Ours has 150k on it now 2013 as well. I actually think the hybrid battery is going. I don't know if you guys remember when I bought the car several years ago with 80 something k, that it only processed as a fair rating on the Dr Prius app. But hey, it still lasted another 70k. I don't like using Dr. Prius because of the strain on the battery lol.

 

My 12 volt Auxiliary Battery (for Audio, NAV, Lighting) failed the load test today (12-8-2025) when I was having my 2018 GS 450h serviced.

It was the original 12 Volt battery installed when the car was built in 2017 so it was~8 years old. I had it load tested in 2021 and it tested good, but 8 years is about all one can expect it to last - especially with the car having been in storage for about 3 years from 2018 to 2021 when I bought it with just 5k miles on it.

Part # 28800-31411 $738.44 + $75.22 Labor = $813.66

 

Dealer says 12v battery needs replaced. I guess the aftermarket ones, just don't last like the Panasonic. My original one lasted 11 years! Aftermarket....one year, go figure. It does have a 3 year replacement warranty, but I don't think I will try it again.

 

It's my understanding the 12 volt PN:28800-31411 auxiliary battery (used for lighting, audio, HVAC, NAV, etc.) in the GS450h requires it to be designed simulating a deep charge type battery. A typical 12 volt battery is not like that. Also, the 12 volt PN:28800-31411 auxiliary battery for the GS450h requires it to be vented with a vent hose port in the top side of the case, making it rather special in more ways than one.

Here is a picture of my new Lexus PN:28800-31411 Panasonic 12 volt auxiliary battery located in its left side compartment in the trunk.

 

They only sent a video, so I captured this
It is only 1 year old battery and it is a AGM deep cycle.

 

For whatever reason (design/plate configuration, etc.) a sulfated battery is a weakened battery that cannot be trusted.

Battery sulfation degrades lead-acid batteries by forming hard lead sulfate crystals on the plates, reducing their surface area, increasing internal resistance, and crippling the battery's ability to hold charge and deliver power, leading to premature failure, slow cranking, and shorter life.

It's time for a proper 12 volt auxiliary battery designed for how the GS 450h uses the 12 volt for auxiliary to power (all lighting, audio, HVAC, Navigation, power seat, seat heating/cooling, power rear shade, etc.) - that also has a venting port....

 

When I had the Infiniti Q50 hybrid it came with standard flooded lead acid battery. The battery started to play up at about 4 year mark in winter time (just when the warranty ran out). I notice things like taking longer to read the TPMS, once the door lock will unlock and lock again or takes a couple of presses to lock the car.
The Q50 hybrid was probably harder on 12v battery because it can run in hybrid mode up to 140km/h or 87mph before the ICE kicks in and on a flat road the Q50 can run on hybrid only mode for about 4km or 2.5miles.

I change it to a battery design for STOP / START vehicles and had no issues even when we sold the car at the 10 year mark. The stop/start batteries have thicker plates and design to cope with repeated starts and electrical demands compared to standard flooded lead acid batteries.

Funny though, I notice that the Stop / Start batteries tends to have less warranty (about 2 years private use or 1 year for commercial use) compared to the premium lead acid batteries.

I now budget for a change of battery at about every 4-5 years as I don't want to get my wife stranded when she uses the car. I feel its pretty cheap insurance.

 

I told my son to pull the trigger. $709 we got a better price than you @bclexus lol. 2 day wait to order and charge one.

 

Yeah, mine was $29 more at $738 vs yours at $709 - (I say 'big deal' lol) but I didn't have to wait to get it because my local Lexus dealership has the latest (and supposedly improved) replacement 12 volt auxiliary battery in their stock.

Did you know your son could have purchased the Lexus PN:28800-31410 12 volt auxiliary battery for the GS 450h for only $533 HERE and saved $176 vs. paying $709, so there's that @spineman lol.

I personally wanted the latest replacement battery and did not want to wait for a shipment and replace the battery myself, because there is a procedure the Lexus tech must follow to shut down various loads before replacing the battery and I didn't want to chance bricking anything.

Lastly, I don't mind paying a premium for the latest replacement Lexus battery and I don't mind paying the labor to have a Lexus tech replace it for me... Additionally, I don't like using an aftermarket battery (like has failed in your son's car) when the carmaker requires this particular battery be built in a specialized way - I'll take the Lexus 12 volt auxiliary battery made by Panasonic for Lexus, lol!

Did you know the (above referenced) PN: 28800-31410 has been replaced with the PN: 28800-31411? Do you even know what the part number will be of the battery that you're waiting on (even though you may have ordered the PN: 28800-31411, lol?