Any 12v battery issue with RX 450h+ plug-in hybrid?

[MrBee]

Hi

I have a 2020 RAV4 HEV and I'm thinking of getting a new RX 450h+

The Rav4 has an issue with the 12v Battery going flat, normally in winter, after 2/3 weeks of not using the car. 

I just wondered if this issue is present in the RX? 

Many thanks 

[ColinBarber]

15 minutes ago, MrBee said:

I just wondered if this issue is present in the RX? 

Yes, same on all Toyota/Lexus hybrids unfortunately.

[MrBee]

Many thanks for the quick response. It is annoying.

This December we were away for a bit and did not use the car for 3 weeks. The 12v was so flat that the jump start booster did not work. Had to put it on a Battery charge overnight. 

That could be a real pain if you left the car in a long term car park for a winter holiday.

[Barry14UK]

I suppose if your car was away while you were on a long winter holiday and safely locked away, you could leave alarm off or disconnect Battery accepting what that would entail or best of all leave on trickle charge if facility exists.  The only other way I can think of would be to couple up to another Battery temporarily.  I am not sure it would need to be same type and could be smaller to boost capacity for an extended period.  In summer you can fit a solar panel but probably not sufficient for winter.

It may be that you could get a friend to charge the car from the hybrid Battery using the prescribed Lexus procedure.

[JapFanMan2021]

Coincidentally, just yesterday I found that if you leave the tailgate open for 4 hours you will have a dead Battery ☹️ Unbelievable that the three lights in the boot are not on a timer!

[Tom,]

 After two weeks in the cruise car park at Southampton last November/December - no problem starting.

[ColinBarber]

4 hours ago, Tom, said:

 After two weeks in the cruise car park at Southampton last November/December - no problem starting.

Two weeks shouldn’t be a problem on a healthy Battery, although it would have discharged the Battery to a point where it would start to damage it and therefore the capacity may have been diminished. Three weeks is when you start to run into problems. 

[GSLV6]

I'm on my 3rd deep cycle 12v Battery in 45K miles.  They get replaced every 3 years as that's all I get out of them and they're not cheap!  My last one was fitted 2 years ago and is still going strong.  I've learned from the past so invested in a better charger/conditioner which keeps it in better health.  If there's the odd week I don't use the car, I hook it up to the charger (a Cetek charger) and it seems to be the only way to get them to last. If you run them dead flat a few times, it doesn't do them much good so better keeping them in a healthy state to avoid issues.  

[SiR MarK WilsoN]

My experience after buying and RX450H+ in March 2024. After the first week I spent 3 hours cleaning it as you do. In and of doors. Doors open. Boot open playing with the screen and settings. Only to find I could not start the car later. I had to call the AA from the Lexus windscreen number.  The guy got me going and all was well other than embarrassing on a new car thinking all the neighbours are watching. Anyway. A week or so later I had the ghost immobiliser fitted.  Same again he had to jump start the car after fitting as Battery dead. A few days later I cleaned car again but thought, don't leave doors open just wipe what's needed and shut each door after.  Spent only one hour cleaning. Got ready to got out to lunch with the wife in new shiny car.... Flat.  AA out again. Took 4 hours. Wife wasn't happy.  Started looking on utube for the problem. Came across a guy in America with an NX "LFST" channel he has. He explains how the Battery is charged and he bought a Bluetooth monitor to connect to the Battery,  that connects to an app on your phone. It shows you when the car is charging and even when it's not. Looks like the car decides when it wants to charge at times.  I bought one of these Bluetooth monitors off eBay. £16 "Ancel BM200 Car Battery Monitor Bluetooth 12V Battery Tester for Iphone Androidand " it cleaned my anxiety of will the car start or not when I get in.

I now clean the car in ready mode,  in EV mode as well as this shows charging on the Battery in the Bluetooth app,  as its surprising how quick the Battery can go down with the big screen on,  Led lights in the doors and roof.  

I do mostly short journeys and the app shows that the Battery can be around 40 to 60 % charged most times and soon drops when doors are left open too long. 

I did explain this to my local Lexus dealer after owning the car 3 weeks the problems we had with the Battery and they did put me a new on one. They said " Do I do short journeys?". I did agree to them I did. They suggested taking a longer journey from work now and again to add charge in the Battery. But now I have the Bluetooth app it tells you when its low or what charge it is when your near the car so I can start the car in ready mode and see it charging to a comfortable percentage.

Hope this helps as it was a very stressful time. 

[andy1610]

Oh yes. Bought my wonderful RX450h+ three months ago. Had dash cams fitted ok. All good… for three months… until last few days when the 12v Battery discharged, twice. Always turned on to “READY”. First time bought some booster cables, all good. Drove around for 45 mins. This morning, same again. Borrowed a booster/starter pack. 
How, why? Booked into Lexus Hayes for Friday. They asked about non standard equipment and I admitted to the dash cams, which could result in £150 diagnostic cost even though the car is under warranty…..
 

[RXtoNX]

18 hours ago, andy1610 said:

Oh yes. Bought my wonderful RX450h+ three months ago. Had dash cams fitted ok. All good… for three months… until last few days when the 12v battery discharged, twice. Always turned on to “READY”. First time bought some booster cables, all good. Drove around for 45 mins. This morning, same again. Borrowed a booster/starter pack. 
How, why? Booked into Lexus Hayes for Friday. They asked about non standard equipment and I admitted to the dash cams, which could result in £150 diagnostic cost even though the car is under warranty…..
 

If your dash cams have parking mode and are not of the type that also monitor Battery level with an auto cut off then that is likely to be the culprit.

[Tom,]

Half an hour with doors and boot open while eating sandwiches during the hot weather last week and my RX450h+ 12 volt Battery was flat. Fortunately I carry one of those tiny lithium Battery jump starters. Cost about £50 on amazon and wouldn't be without it. Recommend every Lexus owner to carry one.

Tom

 

[andy1610]

Guess what? Was the dash cams after all. Have now set up parking mode and Battery protection and all good. Thanks for the excellent advice  Paul. 
Tom, I’ve learnt the hard way to keep the car in READY mode when lunching or similar. 
Apart from that, a wonderful car, nannying bings and bongs aside. 

[andy1610]

On 8/9/2024 at 7:26 PM, andy1610 said:

Guess what? Was the dash cams after all. Have now set up parking mode and battery protection and all good. Thanks for the excellent advice  Paul. 
Tom, I’ve learnt the hard way to keep the car in READY mode when lunching or similar. 
Apart from that, a wonderful car, nannying bings and bongs aside. 

Ha! 12v battery/dashcam issue back again! Had to jumpstart this morning.
Going to check those cam settings again. 🙄

[JCT]

LEXUS NEEEDS TO SIMPLY MAKE THE LITHIUM Battery PART OF THE CIRCUTRY TO MAINTAIN THE 12V SYSTEM - THE PASSIVE CHARGE CONCEPT IS NOT EFFECTIVE FOR ANY LONG TERM SHORT RUN OPERATION AND USEAGE.

THE ONLY REASON THEY DIDN'T DO THAT WAS SO THE TH FULL HP WOULD BE AVAILABLE ON DEMAND AFTER THE ALL ELECTRIC OPERATION FULLY USED THE Battery ELEMENT ALLOCATED TO FULL ELECTRIC OPERATON (ie In consistent short distance operation as full electric car - which I did until the pattery failed - now I have a 12v separate charge method.--HOPEFULLY LEXUS MAKES THE SOFTWAR MODIFICATION NECESSARY TO HAVE THE LITHIUM Battery ALSO COMMITTED TO MAINTAIN ADEQUATE CHARGE IN THE 12V SYSTEM.