OK, so my car battery died a very quick death. Turns out the cells were dry.
So I bought a replacment, which leads to this question:
Can I just swap out the battery without having to go through any major system resets?
I did a quick thread search here and did not find the info...so a point in that direction may be sufficient.
Thanks a bunch!

 

You could connect a 12 volt charger to the battery leads and leave them on when you swap the battery. I think some things get reset after the leads are off for 30 secs but not sure on specifics ...telling you more than I know at this point.. Hopefully someone with some expertise will chime in.

 

I've disconnected my battery for various durations between 5 minutes and 4 hours, my seat position and steering wheel memories are still good. The auto-open/close moonroof button will only work after initialization, by sliding the moonroof all the way back and then closing it fully.

The Lexus manuals instruct you to initialize the power seat ECUs after disconnecting and reconnecting the battery. This is performed by sliding the seat all the way forward, then recline the seatback forwards fully, and fully raise the seat cushion and headrest. Then slide the seat fully rearward, fully recline the seatback rearward, and fully lower the seat cushion and headrest.

Sometimes the power window ECUs need to be initialized as well. This can be done by rolling each window all the way down and then back up (not using the auto-open/close function).

I don't use the radio so I don't know if those settings save - probably not though.

The Nav system "Previous Destinations" memory is kept if you don't disconnect for too long. The Nav system's "Marked Points" appear to be kept regardless of disconnect time.

Note that the Engine Start mode (usually 75 amps) on a battery charger is only to be used when a battery is connected. Without a battery, it can cause damage to the vehicle's electrical system.

 

if it's been dead say overnight, plan on a lot of resets, including all nav points. although, it memory serves correct, i don't believe i've ever had to reset anything associated w/ memory seats/mirrors/steering wheel. i upgraded my cell phone to one that can push the phonebook to the car after my last battery replacement, so i don't know if you lose your phonebook.

 

First, thanks for all the feedback!
The replacement took all of about 15 minutes, with the only curveball being the clips that hold the positive terminals to the side of the battery compartment. It is pretty obvious how to remove them once you can get a good look.

A note of caution, do not overtighten the top nuts to the rods that secure the battery down to the base (which is made of plastic). One side of mine was cracked (apparently from a previous replacement).

A quick start and it appears all settings are saved...will let you know if I find any major distractions as the car gets driven.

EnJOY your day!