36W UPS for router or other low powered devices 3x21700

This is my project for a 36W UPS designed for use with a router or other low-powered devices.

• 36W 3S Ups module
• Heatsink 50x25x10mm
• Switch
• DC connector 5.5x2.1mm (Type F)
• Zip tie optionally for cable management
• DCDC down converter 3.3, 5, 9V. Optionally: If you need less than 12V
• BMS for 3S Litium batteries
• Silicone Rubber Sealant for main board fixation
• DC Power Plug:
• • Male (5.5 x 2.1mm) OR (5.5 x 2.5mm)
• • Male (3.5 x 1.3mm)
• 3 x 21700 Li-ion Batteries
• Staff for battery welding or someone who can do it for you.
• Battery indicator