SenneS wrote:It hasn't have a usb serial so that's no problem.
What SparkFun Thing do you have, since the one I know has a USB-UART convertor on-board.
SenneS wrote:But still if you read about the esp8266 and deepsleep you find that people can power it for weeks when I only get to power it for under a week.
(Most of) these projects don't use a development board like the SparkFun Thing, NodeMCU or Wemos, but a single ESP module (like an ESP-01 or ESP-12) combined with it a low external component count (like drivers for I/O) and an optimized low-loss DC-DC convertor.
When you're new, don't start with a separate ESP (ESP-01 to ESP-14) module.
Get yourself a proper development board: NodeMCU - WeMos D1 - WeMos (UNO form factor) - Witty Board
ESP power requirements are 3.3V±10%@350mA
The ESP8266 IS NOT 5V tolerant on ANY pin (see item 5.14 on page 25 of the FAQ)