Make sure the replacement battery you get is an AGM type. Lexus would not have spent the extra money to put that type in originally if the car didn't need it. That's what the dealeships would put in.

 

Replace with the correct optima. I haven't even thought of replacing the battery again since installing one. I live in a cold climate, so reliable batteries are a bit of a necessity and all the years I've been using them, optima hasn't let me down.

 

Well, Optimas are for hybrids, I see no indications Op has hybrid.
What I am saying, if you had 3 dead batteries in 75 000 miles, you have issue. They should last much more than that, especially the OEM one. My TCH OEM Panasonic, from 2006, it still working.
Hence, you have something that shortens battery life drastically. Likely a parasite drain or higher than spec resistance somewhere, causing premature battery failure. Though, knowing how sensitive Lexus is to any non spec electrical parameters, you'd have had a light in the dash by now..
Whoever mentioned corroded battery clamps and cable connections - as you have that too, on cables, is right. Corrosion results in high resistance and kills battery. Also, battery is constantly undercharged. Your alternator may be doing sub par job, not charging battery enough. Just enough not to throw a code yet... Combination of those factors.. Loose belt, for example...
You need a good indy electrician to scope all this.

 

I do agree with what you're saying. Those are definitely things to look into and consider. I just want to say that in 2013 Lexus switched to AGM type batteries in the standard rx350. There are regular batteries and then there are AGM type batteries. Most people will just get the standard battery as those are cheaper. There are different AGM batteries available from all brands, not just optima. Lexus must have realized these cars needed the hevy-duty AGM type or else why would they spend the extra money on it when they're looking to cut costs wherever they can.
What I wonder is if people just keep replacing their battery with a standard battery and that's why it only lasts a few years? Then they take it to dealer and they install a more expensive AGM type battery and "fix it".

 

 

Invest in a battery tender or if the vehicle is kept outside a solar battery maintainer. I use a solar maintainer on an old Honda and it has made a huge difference in keeping the battery alive and charged. I no longer have to hook my charger up every few weeks. It also taught me how fast a battery can drain when a vehicle is not being driven!

 

There are reasonably priced battery tenders nowadays, they are solid state too. They are about $50 but well worth the investment. The minute you plug it in (they come with these connectors that are installed in the terminal and you just plug and unplug). When you plug it it tells you how much the charge is and then it will trickle charge it up to 100% and will switch over to maintain mode. My 2 garaged cars have different age of batteries and as such it discharges at different rates. If your car is not a daily driver, it will need a battery maintainer.

 

 

I have a question for you all. My wife has an RX350 that is keot in the garage. It is not heated but seldom gets below 40F. It is 3 years old with 39K on the odo,. Lately when we start the car the engine turns over but it sounds like the battery is weak. It does this only in the morning and will do fine the rest of the day. I put a meter on it this morning and it read 12.5V. Seems early for the battery to give up and I do maintain the battery lever, The car has all sorts of electronics and maybe this is normal life for a battery in this vehicle. Just curious to see what you all think.
Russ

 

Not at all unusual for OEM batteries to begin fading away at three years of age these days. Modern vehicles are essentially rolling computers that demand high levels of power to properly function without being stressed and causing problems. Once cold temps show up for the season, marginal batteries really struggle. 12.5 volts is indeed marginal.

 

12.5 Volts is indeed marginal. Especially if it is not under load.

 

Turn on the headlights and recheck. Also try to start while checking. Have a load test ran at Walmart or any parts supply house.

 

Given the age and mileage the battery could be on it's way out. Most non-performance batteries I've seen/used have 3-year warranties, and many 5-year warranties work on a prorated schedule where the full replacement is no longer given after a year.

As already stated, just testing voltage really does not tell you that much. Take it to a parts store and have them do a proper load test on the thing (which is usually free.)

 

Thanks for the replies and advice. It's scheduled to go in for service on Thursday. Should I let Lexus install a new battery or do it myself. Any recommendations as to brand?

 

If you are handy, do it yourself and saved a few bucks. Go to Costco and get your battery. Good luck.