RandallC

Was away on business, when I got a late night call from my wife who was locked out of the NX450. There was absolutely zero battery left, and she had to get it towed (by Lexus) to a dealership. She used the mechanical key to get in, and even holding the key fob to the start button, there was absolutely nothing. (No lights, indicators, etc - just completely dead.) The dealer (Don Valley North Lexus) insinuated that it was my wife's fault and she should know better, but honestly, she has no idea how this could have happened, and left the dealership feeling like she was being treated as "the dumb broad".

I am guessing that somehow she left the car with the accessory power on, and this drained the battery. And the "fix" at the dealership was to recharge the battery. But she wasn't gone from the car for more than 15 minutes (she was getting take-out food), and presumably with all of the electronics, there should be at least some sort of "fail-safe". Any ideas on how to prevent this from happening again?

Thanks!

LeX2K

Did the dealer test the battery? It could be defective. Whatever the cause the dealer has an obligation to resolve the problem not talk down to your wife. I would file a complaint with Lexus. What dealer were you at specifically.

Edison_Chen

Does the vehicle driven often? I noticed the 12v battery drains quicker on hybrids than gasoline versions. One time, I was playing with the settings in my garage while in ACC mode/on mode (not ready) and the head and tail lights were on. After maybe 30 mins or so, the 12v battery died, the car refused to start and I had to jump start it from under the hood. Now, if we don't drive the car for several weeks or if we only do short trips, I will use the battery tender and charge the battery overnight to prevent the 12v from depleting.

lsft

You should complain to the head of the service department at DNVL. I don't think you can leave the car in accessory mode and lock the car. If she had to use the mechanical key which means the car was locked. If you do drive your vehicle in short distances the 12V battery tend to drain more than you recharge it while the car is in ready mode. The car will automatically power off after 1 hour, or in accessory mode, I have seen it automatically turning off. there is a fail safe to it. But I think it's not related to the accessory mode issue.

midcow3

@RandallC first I am sorry they treated your wife that way; that is terrible and uncalled for. For what you described it sounds like just a battery failure. Lexus should have checked the battery and replaced it if necessary. My car is 16 months old, I just took it to Lexus for 10K service. Lexus killed my battery in their car wash and had to replace it. MY Lexus service experience was bad , but that is a discussion in itself for another time.

Lexus normally follows up with a survey, I would note your wife's treatment in the survey. However, and even better way to get the Lexus dealer's attention is to post a review in Dealerrater. Car Dealers do no like to have negative reviews in Dealerrater https://www.dealerrater.com and normally address and resolve any issues brought up immediately.

Good luck.

YMMV,
MidCow3

NX450Guy

This is my first post in the forum as I had to respond to this. It’s crazy that the manufacturer and dealerships aren’t more on top of this recurring problem with the NX.

This happened to me at 90 miles and 300 miles till I figured out on my own what causes the complete drain of the 12v battery.

The first time the battery completely died was when I was getting familiar with the NX computer settings sitting in my garage on ACC mode. After about 20 minutes, the wipers turned on, the display went blank, then flickered and made noises like it was possessed. The engine wouldn’t turn off even with a long press of the start button. I jumped out and it finally died down. I shut the doors, hoping for some sort of reset. But now there was no juice to even open the doors again so I used the hard key to get in. I called Lexus (AAA), and they towed it in.

The dealership proudly told me hours later that the battery was fine. They couldn’t tell me what happened and just said don’t use ACC.

Then two months later I left the side door and hatchback open to unload supplies for 30 minutes, and found the NX quietly died this time. No juice at all. I had it jumped by Lexus/AAA, and drove it to the dealership where they once again reassured me nothing is wrong with the battery and refused to replace it. They kept it for days to see if it held a charge or if any accessories like the OEM dash cam parasitically drains the battery. Nope, they found nothing wrong (and no evidence of foul play other than the dead body!).

So now I’m mad as I don’t need this expensive hunk of metal dying on me randomly. I bought a small charger to keep in the NX at all times and scoured the internet for clues. This is what I discovered:

1. You will not get any warning if the 12v is about to die. No fail safe of any kind. Yes, a light will shut off, but there are other ways your 12v is slowly loosing juice and no pop up on your computer screen will tell you.

2. If you only take short trips (20 mins or so), you are probably draining the 12v. The NX needs to run at least a solid 40mins/hour at one time once a month to fully charge the 12v. (This is my experience, at least). I usually only go on short trips, so my 12v was not getting a chance to recharge. How much you use AC or heat, etc., on these short tips will also impact how quickly you drain the 12v.

3. If you have no reason to go on long trips and think that you shouldn’t have to change your driving habits to nursemaid a luxury vehicle, I was told by one dealership that sitting in your driveway with the NX on “ready” mode for 30 minutes every so often will also charge up your 12v. However, another dealership vehemently said you have to turn the wheels/drive in order to charge the 12v (note: we are not talking about the traction battery).

I haven’t empirically tested the ready mode charging method. I changed how I drive the NX. I take it instead of my other car when I visit a friend an hour away. Since then I haven’t had my battery die. Also, if I’m going to be exploring the computer systems in the garage, I leave it in “ready” mode just in case.

But get a jump starter until Lexus makes a more robust 12v, or includes a warning mechanism so we know we’re draining the battery. I got the NOCO Boost GB40. It’s small, and the charge lasts a year before you have to plug it in to recharge.

This battery drain problem has been going on since 2022, wish Lexus would address it.

Good luck!

weaver483

This is a known problem with the NX and many on here have experienced dead 12v batteries. My advice is be careful to not leave any of these electric doors open to long since that will drain the battery. Of course there several other thiings that will also drain the battery. There are to many electronics running on just the 12v and hopefully Lexus will fix this eventually in future model years.

midcow3

Get one of these; well worth it for $59.48


YMMV,
MidCow3

azieba

I second the NEXPOW, all 4 of our vehicles have them. My neighbors v8 F150 was dead last year and we used my NEXPOW to jump it without issue.

gcskoor

Unfortunately, I have had the same problem on the 22 350h. If you leave a door open or even worst using ACC even for a few minutes, the battery will die very quickly. And yes, get a battery jumper pack like the NOCO. And keep it in under the front seat not the hatch hidden storage area, since if the battery dies, you can not get to the hatch area to access the jump starter unless you like climbing over the back seats to get to it. There is no manual key on the hatch.

Ask me how I know. LOL I also now use a trickle charger much more aggressive than for any car I have ever owned. If I don't drive it for a week, I put it on the trickle charge (a NOCO 2 amp model). Once you get burned, it is enough to make you very cautious.

Luckily my start failures were at home, so I was able to recharge the battery without needing a tow.

Sorry about your wife situation.

kent2174

Above info is great, but i have a question about 350h. Isn't the battery in the hatch? If your battery is dead, how does the back hatch door open to gain access to 12v battery to jump?
Is it just a matter of attaching positive to positive, neg to neg? I am thinking about getting the mentioned Nexpow.

Droid13

There are jump connection points under the hood.

blueless

Can I avoid this problem by locking the car's doors whenever I leave the car?
I'll be away for about two weeks over Christmas/NY.

OldManToad

I also bought a NOCO GB40 charger to keep in my NX 350h. We have been on two trips over two weeks long where the car has been at the airport. Neither time have we had any issues with the battery and have not had to use the GB40 yet with the NX. However, I have used it on my wife's ice car a couple of times and it worked great. I highly recommend every NX owner to have one of these.

kent2174

Regarding these jump starters, I found in lexus manual the red to red under fuse box.
But the negative goes to left side of engine to some bolt per the diagram.
These chargers come with short cables.....where do you place the negative?