ESP8266 Community Forum

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.

you're talking about the 'sparkfun thing dev' the normal thing doesn't have a usb serial converter.
Here's a post about the Thing and deep sleep https://openhomeautomation.net/esp8266-battery

again:
did you check it is going into deepsleep?
did you check the onewirebus is not going low in depsleep and drains the battery via the pull-ups?
is there any other "periphery" connected?
what arduino esp-core versions are you using?

my "weather-sensor" runs on one 1600mAh LiFePO cell for appr. one year with 15min intervals

It's going into deepsleep
I still need to change the onewire to parasitic mode
There's nothing else connected
I'm using Espressif 8266 version 2.2.3