A follower recommended a so-called brushless “monster” mini fan, ¥19.38 paid (model FC-6638D, rated 1800mAh, 91×35×191mm, Type-C charging, folding). Features: about 10 speeds, a small LED digit display, plenty of airflow — about 50 grams of thrust on top speed, folds for carrying. Opened up: the main connections use plugs, easy to repair; lots of motor wires, confirmed brushless, the motor should be a 1503, 5-blade prop. The cells are dreadful: no capacity rating, no markings at all, negatives joined so they’re in parallel, and the unit has no BMS. Since it’s open anyway, he swaps in two high-capacity cells and adds a BMS against over-charge and over-discharge; welding with the AWithZ welder is handy, and it’s bumped straight to 5000mAh — over twice the original. Verdict: excellent value for ¥20, he suspects the seller is running a charity; a controller board alone for a home-built 1S brushless fan costs ¥20-plus online. 1368 comments: many say later batches cut corners and only have one cell, and the price went up; someone at the same shop plans to fit 2 EVE 33V cells; someone shows a fan with 800-plus grams of thrust.