Glad you’re not dealing with this. No parasitic drain detected. Have no problem with it holding a charge even after two weeks of not driving. Problem seems to arise after driving short hops on EV for a month. The months where I drove an hour out of town once, no dead battery. Months when I didn’t take that one long drive, dead battery. The final moments of battery death those times were preceded by playing with settings on ACC mode (I don’t do this anymore) for about 15 mins, and then the other time, I left the drivers door and back hatch open for about 20 mins while offloading. What ordinarily would not completely discharge the 12 volt ends up doing just that because the short trips on EV mode do not seem sufficient to recharge this installed battery. And now that the battery has been fully discharged twice, it’s now permanently damaged and will not last a normal battery lifespan. So I’m already looking toward my next, hopefully more powerful, 12 volt.

 

Folks;

Attaches is a snip of part of page 156 of the manual. Pretty clear on how ACC mode works and what not to do.

 

Wished all it did when on ACC after 20 mins is switch off as it states in the manual. But it will definitely discharge the entire battery if it’s already low and you sit in park with hybrid system off. Learned the hard way. Never had a vehicle do this on me before so caught me by surprise. I now leave the NX on ready mode when parked and messing with the computer. No reason to switch it to ACC mode.

 

You would think that was the case, but charging the traction isn’t enough to charge the 12 volt. In fact, if you leave the charge cord plugged in after the traction battery is topped off, the computer monitoring the cord will draw down power from the 12 volt until you unplug it. So you should unplug after the traction battery is charged up or you could kill the 12 volt. (At least the low mileage folks more susceptible to dead battery issues)

 

This is where the AGM battery is essential becuase the constant discharge and recharge cycles kill flooded batteries not to mention high Amp draws from all the electronics.

 

I am new to the Hybrid and am going to have an installation done soon, what instructions should I give the installer to prevent having any 12V issues?
How can the doors be left open for a few hours so as not to drain the 12V battery?

Under what conditions would I need to activate the "ACC" mode ?
So, is the message here to NEVER start or press the Power button unless I hit the brake pedal first?

Thanks for your response

 

@LeX2K I can vouch for Odyssey batteries as I have PC1200MJT installed in my non Lexus car. For my aftermarket air suspension along with two decent size air compressors setup with air management the Odyssey batteries powers up great! Odyssey batteries fires up no problem in the WA mild cold (gets as low as 20 degrees F) But the problem is, you can't buy a direct OEM fit Odyssey battery, you need to measure out OEM battery tray or battery compartment and see what Odyssey battery can fit. Overall would recommend Odyssey batteries! I would upgrade in my RX 500h but the wife said I can't touch the RX but she did request for JDM window visors for the RX buhaha!

 

Unfortunately I did a search on the ODYSSEY website, plugged in the NX450 to find the right sized battery, and it came back with 0 matches.

 

Thanks for the info. I'm sick and tired of just okay batteries from places like Canadian Tire.

 

Input 2023 instead of 2024.

 

Well thus far in each cold spell over 2 winters, the 12V battery has failed and this time will require replacement again (this will be 12V battery #3). I'm probably going to buy one at Costco this time so I'll have a spare after the dealership replaces the current one. Apparently that will require Lexus roadside assistance to tow it 300+ kilometres to the nearest dealership. So be it. If a vehicle can't be expected to start in cold weather without the 12V battery being trickle-charged constantly every time it's parked, then Lexus deserves their extreme roadside assistance costs. Unfortunately it's more than a week wait for a tow currently. At least our NX is at home and we also have a second vehicle that starts every time, and typically isn't even plugged in.

 

Sorry to hear that, crazy! But they are replacing the battery? So they say it’s a battery problem? Down here in the states the dealers say there’s nothing wrong with the battery, just how Toyota designed the recharge mechanism so that people who only take short trips consistently drain the 12 volt until it dies. But in your case they’ve said your batteries have been defective?

 

I did dual AGM in Dodge Cummins,and AGM in my Jeep.Both failed like in 2 yrs,went back to plain ol lead acid,both did much better.

 

AGM cooks in hot weather, and doesn't have as much juice in very cold temperatures. So why buy one again? Unless you have a hybrid and have no choice.

 

Well it's an identical situation to what happened last winter and the battery was replaced under warranty then as it failed their battery load test. Currently I am trickle charging it for 20 hours which has only raised the voltage from 2.7v to 6v. When I try to boost it or use a larger charger, the booster or charger just fail with errors that make little sense. It's as if the battery voltage is too low to be helped and the long path or circuitry from the front to the back of the vehicle doesn't help.

It's also 42 below Celsius and in my experience, lead acid batteries are irrevocably damaged with so little voltage in these temperatures. The question becomes one of how was the voltage allowed to drop so low? My wife started the car in EV mode this morning but a few seconds later when the gas engine tried to start, everything went dead, dead, dead. Again.