ESP32 Forum

I've created an phone app that connects to a Bluetooth LE ESP32-S3 and power sensor. I'm using it to remotely monitor the voltage of my car battery via BLE. The ESP32-S3 and sensor are powered by the 12V car battery via an IC voltage regulator. I'd like to minimize the parasitic drain on the battery whenever I'm not monitoring the voltage. Since the WiFi/Bluetooth radio is turned off in Deep Sleep Mode, I'm suspecting the only option I have is to set the Deep Sleep Mode on a timer. That would mean that whenever I scan for the ESP32-S3, I'd have to wait for the timing cycle in which the radio is turned on. Am I understanding this correctly, or is there a better way to minimize the parasitic drain while I'm not monitoring the battery voltage?

Yes, the RF is a major power drain, so you'll have to turn it off to reduce consumption. On a C3, modem sleep reduces the system's consumption by 'only' ~50%, but you can try what it does on an S3.
Light sleep is probably a good alternative because the wake up time is much shorter, i.e. less power wasted for booting the chip every time.
You can also check if the S3 supports an external 32.768kHz crystal as the sleep clock for BLE which should reduce consumption of BLE during light sleep.

Also check the quiescent current of your voltage regulator. Some may draw 10mA or more even without load, making extensive power saving down stream moot.