Teensy 3.x Feather Adapter : ID 3200 : $5.95 : Adafruit Industries, Unique & fun DIY electronics and kits
PJRC (Teensy) Forum
3.7v-14.8v 2a Mini Wireless Remote Control Switch Board Low Power Lithium Battery Power Control Module - Inverters & Converters - AliExpress
Using External Power and USB with the Teensy USB development board
Teensy 4.1 Power Usage - YouTube
Teensy® 4.1
Teensy 4.0 Brings 600 MHz Cortex-M7 to the Arduino World - Hackster.io
Using External Power and USB with the Teensy USB development board
arduino - Strange problem with Teensy 4.0 connected to external power only running code when serial connection is introduced - Electrical Engineering Stack Exchange
Teensy 3.2
New Teensy 3.6, power and charging circuitry | Details | Hackaday.io
Teensy 4.0 Brings 600 MHz Cortex-M7 to the Arduino World - Hackster.io