Interesting feedback. Was the 9V battery plugged in to the power port while you were waiting an hour for the modules “went to sleep”? It sounds like the 9V battery got cooked by the 12VDC battery. I’d expect that if they were both connected for more than a moment any one time, but I think the 12VDC battery is supposed to be disconected immediately upon plugging the 9V battery in, and then I think the 9V battery will on;t save the memory for 1/2 hour.
It didn’t save the radio presets
It didn’t save the clock
It also fried the airbag control module
That was a few years ago, though.
Nevertheless, I’m not going to let it happen to me again.
I now write down my radio presets before I disconnect my battery
In the past, I used the type of memory saver that has long leads with alligator clamps and connected it to an old car battery, but I’ve never tried the type with a 9V battery.
Thankfully, the only noticeable things that I lose when I disconnect the battery are the clock setting and the trip data values (avg. MPG, etc.), as the radio reads and matches the VIN from the car.
Thanks guys. I’ve seen these things in the marketplace and wondered, primariarily since they’re only 9V. It would make some sense if it were connected after the 12VDC were disconnected and then disconnected before reconnecting the 12VDC, but you’d lose your memory by then anyway.
@thesamemountainbike: It sounds like the 9V battery got cooked by the 12VDC battery
The 9V battery was protected by a diode that prevented current from the car battery from flowing back. I had to do it that way as opening the car door to plug in the “memory saver” activated the dome light, dashboard display and who knows what else. This was all checked with the multimeter when I plugged it in, and there was only 9V across the alkaline battery, so I’m without an explanation. You’re right, without a diode the car battery would have fried the 9V almost instantly as there would be nothing to limit the current.