Lexus RZ chronicals-by my wife

[apex96]

This does seem like a strange issue given the fact that a high voltage battery is on board. @J Alynn this describes the majority of my driving so i will have to be diligent.

Not really a strange occurrence once you gain knowledge on how the systems work. The 12 volt battery provides the power for the contactors to open and close the circuit on the HV battery. When you shut the car off the contactors open so the HV battery isn't providing any power (can't trickle charge the 12 volt on a lot of EVs). I believe all EV manufacturers have programming to have the car "check" the condition of the 12 volt battery but there's no standard frequency written up yet for such checks. This means the vehicle can inadvertently let the battery drain to far down before it wants to close the contactors and draw energy from the HV battery to charge the 12 volt.

We haven't had a 12v battery go bad since we moved to all electric. We leave our vehicles on their plugs and subscribe to the ABC (Always Be Charging) philosophy.

Same as Space, we leave it plugged in a charging at all times, it will idle itself and trickle charge (balance cells) on its own while on the charger. Have yet to have a 12 volt battery failure in the almost 9 months of ownership. We have over 25,000 miles on it now (wife drives a LOT for work, she does get mileage though! ).

 

[cyure]

Not really a strange occurrence once you gain knowledge on how the systems work. The 12 volt battery provides the power for the contactors to open and close the circuit on the HV battery. When you shut the car off the contactors open so the HV battery isn't providing any power (can't trickle charge the 12 volt on a lot of EVs). I believe all EV manufacturers have programming to have the car "check" the condition of the 12 volt battery but there's no standard frequency written up yet for such checks. This means the vehicle can inadvertently let the battery drain to far down before it wants to close the contactors and draw energy from the HV battery to charge the 12 volt.


Same as Space, we leave it plugged in a charging at all times, it will idle itself and trickle charge (balance cells) on its own while on the charger. Have yet to have a 12 volt battery failure in the almost 9 months of ownership. We have over 25,000 miles on it now (wife drives a LOT for work, she does get mileage though! ).

Okay so let’s say you are on a trip with your new Scout BEV, and let’s say you stay overnight and aren’t able to charge while you are on your way home from the factory, what happens? Does the 12V lose charge that fast?

 

[apex96]

Okay so let’s say you are on a trip with your new Scout BEV, and let’s say you stay overnight and aren’t able to charge while you are on your way home from the factory, what happens? Does the 12V lose charge that fast?

It should not lose charge that fast. It will likely take a number of days 4-5+ days. The other issue with EVs is that the manufacturers a placing smaller and smaller 12 volt batteries in them because they don't need a ton of energy and don't require a large amperage to start and run. With small batteries comes less energy store capacity and they can die quicker than the large 12 volts in an ICE car.

 

[cyure]

It should not lose charge that fast. It will likely take a number of days 4-5+ days. The other issue with EVs is that the manufacturers a placing smaller and smaller 12 volt batteries in them because they don't need a ton of energy and don't require a large amperage to start and run. With small batteries comes less energy store capacity and they can die quicker than the large 12 volts in an ICE car.

Okay so the rule at home should be plug it in, set it to charge to 80%.

Okay here’s the next question. Let’s say I plug it in at home and dont go anywhere for a couple days. Once it gets to 80% just leave it plugged in?

By the way if I didn’t have all of you to answer all my questions I don’t think I would be getting a BEV.

 

[Scout_Lookout]

Okay so the rule at home should be plug it in, set it to charge to 80%.

Okay here’s the next question. Let’s say I plug it in at home and dont go anywhere for a couple days. Once it gets to 80% just leave it plugged in?

By the way if I didn’t have all of you to answer all my questions I don’t think I would be getting a BEV.

I always leave my truck plugged in no matter what. It's just second nature now, when I pull into the garage to just hop out and plug in. However, due to my charging schedule preference it doesn't start charging right away, instead it will only start charging during what I have set as the off-peak hours. But as I mentioned before I always leave mine plugged in, and you can just think of it like a battery tender.

 

[J Alynn]

Not really a strange occurrence once you gain knowledge on how the systems work. The 12 volt battery provides the power for the contactors to open and close the circuit on the HV battery. When you shut the car off the contactors open so the HV battery isn't providing any power (can't trickle charge the 12 volt on a lot of EVs). I believe all EV manufacturers have programming to have the car "check" the condition of the 12 volt battery but there's no standard frequency written up yet for such checks. This means the vehicle can inadvertently let the battery drain to far down before it wants to close the contactors and draw energy from the HV battery to charge the 12 volt.


Same as Space, we leave it plugged in a charging at all times, it will idle itself and trickle charge (balance cells) on its own while on the charger. Have yet to have a 12 volt battery failure in the almost 9 months of ownership. We have over 25,000 miles on it now (wife drives a LOT for work, she does get mileage though! ).

Apparently it’s a bigger issue with Lexus as there are hundreds of posts about the same issue occurring. And who knows how many others who just assume dead battery and don’t follow up with Lexus

 

[apex96]

Apparently it’s a bigger issue with Lexus as there are hundreds of posts about the same issue occurring. And who knows how many others who just assume dead battery and don’t follow up with Lexus

Unfortunately the battery charge issues also plaque all of Toyota motor company and Subaru since they platform share. So it’s three major automakers (Lexus, Toyota, and Subaru) affected. This is likely something they can solve via software updates though.

 

[SpaceEVDriver]

Okay so the rule at home should be plug it in, set it to charge to 80%.

Okay here’s the next question. Let’s say I plug it in at home and dont go anywhere for a couple days. Once it gets to 80% just leave it plugged in?

By the way if I didn’t have all of you to answer all my questions I don’t think I would be getting a BEV.

Always (as often as practicable) be plugged in.

 

[RodorW]

@SpaceEVDriver commebted above and it’s encouraging as that is exactly what my wife’s research noted (not that I’d ever doubt Space) so it just a learning curve and something nobody educated us on. As for the keys and draining the battery-this is definitely more of an EV thing because my Accord hybrid sits next to hers and my keys are closer so unless I’m like 24” outside of the range-which is possible, I’ve never had a 12v issue on the hybrid. So lots of research on plug in and program pre starts, charge times/percentages and that should help on a bunch. And to my wife’s point, maybe SM will have a specific FAQ or tips/tricks page for new EV drivers to help everyone avoid these odd nuances.

We leave our Keys in the laundry/mud room connected to the garage, the hornet doesn’t have any sort of greeting or approach sequence, but the blazer does and it seems to be the perfect distance as once the key crosses the threshold of the door

https://imgur.com/a/1raP7cA

 

[bwdavis7]

When my wife's Lexus NX-300 Sport (turbo-ICE) was new it wasn't driven much as she was afraid to park it at WalMart or Alde (protecting it from idiots and those that don 't care about others' property). After she totaled her Civic (everybody was OK) she had to drive her Lexus regularly and of course some goof ball backed into it with a trailer hitch at Alde and left the scene.

Sorry, I got on a tangent. Anyway, while the Lexus stayed garaged for several days on end, the battery would drain. I believe several things go on with that car when it sits alone. Occasionally, we have caught it making a noise like the fuel pump is running. Maybe some self diagnostics...IDK. I am guessing the computer is always on and possibly updates while nobody is watching. The battery died frequently, so during that time I mounted a permanent trickle charger under the hood and it was "always be charging". Now, she drives it enough that I don't trickle charge anymore.

When I bought my Ioniq 5 this year, I was aware that Hyundai also had issues with the 12V battery staying charged. Some of this was owners not being aware that they should not run the car in "Accessory" mode for long periods of time because the traction battery is not maintaining the 12v battery in that mode. The Ioniq 5 has a "Utility" mode that is documented in the owners manual that is intended to maintain the 12v using the traction battery when needed for long periods of needing to run accessories.

Also, when I purchased my Ioniq, I intended to have the dealer install a 12v AGM battery as part of the deal. Many owners had done this upgrade to their Ioniqs with some success. When I checked the 12v battery that was installed in the Ioniq, apparently Hyundai is installing AGMs in the 2026 models. I have not had an issue with mine so far, but for backup, I carry a battery boost pack and compressor (the Ioniq comes with Fix-Al-Flat and I am not putting that goop in my tires. I'll plug the tire myself or call for a tow).

 

[J Alynn]

We leave our Keys in the laundry/mud room connected to the garage, the hornet doesn’t have any sort of greeting or approach sequence, but the blazer does and it seems to be the perfect distance as once the key crosses the threshold of the door

https://imgur.com/a/1raP7cA

You are very lucky

 

[J Alynn]

When my wife's Lexus NX-300 Sport (turbo-ICE) was new it wasn't driven much as she was afraid to park it at WalMart or Alde (protecting it from idiots and those that don 't care about others' property). After she totaled her Civic (everybody was OK) she had to drive her Lexus regularly and of course some goof ball backed into it with a trailer hitch at Alde and left the scene.
Yeah-the short commute, less than 20 minutes per Lexus is part of the issue as the traction battery doesn’t hit a point where it charges the 12v. So we will try our various options and post more as she learns more and we see what works and what doesnt
Sorry, I got on a tangent. Anyway, while the Lexus stayed garaged for several days on end, the battery would drain. I believe several things go on with that car when it sits alone. Occasionally, we have caught it making a noise like the fuel pump is running. Maybe some self diagnostics...IDK. I am guessing the computer is always on and possibly updates while nobody is watching. The battery died frequently, so during that time I mounted a permanent trickle charger under the hood and it was "always be charging". Now, she drives it enough that I don't trickle charge anymore.

When I bought my Ioniq 5 this year, I was aware that Hyundai also had issues with the 12V battery staying charged. Some of this was owners not being aware that they should not run the car in "Accessory" mode for long periods of time because the traction battery is not maintaining the 12v battery in that mode. The Ioniq 5 has a "Utility" mode that is documented in the owners manual that is intended to maintain the 12v using the traction battery when needed for long periods of needing to run accessories.

Also, when I purchased my Ioniq, I intended to have the dealer install a 12v AGM battery as part of the deal. Many owners had done this upgrade to their Ioniqs with some success. When I checked the 12v battery that was installed in the Ioniq, apparently Hyundai is installing AGMs in the 2026 models. I have not had an issue with mine so far, but for backup, I carry a battery boost pack and compressor (the Ioniq comes with Fix-Al-Flat and I am not putting that goop in my tires. I'll plug the tire myself or call for a tow).