Just a poke in the dark but if the car is garaged it is a good idea to use the fob to lock the doors and then store the smart key fob a couple of rooms away from the car. Even better, if the car is going to sit for a while turn the smart key system off - check the manual for the switch location.

Best idea is to purchase a battery tender that can be hard wired directly onto battery cables and has a plug outside the grill. Makes it easy to plug it in and no possibility of shorting the battery connecting and disconnecting a tender every time you drive the car.

 

By coincidence, the keys are stored as described in paragraph one. If they were not, are you thinking the car turns on because something happens if the keys are closer?

I do plan to buy a battery tender like that.

The mechanic called me yesterday and the alternator is dead. Why they did not discover this the first two times the car was in there, I do not know.

 

This has been a problem in my 2006 LS430 for the past several years. The battery is fine until it gets really cold. I mean close to freezing not severe cold. When it gets a little cold I will go out and the battery will be dead. Charge it up and everything is fine until the next little cold night. I know that there is probably something that is draining the battery but when I recharge the battery and try and find a battery drain parasite, I get nothing because the weather is better. Has anyone else found this to be their problem and know possibly what could be affected by the cold that would start a battery drain? Replaced the battery multiple times and get the same result. Thanks to all of you in the forum for your input and help.

 

One thought- you might be replacing the battery with new ones that do not have the required minimum number of cold cranking amps (CCAs). I am not sure what the LS 430 battery specs are but you can look that up and compare to what you have. Inspect and clean battery terminals and check alternator output too.

 

I don't now if this would help that problem, but with my car I finally had the dealer install a Lexus Deltran battery tender. It is set up so the plug comes out of the grill so all I have to do is plug the tender into it. I haven't had it long enough to know if this is going to avoid the problem with my car.

The parts guy at the dealer told me they had many of that type of tender in stock as the less driving during the pandemic was causing people battery problems.

 

after a month of driving I'm showing 41 miles per charge or 40 with AC. mpg on HV mode is 99.9