Wake up from deep sleep on external power?

Let’s say I have en electron (asset tracker) that’s running off of external power (car battery) and has a small LiPo standby battery (100mah).

I’m putting the electron into deep sleep when the external (car battery) power is shut off. Is there a reasonable way to wake up the electron from deep sleep when the external power kicks back on?

I’m using a standby battery so I can publish an event after the vehicle is turned off. Obviously, if the standby battery is depleted during deep sleep, powering externally will reset the electron… but how can I handle it if the standby battery doesn’t die during sleep?

TIA~

How are you detecting that the power from car battery is off ? How are the car battery and the LiPo connected to your Electron?

To wake up the Electron, you would want a rising edge on the WKP pin. The question is how to get a 3-5 volt level from your 12 volt battery. Check out this answer on StackExchange for some ideas on how to do that.

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How are you detecting that the power from car battery is off ? How are the car battery and the LiPo connected to your Electron?

Car Battery -> Fuse -> Buck Step Down to 5V -> Electron, powered through Vin energized by “accessory” driven automotive relay. I also have a 100mah LiPo connected via the JST connector.

So… can I just run a “jumper” from Vin to the WKP pin, or am I misunderstanding how that mechanism works?