus.. My DB2 which i check almost Daily always shows a Charge above 12.1v and Never had any problems with the Battery..The car goes in for a Mayor Service in September so will consult the Mechanic on this issue...BTW I Think The Hybrid battery Charge Dynamics only goes to 80%..!!!!!!

I have DB2 unit on the car that acts as a GPS tracker and also monitors Battery voltage.
The DB2 device shows that the new Battery has a consistent resting voltage of about 12.7 volts. After a drive the voltage goes up to 12.8 volts for a few hours before falling back to 12.7 volts. When driving the Battery voltage (system voltage) goes up to 14.4 volts.
 

 

[Muff12]

On 7/12/2024 at 9:46 AM, BillSt said:

My battery drops to 12.1 and only 20% power after only one day. Going in for service tomorrow so will see what they say. Perhaps battery damaged due to full discharge in my Lexus Disaster. … 

Voltage seems to gradually fall over last two days despite both charge and 30mls usage.

I have an RX450h+, I use a small usb charger in the auxiliary socket that displays the voltage of the 12v Battery when the car is "started" (photo attached). The photo shows the voltage with the car in Ready mode also attached is a photo of my Battery tester taken at the same time. The 3rd photo is of the tester after I have switched off the car. If I am correct the photo of the USB charger and the volt meter show the 12v Battery is being charged.

 

[Hayzee]

I have been away for the past 10 days with the car left on the drive. I charged the 12v Battery to 12.6v before leaving home and put the car into ready then immediatly turned the car off so that I could see how much the ready mode took out of the 12v Battery. It went down to 12.4v after a single ready mode. 

So 12.4v is what the Battery had in it as I went on holiday, and 10 days later the car started into ready mode without a problem. I'll check the Battery level again shortly, but my guess is it will be around the 12v level. If so my previous post suggesting, at least in my case, that 12.1v is what my 450h seems to maintain the Battery level to on an ongoing basis.

[RONNIE W HODGEKINSON]

20 minutes ago, Hayzee said:

I have been away for the past 10 days with the car left on the drive. I charged the 12v battery to 12.6v before leaving home and put the car into ready then immediatly turned the car off so that I could see how much the ready mode took out of the 12v battery. It went down to 12.4v after a single ready mode. 

So 12.4v is what the battery had in it as I went on holiday, and 10 days later the car started into ready mode without a problem. I'll check the battery level again shortly, but my guess is it will be around the 12v level. If so my previous post suggesting, at least in my case, that 12.1v is what my 450h seems to maintain the battery level to on an ongoing basis.

Exactly Colin Mine does The same..!!!!

[BillSt]

19 hours ago, ColinBarber said:

How well is it connected to the battery? I wonder if there is resistance in the connection which would result in the measured voltage being lower than reality - do you have a volt meter to confirm?

It is very well connected (clamped spades) and I have confirmed with digital volt meter.

I have little confidence in the charge percentages given by the monitor while Battery is connected to the car. (Photo below). The voltage however seems reliable. I have only tested for a few days and each has had the car run and EV recharged. The voltage trace is interesting and shown below.

 While driving the voltage only occasionally goes up to the 14V charge level. I suspect when Auto EV/HV kicks into HV mode. While in EV mode, the ~12.56V indicates the trickle charge.

While on the granny lead, the voltage (~12.56) indicates a trickle charge (perhaps 1A) while the EV Battery is being charged, When the charge ends the voltage drops to ~12.35 then over the next few hours gradually drops down toward the 12.1 level ( there is a sudden momentary drop when I disconnect the lead)

It will be interesting to see the monitor trace if the car is not used over a few days and while loading the car with doors opening but not in READY mode.

At least the monitor should prevent the total discharge disaster but readings of voltage will be needed as the Charge alarms may be unreliable.

 

[ColinBarber]

On 7/13/2024 at 3:44 PM, BillSt said:

While on the granny lead, the voltage (~12.56) indicates a trickle charge (perhaps 1A) while the EV battery is being charged,

That's not really how trickle charging works. You limit the current, not lower the voltage below 13v, otherwise the chemistry with a lead acid Battery won't allow it to charge, certainly not to full capacity.