AirFanta 3Pro + DIY LiFePO4 battery backup runs over a week at 141 CFM

In a scenario combining a biological or nuclear threat with a power outage, a battery-powered air purifier becomes critical. The AirFanta 3Pro, a HEPA filter, is ideal for cleaning incoming air to maintain positive pressure. Paired with a 100Ah LiFePO4 battery (dischargeable to 80–100%), the system provides 141 CFM for over a week. Total cost: $188 for the battery components (battery, coulomb counter, fuse, connectors, charger) plus $164 for the purifier. This DIY approach costs $0.15/Wh, significantly cheaper than portable power supplies like the Anker SOLIX at $0.43/Wh. The LiFePO4 battery weighs just 24 lbs (vs. 57 lbs for AGM) and can be recharged via solar or grid when power returns. The main limitation is that it only powers 12V DC devices, not AC appliances. The coulomb counter tracks remaining capacity, and the fuse protects against shorts. While no off-the-shelf "battery box" exists for this specific use (marine battery boxes lack proper charge controllers), the DIY assembly is straightforward for those with basic wiring skills. This setup fills a niche for long-duration emergency filtration without relying on the grid.