Right, I've tried my best to draw up a circuit diagram which will be clearer. Hopefully it's better than my last attempt.
Here's a link to the battery i'm using which has a datasheet on the page: REC22-12I - REC - VRLA - Cyclic Use - Industrial - Batteries
The Gearmotor C I'm using: https://www.robotshop.com/media/files/pdf2/016-rb-cyt-34.pdf
Gearmotor C driver (Adafruit DRV8871): https://cdn-shop.adafruit.com/product-files/3190/drv8871.pdf
5V step down voltage regulator: Pololu 5V, 2.5A Step-Down Voltage Regulator D24V25F5
I don't seem to be able to find the FC-03 speed sensor datasheet, nor one for the IBT-2 43A motor driver.
Let me know if there is anymore information I can give to help.
Many thanks,
Michael
