New Battery but settings were kept???

[Matthew]

Just bought a new battery for our 2001 Impala on the 3rd. Battery replacement was a pain in the ass to say the least and i wasnt looking forward to reprogramming everything. After the battery install was completed to my amazment the alarm key fob still worked the HomeLink was still Programmed to our Garage Door and the Radio Station presets were still in place how the hell is this possible? all i had to do was set the clock!

Topic

[Matt]

Probably capacitors built into the system to do just what it did..

[dave]

solid state microchips do not need to be kept under power to retain their memory. :blink:

[Matthew]

then how come the Radio Presets retained but the clock didnt?

[EricTheCarGuy]

Things like that are usually the result of keep alive memory which used capacitors to store enough electricity to keep the memory for a few min even if power is disconnected.

That’s the best explanation I can come up with at the moment however.

[twiggy]

This is why I posted a long time ago urging to excercise caution when shorting the disconnected terminals together to reset the electronics. If it’s true that the caps are holding the voltage, this would result in a huge current spike also causing a huge voltage spike. Better to let the dome light bleed this voltage off if you want to perform a reset.

[Matthew]

[quote=”twiggy02919″ post=56069]This is why I posted a long time ago urging to excercise caution when shorting the disconnected terminals together to reset the electronics. If it’s true that the caps are holding the voltage, this would result in a huge current spike also causing a huge voltage spike. Better to let the dome light bleed this voltage off if you want to perform a reset.[/quote]

The dome light would work with no battery just off the caps alone? i dont want to reset the electronics i was just surprised no car ive ever replaced the battery on ever kept its settings. and by the way it took about 2 hours to install the battery it was a bitch getting the bar out of the way it was only a few minutes ACTUALLY installing it. question is can i use say a 9V battery hooked to the termals of my daewoo to maintain its settings as i change the battery?

[twiggy]

[quote=”LeoTheLion89″ post=56075][quote=”twiggy02919″ post=56069]This is why I posted a long time ago urging to excercise caution when shorting the disconnected terminals together to reset the electronics. If it’s true that the caps are holding the voltage, this would result in a huge current spike also causing a huge voltage spike. Better to let the dome light bleed this voltage off if you want to perform a reset.[/quote]

The dome light would work with no battery just off the caps alone? i dont want to reset the electronics i was just surprised no car ive ever replaced the battery on ever kept its settings. and by the way it took about 2 hours to install the battery it was a bitch getting the bar out of the way it was only a few minutes ACTUALLY installing it. question is can i use say a 9V battery hooked to the termals of my daewoo to maintain its settings as i change the battery?[/quote]

You wouldn’t see the dome light work as it would quickly (but controlled) discharge the caps. If you car requires you to turn the ignition key to the ON position to use the memory saver, I would not use it. While you are connecting/disconnecting the battery it is best to have as many thing off as possible as voltage spikes are created during the change. No matter how careful you are, there are voltage spikes and “chattering” going on. I’ve observed this on a lab scope many times. The waveforms would make you nervous.

[Author]

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