I measured the current from the battery during deep sleep.

W/ red LED the current was 831 uA.
The red LED consumes (3.3 V - 1.85 V)/ 2 kOhm = 725 uA.
Cutting off the red LED would result in 106 uA.
Is it possible to reduce this current further?

The red LED should be switched off to get minimum current consumption during deep sleep.
A solder bridge would be helpful.
At default initialization I get the following value reading the TOUT:

E (798844) tsens: Do not configure the temp sensor when it's running!
E (798844) tsens: Temperature sensor is already running or not be configured
ADC analog value = 2954
ADC millivolts value = 1407
Core temperature = 44.6 °C

I expect 1/2 VBAT, also about 1900 mV.
Why I get the two messages tsens: ...

This is my program:

void setup() 
{
  Serial.begin(115200);
  
  analogReadResolution(12);
  analogSetAttenuation(ADC_11db); 
}

void loop() 
{
  // read the analog / millivolts value for GPIO2:
  int analogValue = analogRead(2);
  int analogVolts = analogReadMilliVolts(2);
  float temp = temperatureRead();
  
  // print out the values you read:
  Serial.printf("ADC analog value = %d\n",analogValue);
  Serial.printf("ADC millivolts value = %d\n",analogVolts);
  Serial.printf("Core temperature = %3.1f °C\n\n", temp);
  
  delay(2000);  // delay in between reads for clear read from serial
}

I get no valid data from DS18B20 connected to the OneWire bus (IO21). According to the schematic, there should be a pullup resistor.
I used the ds18b20.h from https://github.com/Xinyuan-LilyGO/LilyGo-HiGrow/tree/master/src.

Here is my application of TTGO T-Higrow Sensor (my post is in the German language - if required, use Google to translate)

https://ckarduino.wordpress.com/2021/11/16/messung-von-umgebungsbedingungen-fur-pflanzen-mit-lilygottgo-t-higrow-sensor/

There is no battery inside, but a loader circuit.
Must the battery be connected to VBAT pin? Which battery type is preferred?

Today I got the device and tried the Hellow World example.
I got the following compiler error:

Arduino: 1.8.15 (Windows 10), Board: "ESP32 Dev Module, Disabled, Default 4MB with spiffs (1.2MB APP/1.5MB SPIFFS), 240MHz (WiFi/BT), QIO, 80MHz, 4MB (32Mb), 921600, Core 1, Core 1, None"

D:\ArduinoSketches\LiLyGoMiniePaper_HW\LiLyGoMiniePaper_HW.ino: In function 'void setup()':

LiLyGoMiniePaper_HW:75:13: error: 'POWER_ENABLE' was not declared in this scope

 pinMode(POWER_ENABLE, OUTPUT);

         ^~~~~~~~~~~~

D:\ArduinoSketches\LiLyGoMiniePaper_HW\LiLyGoMiniePaper_HW.ino:75:13: note: suggested alternative: 'IBREAKENABLE'

 pinMode(POWER_ENABLE, OUTPUT);

         ^~~~~~~~~~~~

         IBREAKENABLE

exit status 1

'POWER_ENABLE' was not declared in this scope

I could not find the declaration of POWER_ENABLE anywhere.
Commenting on both instructions in setup() there are no compiler errors. But I get a cyclic reboot.

Why do I have to select ESP32 Dev Module and not ESP32 Pico?