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I have a generic ESP 8266 wifi module board. The voltage ratings suggest 5 volts at the power micro-usb port which is internally dropped to 3.3 volts. Now there are direct 3.3 v header rails. Now can I power this rail directly from a Li ion battery (18560) whose voltage ratings are 3.6-4.2 volts ?

Saikat Banerjee
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  • What does the datasheet say? "Suggest" is pretty vague. – vir Mar 30 '24 at 01:34
  • Will this solution help ? https://electronics.stackexchange.com/questions/403112/can-i-use-series-diode-to-drop-voltage-from-lithium-ion-battery-to-esp8266?rq=1 – Saikat Banerjee Mar 30 '24 at 02:00

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No. The max battery voltage exceeds the limits for 3.3V logic supplies. You could add an LDO regulator in-line to prevent that.

Related: Regulated 3.3V from a Lithium-ion (or LiPo) battery

hacktastical
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You have a module. It presumably includes an LDO regulator to drop 5V to 3.3V.

To use it with less voltage you'd have to look at the datasheet of the regulator and see if it is up to the task. The radio current can be pretty high when transmitting (100 or 200mA, if memory serves) and you'd like the dropout voltage differential to be less than 300mV at those current levels.

For example, the SPX3819 used in some modules would be more-or-less acceptable (not guaranteed, but typically it should work at minimum battery voltage), but an AMS1117 would not.

Spehro Pefhany
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