From a channel with just 12 subscribers, this build tackles a genuinely useful problem: keeping your router alive during power outages. Unlike a commercial UPS that wastes energy inverting DC to AC and back again, a DC-to-DC router UPS taps the battery directly, which is far more efficient for a device that internally runs on low-voltage DC anyway.

The build is likely to walk through the core sub-circuits you'd expect: a Li-ion or LiFePO4 cell pack, a TP4056 or similar charge controller with protection, a boost converter to step the ~3.7–12.6V pack voltage up to the router's required 9V or 12V, and an automatic changeover so the battery only takes the load when mains drops. That combination is a great teaching vehicle because each block — charging chemistry, over-discharge protection, DC-DC conversion, and load switching — is a fundamental building block you'll reuse in dozens of other projects.

Adjustable output (5V–12V) means it's not just a router accessory but a general-purpose backup bench supply for cameras, modems, small SBCs, or DC LED strips. Worth watching to see how a small creator wires the modules together and, importantly, what protections they include (or forget) — a great critical-viewing exercise for anyone learning power electronics.