New 12v Battery perfectly fine after 18 days on holiday

[hintonwood]

As mentioned on this forum previously, I killed the 12v Battery about 18 months ago when washing the car and had to be boosted by the AA. Lexus checked the Battery and said it was fine. About 6 months after that it failed when loading the car to go on a day trip. Again Lexus said it was fine and wouldn’t replace it. At the time I said to them that the Battery often read 10.9 or 11.1 volts across the terminals but they wouldn’t budge.

I have since always put the car in ready mode for any time it is unlocked for loading, cleaning etc.

I bit the bullet and bought a new 12v replacement Battery from Lexus at it’s last service because I was suspecting that with my 18day holiday and the car stood out in the cold on my drive, I would return to a dead car. Having a dead car is only a minor inconvenience as I have a Booster, but I am sure the dead Battery events cause irreversible damage the cells.

Anyway. 18 days later and it has opened and started perfectly.😬

[old man 2]

 Previous to my new NX I owned a hybrid Hyundai Tucson. The Battery system was similar to the Lexus, except that the 12V Battery was a small lithium polymer Battery, both in size and capacity.

That system used to give depleted Battery problems also, in that when the Battery was running low on charge when parked, the system would cut power to certain functions and settings which would need resetting when the car was next started. It was somewhat aggravating to start with, but as owners became used to it and realised it was normal for the hybrid version, we adapted to the system.

Some owners did however manage to deplete the 12V Battery to the point where manual entry to the car was necessary.  In the Tucson (and the Ioniq) a reset button on the dash was provided to get enough charge into the 12V Battery from the traction Battery to be able to start the car (I can't understand why Lexus haven't done similar).

I had to reset certain parameters on numerous occasions and although I never suffered a completely flat Battery, I was bothered that I might as I do leave my car unused for 3 - 4 weeks at a time.

And so to my point (apologies folks, I can't do things in shorthand) and I don't really expect people to follow my example. This is for info, whether anyone wants to do it is their choice.

The anti theft alarm on the Tucson was abysmal and hardly anyone takes notice of them nowadays anyway. As you probably already know, the interior alarm system is still using Battery power when the car is switched off, so I used to turn off the interior alarm when I was away from home for a while. Whilst not directly comparable to the Lexus as the 12V batteries are different, by using this method I was able to open and start my car after it had been left unused for 4 weeks.

Some people wouldn't want to turn off their alarm like this, but as the Tucson alarm was weak and didn't last that long I thought was worth the gamble and I did/do use a Stoplock, plus some other antitheft measures.

 

Here's a minor rant;  Manufacturers and dealers of cars should be made by law to inform the buying public that their car could be prone to these problems, the same as they may well suffer blocked GPF problems if they constantly use their cars for short journeys.

[hintonwood]

2 hours ago, old man 2 said:

Some owners did however manage to deplete the 12V battery to the point where manual entry to the car was necessary.  In the Tucson (and the Ioniq) a reset button on the dash was provided to get enough charge into the 12V battery from the traction battery to be able to start the car (I can't understand why Lexus haven't done similar).

A point that has been made many times - when calling the AA with a flat 12v Battery we are sitting on a well-charged massive hybrid Battery fully capable of “lending” a few amps to start the instruments.🤬 well done Hyundai.

[Herbie]

3 hours ago, old man 2 said:

In the Tucson (and the Ioniq) a reset button on the dash was provided to get enough charge into the 12V battery from the traction battery to be able to start the car (I can't understand why Lexus haven't done similar).

Completely different technology.

The way Lexus decided to do things was to use a pair of 12V relays as a safety interlock. If the 12V Battery has enough juice to operate the interlock it energises the hybrid system, but if not, the interlock doesn't operate and so no access to the hybrid system and/or Battery for the 12V to 'pinch' a bit of power.

[Jumper68Y]

Has anyone changed the standard Battery for a larger one? or bigger Amperage? 

I read the standard Lexus one is 53Amps, but there is a direct Bosch replacement which is 63Amps. 

There is also enough space to squeeze a slightly larger Battery in which would give longevity. 

There was some debate on if the hybrid system would actually be able to charge a larger Battery, I don't see why it couldn't, as after all its just behaving like a portable Battery charger from the Hybrid system. 

This is one I am watching closely.  

 

 

[hintonwood]

11 minutes ago, Jumper68Y said:

I read the standard Lexus one is 53Amps, but there is a direct Bosch replacement which is 63Amps. 

My NX350h was built in November 2021 and had a 60Ah Battery, per the photo.

 

Lexus replaced it for me but I cannot see the label without removing it. However, I believe the replacement to be like-for-like.

[Jumper68Y]

6 minutes ago, hintonwood said:

My NX350h was built in November 2021 and had a 60Ah battery, per the photo.

 

Lexus replaced it for me but I cannot see the label without removing it. However, I believe the replacement to be like-for-like.

Interesting, 

There is certainly enough space in there for a larger (size wise) Battery, but even a decent 60Ah Battery should be more than sufficient for the limited tasks in the NX350H so I find it odd its being drained from just cleaning a car for example for a few hours. 

I do wonder if it never actually gets fully charged. 

[stepppy]

19 minutes ago, Jumper68Y said:

Interesting, 

There is certainly enough space in there for a larger (size wise) battery, but even a decent 60Ah battery should be more than sufficient for the limited tasks in the NX350H so I find it odd its being drained from just cleaning a car for example for a few hours. 

I do wonder if it never actually gets fully charged. 

When I wash my car I leave it unlocked and have tailgate & doors open when needed and have not had any problems. I put the key out of range to stop the doors locking/unlocking during the washing/drying process.

After around 10 minutes the interior lights automatically cut out, so I wonder why some people have issues?

[old man 2]

54 minutes ago, stepppy said:

When I wash my car I leave it unlocked and have tailgate & doors open when needed and have not had any problems. I put the key out of range to stop the doors locking/unlocking during the washing/drying process.

After around 10 minutes the interior lights automatically cut out, so I wonder why some people have issues?

I tend to agree. I've only had my NX hybrid a week, but based on my experience with my previous hybrid there are ways to mitigate against running the 12V Battery down.

[hintonwood]

13 hours ago, stepppy said:

When I wash my car I leave it unlocked and have tailgate & doors open when needed and have not had any problems. I put the key out of range to stop the doors locking/unlocking during the washing/drying process.

After around 10 minutes the interior lights automatically cut out, so I wonder why some people have issues?

The first time mine went dead (mid 2022) I was washing and hoovering the car for 2 hours and opening and closing doors during that time. We were oblivious to the problem then. These days I pop it in Ready mode.

[stepppy]

5 minutes ago, hintonwood said:

The first time mine went dead (mid 2022) I was washing and hoovering the car for 2 hours and opening and closing doors during that time. We were oblivious to the problem then. These days I pop it in Ready mode.

Ahh, I guess if you are opening and closing doors then the interior lights will reset and come back on for another 10 minutes. 

I tend to wash the car overall, then do the door shuts etc. separately leaving the doors/tailgate open which is when the lights turn off. 

I use a rechargeable vacuum so that’s no drain, but like you say if in doubt put it in ready mode. 

[Scotlex]

I have left my NX for over 3 weeks (maybe 3 weeks and 3 days) and it has been OK.

[Hayzee]

19 hours ago, Jumper68Y said:

I do wonder if it never actually gets fully charged. 

My experience of checking the voltage at various times is that my 450h seems to maintain the 12v Battery at only 12.2v on an ongoing basis. Having fully charged the Battery it will soon go back to that 12.2v level. However it has not yet caused any problems

[stepppy]

It’s funny, before joining this forum I didn’t give my 12v Battery a second thought as I had just over 7 years hassle free motoring in my Prius. Only during lockdown did I invest in a smart charger which I then went on to use if I went on holiday for anything longer than two weeks. Definitely didn’t worry about leaving doors open when I washed it. 

After reading here I keep thinking about getting one of these Battery monitors that others have bought, but I don’t want to get myself into a paranoid state worrying each time it drops 😆.

Decisions decisions 🤔

[Scotlex]

46 minutes ago, stepppy said:

It’s funny, before joining this forum I didn’t give my 12v battery a second thought as I had just over 7 years hassle free motoring in my Prius. Only during lockdown did I invest in a smart charger which I then went on to use if I went on holiday for anything longer than two weeks. Definitely didn’t worry about leaving doors open when I washed it. 

After reading here I keep thinking about getting one of these battery monitors that others have bought, but I don’t want to get myself into a paranoid state worrying each time it drops 😆.

Decisions decisions 🤔

I was the same. Even with "normal cars" it has been a very long time since I had a flat Battery.

I am trying not to worry and have not bought anything as yet.😅

As said, it is even more annoying when the car has a huge charged Battery.

[Herbie]

21 hours ago, Jumper68Y said:

There is certainly enough space in there for a larger (size wise) battery, but even a decent 60Ah battery should be more than sufficient for the limited tasks in the NX350H so I find it odd its being drained from just cleaning a car for example for a few hours. 

The increase from 53Ah to 60Ah is 7Ah, which would roughly equate to 4.16 extra days if the car was left standing.

[Jumper68Y]

17 hours ago, Herbie said:

The increase from 53Ah to 60Ah is 7Ah, which would roughly equate to 4.16 extra days if the car was left standing.

So quite useful really. 

In my old Audi I changed the AGM Battery which then I had to code into the car to get it charge the Battery at the correct amperage.