Hey, maybe one of y'all might know this.
I'm working on a super low power personal project, MSP430 based, that will hook up to a garage door opener's pushbutton circuit. My guesstimated average load current on it is under a microamp, and I'm thinking of powering it from a lithium coin cell.
I'm also looking at needing to sense whether the opener is hooked up to my board correctly. If so, it's +HV; if not it'll be -HV, where HV is in the 12-24V range. I figure megaohm resistor into a GPIO pin, let the ESD diodes clamp it, and there you go.
This works fine, except that it means that when things are hooked up correctly I'll be dumping some few microamps back into the battery; as I won't be burning it up as a load.
Yes, I've thought of pitching the battery entirely and just parasiting the power, and I'm still thinking about it, but there are issues there too. Likewise, I could add a zener diode clamp, but at these sorts of trivial currents repeatability could be an issue.
So what I'm wondering is, does know anything about what would happen over the long term (5-10 yr) with a lithium battery receiving a trickle of reverse current?