My previous Lexus was a 2013 GS and always started first time, every time. During about 12 years of ownership, I replaced the battery probably twice. The only time I needed a jump was if I left a door open or lights on.

I traded to a 2025 RX450h+, plug in hybrid. Nice vehicle…comfortable, great ride, plenty of power for me, and safety features galore. BUT…

One day, I had just unplugged from my L2 charger-topped it off. Got in to start the car, and all I got was a few seconds of groan…followed by dead as a doorknob! The only good news was that I was in my garage. Lexus road service was quoting 3 hr, later updated to 1.5 hr. Called my dealer, and one of their techs stopped over on his way home - this was Saturday on a holiday weekend . He got me going with a portable jump starter, and I went to the dealer the next day. The bottom line was that they replaced my 12 V battery. I spoke to the service manager and asked what happened, and how could we stop this from happening in the future. She explained about the role of the 12 V battery as opposed to the hybrid battery and it turns out that all the little bells and whistles in the car keep pulling current, even while the car is parked. That explained why the 12 V battery was dead, while the hybrid battery was fully charged, and yet the car wouldn’t start. She said the battery was bad and was replaced under warranty.

I said that’s great, but what can I do to prevent this from happening in the future? It didn’t inspire much confidence when she basically told me that I needed to drive my car more often.

So here I am getting ready for a trip out of town where my car is going to sit in my garage for the better part of two weeks, and frankly, I expect that 12 V battery to be all drained by the time I get home. Expecting that, I bought one of those portable jumpstart batteries based on recommendations in this forum, so I can at least get myself going, if that turns out to be the case. I’ve been told the one way to prevent this from happening is to get a trickle charger and put the car battery on it. I don’t know the details of where I should hook that up to the car. I got it came out to start my car connected under the hood to jump, but I understand the battery itself is under the floor in the back of the car. Can anybody point me to some directions on how to hook that up?

The L2 charger and regular outlets are in the garage so where to plug it in shouldn’t be a problem, but I wanna make absolutely sure that I’m connecting in the right place, for fear of damaging something in the car.

The best solution would be to be able to turn off all those functions that are running in the background and draining the battery. For example, I don’t need the receiver to be looking for the key fobs to detect their presence. I certainly don’t need ANY telematics of the car connecting to any external servers - my single biggest beef with the car, easily. I don’t need the stolen car tracking, since the car is in my garage.

I would like to just disconnect the battery, buy I suspect Lexus doesn’t want me to control MY car, and there would be a ton of things to reset.

If Lexus really cared about the owner, there would be a simple switch that would turn off the vampire drains, and some mechanism to let the smartphone know that the 12 volt battery is getting low.

Any suggestions? TIA

 

https://www.clublexus.com/forums/rx-...d-threads.html Happy reading

 

This issue is discussed Every.Single.Day here.

Scroll down.

 

If I were you, for longer trips away and the car is going to sit, I'd just hook up a trickle charger such as this one: https://www.homedepot.com/p/Schumach...e=en-US&fp=ggl I have several trickle chargers. One for a lawn tractor, another for an electric start mower, and another for a classic car.

I use the one's that have the "clip on" or "alligator" style attachments and not the one's that have to be bolted on. They supply low amp charging to the battery and when the battery is fully charged they will monitor that. Should the charge decrease, they will kick back on and recharge.

I'd hook that right to the battery. The battery is in your "trunk" area to the right of the spare tire and towards the rear bumper. There's a plastic shroud that covers the battery. Just reach over and pop off that plastic cover.

 

I hadn’t visited the forum in several weeks…other fires to tend to.
I didn’t have the time to do the full ClubLexus catchup…my apologies for not doing that before posting.

 

I ordered a similar charger (NOKO GENIUS 1) from Amazon…should be here tomorrow. The car will be in my enclosed garage. After I get the shroud off the battery, and connect alligator clamps onto the battery terminals, and plug into the ac outlet, can I just leave the trunk hatch open ? Will that create a problem? I’d rather not close the hatch on the AC line cord.

 

Will do! Thanks

 

Leaving the rear hatch open should NOT cause an issue. Our cargo area lights turn off after about 5 - 10 minutes.

But closing the hatch onto the typical smallish wires of a battery maintainer should not concern you. We do that routinely on our sports cars during their 'winter hibernation', with no issues.

 

When I’ve done the occasional trickle charge on our 2025 RX350h, I close the rear hatch. I’m not worried about the cable getting pinch between those big rubber gaskets.

 

You should be fine leaving the hatch open. The trickle charger should more than make up for any small parasitic drain. Leaving the hatch open (as others have said) will not cause the interior lights to stay on constantly.