I am working on a project using a XIAO-ESP32S3. I am using two 18650 lithium rechargeable batteries to power the ESP. I am recharging the batteries with a 650mAh solar panel. I was wondering which input would be better to use, the 5vdc or the 3.3vdc.
The voltage of the 18650 is 4.2vdc fully charged to 3vdc at the low end of usefulness. Since the 3.3vdc pin will only work with 3.3vdc I would have to use a 3.3vdc voltage regulator to reduce the battery voltage to 3.3vdc. Once the battery dropped below 3.3vdc the unit would stop functioning.
If ,on the other hand, I used a Polulo boost regulator to increase the battery voltage to 5vdc and used the 5-12vdc input pin with the internal 3.3vdc regulator I would provably have a longer battery life because the boost can work with very low input voltage.
I can set the low end of the 18650’s charge before I start recharging with the solar panel so th 3.3vdc would not be reached. But this may decrease the time between charges.
Boosting voltage just to reduce it seems less efficient but if the low end of the charge occurs at the beginning of the night and then a cloudy day the unit may go below the minimum 3.3vdc needed by the 3.3vdc input thus causing the unit to stop functioning.
I will be using deep sleep mode for the ESP every 15 minutes. Then the ESP will wake up to check the battery strength and start charging if necessary. After 8-15 minute cycles the ESP will wake up to check various sensors, connect to the wifi and send data to a MQTT broker. In certain instances the ESP will wake every 2.5 minutes to check sensor reading and send data for a total of one hour.
I hope this isn’t a nuisance question.
I am asking for anyone/everyone’s input on this. Which one would you use and why.