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Lexus RX350 Battery Drain Problems

I realize I’m chiming in almost a decade later, but I’m noticing the same issue with my 2006 RX330 (SUV). The first time this happened, I’d left a charger in the lighter/outlet-thing. However, the previous owner said they’d done that before and never had any issues.

Most recently, due to the coronavirus pandemic, we’ve just kept it in the garage the whole time, and just take my wife’s car for grocery runs (different type of car). I went downstairs yesterday to start up the Lexus and get the fluids running, and found the battery next to dead. At first, it did the rapid clicking sound it makes when trying to turn over a car with a next-to-dead battery, but now, the horn won’t even sound & I have to lock/unlock it with the key.

No lights are on, no modules, nothing’s plugged in anywhere, and the keys are far away from the vehicle when not in use. There is a clicking sound coming from a box under the fuse box (under the hood). Also, the lights around the ignition, and the light in the side compartment, flash every second.

I’m neither an electrician nor mechanic, so much of what’s been said (between the drama) in the previous comments are like reading another language to me. I’m hoping that someone’s figured out what it is since the previous comments 8 years ago. Thanks.

Do you have a battery charger to recharge the battery?

Yeah, I just bought a lithium battery charger.
I also just learned what it is that keeps draining the battery. Turns out that because of tall the computers and stuff, the batter never completely shuts down, even when the car’s off. So to keep the battery from draining like this, I need to drive it at least once a week.

I’m not sure what a lithium battery charger is unless the charger is designed to charge lithium batteries. There are a number of things in todays cars that require constant power draw on the battery while the engine is off. Most current draws are under 50 milliamps while the car is parked and things have gone into the ‘sleep’ mode. You should be able to at to go at least several weeks without starting the engine if things are working correctly. You may want to have a shop check things out and see what the parasitic current drain is.

Did you mean lithium battery pack for jumping vehicles ?

Hey Cougar,
Sorry, a lithium batter charger is a new jump-starter, like a power bank or something, but to jump start a car. Anyway, I think you have a great idea there. My mechanic also said that with a lot of newer cars having so many computers on them, not everything turns off completely when the car’s off. So that would explain the power drain. Especially since this year & model definitely has a lot of computer stuff on it.

However, I am also going to take your advice on bringing it in to have it checked out, as well as get a new battery, assuming the lithium battery-thing I mentioned actually works.

Thanks for getting back to me. I was in freak-out mode when I originally typed up the question. I appreciate the quick feedback.


While the jump starter battery pack can help you get a engine started when the main battery is weak, it isn’t a replacement for a battery charger. When batteries are so low they can’t get the engine started the battery should be really be recharged using a charger. A drained battery puts extra strain on the alternator.