9V battery 'settings saver?'


Expedition Leader
Not specifically an expo question, but you guys are the biggest bunch of wrench-turners I know...

Short story: I had to do some battery work on one of my vehicles today (a 2005 Toyota Sienna). When I was in the ‘battery maintenance stuff’ section of the parts store I saw a $5 gadget that had a 9V battery on one end, and a cigarette lighter plug on the other. Advertised as a device to keep from loosing your radio station presets, ECM memory, etc. when you disconnect your vehicle battery. I didn’t buy it, but now think I should have. More in ‘Long story,’ below.

Have any of you used this thing? My initial thought is that a 9V transistor battery probably won’t work for maintaining the memory in 12V devices, but maybe?

Long story: After disconnecting and reconnecting the battery, sure enough, I lost all the radio pre-sets. I expected that. Have to reset the clock. Also expected that. However, I wasn’t expecting to loose some aux functions that I’m guessing are controlled by the ECM.

The electric windows still work, but the ‘auto-up/auto-down’ functionality on the drivers window and the sunroof no longer work. i.e. Before, if you pushed lightly on the ‘window down’ button, the window would go down until you released the button, but if you pushed a little harder you would feel a click and the window would roll all the way down. Now it doesn’t matter how hard you push on the button, the window stops moving when you release the button. Same with the electric sunroof.

All in all pretty minor, I know, but if I’m right and this is ECM related, it makes me wonder what I could loose next time I disconnect the battery, and maybe that little $5 gizmo would be a good investment.

Now I’ll probably have to pay the mechanic $75 now to ‘reset’ the ECM. Grumble grumble grumble.


The 9V memory saver is reputed to work, although the cigarette socket you use has to be a constant hot outlet, not one of the newer auxiliary power jacks, which are keyed to the ignition. The amount of voltage needed to save memory in the computer is far less than 12V, although I don't know exactly what it is, probably somewhere around 3V.

I have always used another car battery and jumpers to maintain power when pulling the battery, but that is a hassle at the least, and if you need to work on something electrical and need to disconnect power, I suppose using a jumped battery would defeat the purpose.

The learned major sensor inputs should reestablish themselves within a few miles of driving, and all of the adaptive fine tuning that the ECM does over the miles should be completely reestablished within 100 miles, if not before.

Can't say why the windows won't work correctly. I would not think the express down features were not ECM controlled, but I suppose they could be. You could check with a dealer.


I'm not against technology, but I hate this junk about normal maintenance (replacing a battery, getting a jumpstart) ruining basic functions like a radio, power windows, etc.

I'm replacing Joni's mom's (late model cadillac) car radio because she got a jumpstart and it got fried... later she read the owners manual and it specifically says not to jumpstart for that reason. WTFritos?


I have a battery tender with a aux. power adapter (cig. lighter) that does the same thing, but also charges my camper/4 wheeler battery. It's made by vector and it was sold under the Black and Decker name at wally-world.
Works great in my opinion and for around $18, not to shabby.


Expedition Leader
Just as an update, the 'auto' switch for the driver's window has started working agian, but still not sunroof switch.


Expedition Leader
If the radio and the power outlet are on the same circuit (same side of the ignition switch), than the 9v gadget should work, as far as the radio's settings go. I can plug a portable 12v battery pack into my 12v outlet (using a male-to-male cord) and listen to the radio without using the ignition key.

The owner's manual may have information on restoring settings such as the window controls (e.g. turn the ignition on and off 3.75 times).