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.