2nd Gen Non-Engine/Transmission Battery question

[tony_h]

Well, the heat finally killed my batteries. They were questionable but 7 straight days of 105+ finally sealed the coffin on them.



Anyway, on Sunday I pulled the batteries. Monday I went to work in the wife's minivan (that hurt) and got the batteries after work at a local battery shop. I put the batteries back in on Monday about 24 hours after I took them out.



I know this sounds like a ridiculous question, but I really want to know. I didn't lose any of the radio station presets (stock AM. FM/cassette/CD player) but I had to reset the clock on the radio. Furthermore, my trip meter was reset to 0. 0. Why does some of the information get saved and others don't? Where is this information saved or how is power kept to it?

 

[K5IP]

The radio has filter capacitors which store some energy when the battery is removed. The clock keeps time via a time based crystal controlled oscillator which requires a fair amount of power. When you removed the cables the clock oscillator ran for a few seconds, and then stopped. When it stopped it quit drawing power leaving enough charge (very small) for the RAM devices (presets) to remain active. They too would have failed eventually. The trip meter did not stay alive because it did not have the capacitive back up the radio had.

Rog