I am using the car every 5-7 days, 2 hours per week. Last week I made a test - I drove the car for approx. 200km. Before the trip, the battery voltage was 12.2V. After the 200km trip, the battery voltage was 12.35V. The battery is new. It seems very weird that the battery was not fully charged after such a long trip.
I saw such behavior also after shorter trips. It seems that the car computer decides not to fully charge the battery.
For me it is a major problem, because my low-frequent driving.
Any else saw such behavior?

 

Clearly you are new this club with your first post Welcome - you have immediately landed on a Gold-mine, or a Coal-mine - depending on one's perspective.

This is characteristic of the 2nd Gen NX, 5th Gen RX and also the new RZ. Here's a thread and a post about it (from the RX forum, applies to NX similarly), but there are probably too many pages for you and others read to read - its a PhD thesis

In the RX forum, the Mod decided to consolidate all 12 V battery failure/charging posts to one thread. In the NX forum, that is not the case - but once you search, read and consolidate the NX "data", you'll find the same "12 V battery" charging issues everywhere in the NX forum as well.

 

I have many videos talking about this issue. You can go to my channel and there is a playlist talking about 12V battery issue

 

Thank you

 

I am having battery issue too. See my thread https://www.clublexus.com/forums/nx-...y-charger.html

 

Everyone talks about the Dead battery issue, but no one talks about Lexus's charging policy.
I made some tests:

I installed a battery monitoring and started monitoring the car battery during parking and driving.
I found that the car charges the battery (during a drive) only part of the time. It seems that, most of the time, the "charging policy" is to maintain the battery voltage on 12.3-12.4V. In some cases, the battery was charged to 12.5V (mostly when the car is on and idle (EV mode).

My theory about the cause of the Dead battery issue – after a long driving, the owner of the car think that the battery is full, although it might be at only 12.3-12.4V. If the next drive is after several days, there is a chance that the battery will go below 50% (and therefore the battery life will damage). After several occurrences, the battery life might be severely damaged.
For Lexus, managing the battery charging is a feature, For me its a bug.

 

This has been discussed a whole lot and part of your theory appears to be correct. There is also another problem with the power convertor algorithm between the traction battery and the 12 volt battery. Lexus has been aware of this problem for over 3 years so don't expect a solution from Lexus anytime soon.

YMMV,
MidCow3

 

@lsft clearly states the problem in his videos and some methods of detection using battery voltage. However, there are no solutions to the problem yet.

YMMV,
MidCow3

 

Giving up on Lexus, I found my own Lexus Adult Diaper™ solution.

Its working very well for me, and I no longer worry or do anything about the problem. Finally my $ 80 K investment in a Lexus is worth it (the car is fantastic otherwise), and it should work for any car.

 

Very interesting solution - what is the cost ?


YMMV,
MidCow3

 

I got it for $ 100. Depending on where you get (including availability at Walmart.com and now Amazon) - it costs between $ 100 - $ 120.

Frequently goes out of stock because of high demand, but you can leave an email alert and order as soon as its available for example - from its maker: https://lithiumhub.com/product/emergency-start/

 

This charging algorithm is not special to Lexus nor Toyota. All newer cars, the ones having start-stop system do it. 12V battery is charged up to 80% or so, then alternator is disconnected. The last 20% can be used in case of engine braking, making it kind of mild hybrid, which helps with fuel economy. It's feature not bug.
Keeping 14+ V at all times like on old cars is completely unnecessary. Leaving battery in discharged state like 50% or less for longer time sulfates it, but 70-80% is nothing to worry about.
I can see a bit of OCD with 12 V batteries on Lexus forums. It may be triggered by some real (fixed) bugs but obsession got it's own life now.

Hybrids don't have alternator but they also don't charge to 100% when in Drive, only in Park.

 

start=stop on 350 maybe 250 but not 350h or 450h+ the "hs" are the problem. you got some stuff somewhat confused.

YMMV,
MidCow3

 

I have the 450+ model. For me, the 70-80% charging is a bug.
I have an anti-theft system that required the battery for monitoring and location. This system consume about 50mAh. I am driving once in a week so, assuming that the battery is charged 70-80%, after a week, the battery will drop to below 12V. This will shortage the battery life very quickly.

 

I noticed more engine braking/revving when I use a trickle charger to top off the battery in my RX350H and then drive a bit. The battery does not seem to like being fully charged and the system will deplete it down to its happy place. I have not had any battery issues, but do trickle charge when the car will be idle for a few weeks.

My battery voltage hovers around 11.5 -12.2 when car is off. With traditional battery voltage reading charts, one might think 11.5 is close to a dead battery. But I have not found that to be the case. Probably because less AMPs are needed since the engine is started with the traction battery. Not really sure. All I know it seems to work fine.

The thing I don't understand for those who inadvertently drained the 12v in ACC mode, why doesn't the car shut down automatically when battery gets low? I had a 2005 BMW that would turn off the ACC mode when the battery hit a certain voltage level.