12V battery problem

[David Williamson]

Good morning, I have a NX450 h+ delivered in April and has 5500 miles on the clock. Yesterday whilst sat in the vehicle, waiting for my wife to come back from shopping, I had the DAB radio on listening to the Ryder Cup. After about 30 mins the 12v Battery went flat, cut the power and locked me in the car! I was in a covered car park so the headlights were on Auto.
 

I called for AA assistance who came with 40 mins and discovered the Battery was down to 7v. He got me restarted and we were able to proceed on our journey. Anyone else experienced problems with the 12v Battery? Thanks

[Scotlex]

I'm not sure if you constantly run on Battery (no petrol engine) the 12v "engine battery" will eventually go flat.

You would think that "the car" would monitor everything and run the engine when required or at least give you some sort of warning.

[NemesisUK]

It's not a problem with the Battery. It's only designed to power on the computer and monitor the access systems. If you sit listening to the radio leave the car in Ready mode and the traction Battery will power everything with the engine cutting in when needed to recharge the traction Battery.

Leaving the car in IGN or ACCES mode will kill the little 12v Battery in no time, as my salesman discovered when demonstrating the car to me!

[LenT]

10 minutes ago, David Williamson said:

Good morning, I have a NX450 h+ delivered in April and has 5500 miles on the clock. Yesterday whilst sat in the vehicle, waiting for my wife to come back from shopping, I had the DAB radio on listening to the Ryder Cup. After about 30 mins the 12v battery went flat, cut the power and locked me in the car! I was in a covered car park so the headlights were on Auto.
 

I called for AA assistance who came with 40 mins and discovered the battery was down to 7v. He got me restarted and we were able to proceed on our journey. Anyone else experienced problems with the 12v battery? Thanks

My IS250 has a system whereby if you have the ignition switched to Accessories in order to just listen to the audio system, it will switch off after a set time specifically in order to avoid flattening the Battery - which can be very annoying in the middle of a programme!

I would have thought that your Lexus would have had such a system.  Is there not also some procedure that will enable you to escape from the car if the Battery is flattened?  After all, you presumably had a phone with which to call for assistance.  If that hadn’t been the case, how long before you were discovered - presumably unable even to sound the horn to attract attention!

As it’s a new car still under warranty, I would call the selling Dealer and require them to investigate the problem.  It could be a faulty Battery or charging system., or a constant drain somewhere.

Incidentally, I carry a NOCO Power Pack in my boot in order to jump start engines.  I haven’t yet had to use it myself, but it has come to the aid of others!

[Scotlex]

13 minutes ago, NemesisUK said:

It's not a problem with the battery. It's only designed to power on the computer and monitor the access systems. If you sit listening to the radio leave the car in Ready mode and the traction battery will power everything with the engine cutting in when needed to recharge the traction battery.

Leaving the car in IGN or ACCES mode will kill the little 12v battery in no time, as my salesman discovered when demonstrating the car to me!

Good bit of information - Thanks 😀

[RONNIE W HODGEKINSON]

14 minutes ago, LenT said:

My IS250 has a system whereby if you have the ignition switched to Accessories in order to just listen to the audio system, it will switch off after a set time specifically in order to avoid flattening the battery - which can be very annoying in the middle of a programme!

I would have thought that your Lexus would have had such a system.  Is there not also some procedure that will enable you to escape from the car if the battery is flattened?  After all, you presumably had a phone with which to call for assistance.  If that hadn’t been the case, how long before you were discovered - presumably unable even to sound the horn to attract attention!

As it’s a new car still under warranty, I would call the selling Dealer and require them to investigate the problem.  It could be a faulty battery or charging system., or a constant drain somewhere.

Incidentally, I carry a NOCO Power Pack in my boot in order to jump start engines.  I haven’t yet had to use it myself, but it has come to the aid of others!

I Also Carry a NOCO GB 40 Power booster in the car just for that very Reason...But as you said DO NOT KEEP YOUR RADIO ON FOR Lengthy periods in Accessory Mode.. By all Means take it to the dealership But they will tell you exactly the Same..The Science and cause of this is that cars didnt used to have all this technology drawing on the little Battery so was not a Problem BUT IT CAN BE NOW..... Golden rule DON,T DO IT..!!!

[Andy B]

1 hour ago, Scotlex said:

I'm not sure if you constantly run on battery (no petrol engine) the 12v "engine battery" will eventually go flat.

You would think that "the car" would monitor everything and run the engine when required or at least give you some sort of warning.

My previous 2018 NX300h gave me a warning (in the instrument cluster) after a short while when I was using the radio in ACC mode. I'm pretty sure that the Gen 2 NX would do the same but I've never tested it. As others have said - always have the car in READY mode when sitting in the car idle and listening to the audio. Also, I find that with the A/C and fan off and the lights switched away from AUTO, the car can stay in EV mode for quite a while before the ICE kicks in (mine is the standard hybrid).

[RONNIE W HODGEKINSON]

59 minutes ago, Andy B said:

My previous 2018 NX300h gave me a warning (in the instrument cluster) after a short while when I was using the radio in ACC mode. I'm pretty sure that the Gen 2 NX would do the same but I've never tested it. As others have said - always have the car in READY mode when sitting in the car idle and listening to the audio. Also, I find that with the A/C and fan off and the lights switched away from AUTO, the car can stay in EV mode for quite a while before the ICE kicks in (mine is the standard hybrid).

Good Advice Andy..!!!

[JayWales]

It really does seem to be a tiny Battery! 😞
I've had issues with it from having the car valeted, doors open long enough drains it.
Also my Blackvue camera in parking mode killed it, even with the option to turn it off with low Battery. I think it just drops too quick for the camera to sense it and turn it off.
So had to turn that feature off which is a shame.

I became an expert at the manual unlocking of the doors, and now have a Battery pack in the glovebox just in case - Don't put it in the boot, can't get in if Battery dead 😄

[ColinBarber]

29 minutes ago, JayWales said:

Also my Blackvue camera in parking mode killed it, even with the option to turn it off with low battery. I think it just drops too quick for the camera to sense it and turn it off.

Some models have an adjustable voltage cutoff. You need it to be set to 12v or above.

[JayWales]

Yes, it's set to the most conservative cutoff point but still manages to drain it when using parking mode

[Mike100C]

I had an NX 300h with a similar Battery issue, flat Battery warnings, in the end I fitted a NOCO Battery lead to the Battery terminals and connected this to a NOCO Genius 5 trickle charger, ( simple plug in) since then no Battery issues. I also carry a jump starter pack in my car just in case. I have just this week upgraded to an NX 450h+ Takumi and will fit my trickle charger to this for the same reason. I discovered the 12v Battery problem was created by not using the car regularly enough, therefore it wasn't receiving any charge. I did enquire if my new PHEV provided charge to the 12v Battery when plugged in, the answer was no. (This is common to most PHEV's and EV cars apparently). Hope this is of some help. There is UTube video of a guy doing this install on an NX.

[ColinBarber]

56 minutes ago, Mike100C said:

I did enquire if my new PHEV provided charge to the 12v battery when plugged in, the answer was no. (This is common to most PHEV's and EV cars apparently).

It's worth testing that if you can because it is surprising it doesn't. At least some of the vehicle's ECUs would need to be powered up to charge and therefore the 12v system would be alive.

[Mike100C]

2 hours ago, ColinBarber said:

It's worth testing that if you can because it is surprising it doesn't. At least some of the vehicle's ECUs would need to be powered up to charge and therefore the 12v system would be alive.

Hi Colin

I asked my Lexus dealer to check if the 450h+ PHEV would in fact effectively trickle charge the 12v Battery when plugged into a wall charger and it was a no it won't. Interestingly my brother owns a PHEV Ford KUGA and his Battery failed recently as he was laid up for a while (2 weeks). Unable to get in with key fob etc. Had to get a new Battery - he now carries a jumpstart kit just in case. I believe even Tesla have similar issues. Loving modern tech!

[Carolynjane]

I purchased my 2022 Lexus NX 450+ plug in hybrid and also got locked in my car when the 12v Battery went dead.  Since it was still under warranty it was towed.  Battery had to be replaced.  If you don't drive this car often enough, the Battery discharges.  My husband thinks Lexus has skimped on the 12v Battery and wonders why they aren't using Lithium 12v batteries which hold their charge longer?  Anyone know why they aren't?  

[Boomer54]

Hmm, were you towed inside the car?

[cherry1]

I have a 2022 NX450H which did the same thing to me - flat Battery with no warning and entrapping me for a while till I managed to find the non electric way of opening the door. Not a pleasant experience at all. Fortunately it happened in a quiet car park with friends who came to my assistance but even they were concerned about getting me out of the car. It was raining heavily and the windows stopped functioning too. The AA appeared after 3 hours, connected a boost to the Battery and all was well.

But why did it happen? Since my last computer upgrade visit to the garage, I noticed that all the heating  appliances such as seats and steering wheel switch on automatically until I switch them off. I had also been on the phone for the short run, hence Battery would have been draining. I never had this problem with my last car, Porsche Macan which certainly had a bigger Battery. Is Toyota skimping on the Battery? A low Battery warning light would have been helpful. 

As my partner said it could have been grievous if it was a fire or medical emergency and people couldn't get me out.

 

 

[BillSt]

Previous cars, BMW X3, Auris and RAV4, all had an automatic switch that disabled all extras except the alarm, whenever the Battery became low. When returning to the car there was a message on screen to say that had been done even though there was still enough energy in the Battery to start the car, perhaps somewhat reluctantly.

Also, with BMW, if airbags had been deployed, all doors were unlocked. Not sure if this occurs with Lexus.
 

Seems a pity that Lexus could not manage the same but may be due to the motor generator requiring more power.

[Mobeam]

15 hours ago, cherry1 said:

I have a 2022 NX450H which did the same thing to me - flat battery with no warning and entrapping me for a while till I managed to find the non electric way of opening the door. Not a pleasant experience at all. Fortunately it happened in a quiet car park with friends who came to my assistance but even they were concerned about getting me out of the car. It was raining heavily and the windows stopped functioning too. The AA appeared after 3 hours, connected a boost to the battery and all was well.

But why did it happen? Since my last computer upgrade visit to the garage, I noticed that all the heating  appliances such as seats and steering wheel switch on automatically until I switch them off. I had also been on the phone for the short run, hence battery would have been draining. I never had this problem with my last car, Porsche Macan which certainly had a bigger battery. Is Toyota skimping on the battery? A low battery warning light would have been helpful. 

As my partner said it could have been grievous if it was a fire or medical emergency and people couldn't get me out.

 

 

Just read these posts and feeling rather concerned. As a 76 year old with a disabled partner you may understand why..... should we, or I get into the same situation i.e locked inside the car, or out of it!

Given that these vehicles are of £55k plus and [was told] that they are very reliable manufacturers, this is very worrying. To read in these post that in now 2023 after similar expensive purchases, some owners are buying and fitting additional Battery leads and chargers [just in case] is surely a sad and worrying state of affairs. As I see it, right now if the same did happen [flat battery] due to no fault of my own and without any prior warnings, then I would seriously be thinking of changing.  Or am I getting over concerned?

Elias, did you eventually open the door by pulling the lever twice or some other way. I assume that if locked out of it then one would use the metal key inside the fob. But then if that happened then all the electrics would be dead, and a call to Lexus emergency would be required.

Sorry to ask these basis questions  [1] if this Battery is charged by the engine and not via the hybrid plug in.... nearly all my trips are in EV mode, so if the ICE is not used how is it topped up?

                                                          [2] is the ICE started up via this [small] Battery using a normal starter motor. If so surely that would quickly deplete it if I made a number of short stop start trips?

 

[Bluemarlin]

1 hour ago, Mobeam said:

Sorry to ask these basis questions  [1] if this battery is charged by the engine and not via the hybrid plug in.... nearly all my trips are in EV mode, so if the ICE is not used how is it topped up?

                                                          [2] is the ICE started up via this [small] battery using a normal starter motor. If so surely that would quickly deplete it if I made a number of short stop start trips?

 

As I understand it the 12v Battery is charged by the hybrid system, and so the ICE isn't used to charge it. In fact there's no alternator for it to do so. The iCE will kick in as required to charge the hybrid Battery.

The ICE is started by the hybrid system motor/generator, and so there's no traditional starter motor. The 12v Battery is only used to fire up the hybrid system.

[ColinBarber]

4 hours ago, Mobeam said:

[1] if this battery is charged by the engine and not via the hybrid plug in.... nearly all my trips are in EV mode, so if the ICE is not used how is it topped up?

[2] is the ICE started up via this [small] battery using a normal starter motor. If so surely that would quickly deplete it if I made a number of short stop start trips?

as above

1] the 12 v aux Battery isn't charged by the engine, it is charged by the vehicle's low voltage supply which is provided by the hybrid system when it is in Ready mode. That energy comes from the high voltage traction Battery, regenerative brakes or petrol engine as determined by the system. It isn't something you need to worry about or can control.

2] the petrol engine is started from one of the electric motors within the hybrid system, powered from the high voltage traction Battery. The 12 v aux Battery only provides standby power for retaining memory settings, the alarm and door locking/unlocking, and powers up the vehicle's systems to allow it to get into Ready mode when the hybrid system takes over.

[The_Doctor]

1 hour ago, ColinBarber said:

as above

1] the 12 v aux battery isn't charged by the engine, it is charged by the vehicle's low voltage supply which is provided by the hybrid system when it is in Ready mode. That energy comes from the high voltage traction battery, regenerative brakes or petrol engine as determined by the system. It isn't something you need to worry about or can control.

2] the petrol engine is started from one of the electric motors within the hybrid system, powered from the high voltage traction battery. The 12 v aux battery only provides standby power for retaining memory settings, the alarm and door locking/unlocking, and powers up the vehicle's systems to allow it to get into Ready mode when the hybrid system takes over.

As above [1] there is a component called a DC/DC converter which powers the low voltage (12 V) systems from the HV supply.

Because [2] the 12 V Battery is essentially only there to retain settings and power the vehicle up it doesn't need to be as large as one that has to have the capacity to crank an ICE for a cold start.

[Harrier Man]

I share the understanding of the system as described by Colin and the doctor but why is it then that several people have had problems with the Battery? It seems hard to identify the true cause of the drain. Can the Battery really be drained so much by having the doors open during valeting or from having a dashcam live when the car is parked or from having the alarm triggered? Shouldnt there be some protection to prevent the Battery from draining below a critical level? I can't believe there isn't. Some have had batteries replaced but quality assurance is pretty good these days so the number of genuinely faulty batteries seems high to me. Are they being replaced just because it's an easy thing to do?

[Scotlex]

13 hours ago, ColinBarber said:

as above

1] the 12 v aux battery isn't charged by the engine, it is charged by the vehicle's low voltage supply which is provided by the hybrid system when it is in Ready mode. That energy comes from the high voltage traction battery, regenerative brakes or petrol engine as determined by the system. It isn't something you need to worry about or can control.

2] the petrol engine is started from one of the electric motors within the hybrid system, powered from the high voltage traction battery. The 12 v aux battery only provides standby power for retaining memory settings, the alarm and door locking/unlocking, and powers up the vehicle's systems to allow it to get into Ready mode when the hybrid system takes over.

Thanks for this.

I am still trying to understand how it all works.

[Scotlex]

I am still a new NX owner and was a bit concerned about the 12v Battery etc..

My NX was fully charged and then not used for 3 weeks. 

I had no issues and the car just "started" and drove as normal which is quite reassuring 😀😀