Battery is almost 5 years old.
When cold, I see 11.2 to 11.8 volts.
After driving for a while it gets to 12.2 volts
For the Lexus LS 430, you can see the battery voltage in the hidden/secret Service Menu, Display Check, Vehicle Signal Check:


Battery Voltage in the Lexus Service Menu

 

My car battery finally died yesterday. Car would not crank, just a click. No clear indication in the Lexus diagnostics screen even a couple of weeks ago that the battery was weak: it still read over 12V when warm.

It was a 3-year AAA battery that lasted almost 5.5 years, so can't complain there. I had it replaced by AAA with similar (130 bucks, installed: size 24F, 700+ CCA, I think). The AAA guy found the charging system to be OK but the old battery only registered 9.7V and less than 100 CCA on his measuring instrument.

The first sign I think that this car battery in the Lexus LS430 is weak is when your car won't arm properly or at times using the key FOB. I replaced the key FOB battery and sometimes still had that problem. No other electrical indication other than that: all else is fine until stops starting the car.

 

05 LS430. Tried every button and option on my display and can NOT find anything like you posted "Service menu/Display Check/Vehicle signal check. Please advise further. Thank you.

 

Check the voltage at the battery not with a scan tool.

 

no point in trying to squeeze every mile out of the battery, it will die on you at the worst possible place and time. Not worth it

 

Static voltage means little. The real test is to put a serious load on the battery and check the voltage then. For example, turn on your high-beam headlights, then see how much they dim when cranking. Or at least this worked with traditional incandescents and halogens.

As for going to the very end, if you're a miser then just carry one of those tiny battery packs in the trunk. It will take you a couple of minutes to hook it up but your car WILL crank.

 

all goes back to v=ir. r increases over time. I fought it like many for years, but I finally broke down and spent $30 on a load tester. I get that not everyone wants to spend $30 on it, but it's the difference between guessing and knowing. Example my mom was on the fence about a new battery but I said I'll get it for you $75 at Costco, last Thanksgiving. tested hers and it had 240 CCA. This winter it likely would have been fine, but a normal winter in CT should have left her stranded....and you can get batteries tested for free as well.

Someone here said they get a new battery free at Costco regardless every 2 years no questions asked. Maybe Costco should invest $30 or $10 to them in a load tester, with about 800 locations it's not even ten grand! This way they can make an informed decision on whether to replace under warranty or if the battery is still good. I get they take anything and everything back, we returned unopened Pull Ups that I discovered in the basement. Some have even returned soiled diapers which is kinda sick.