A follower recommended a so-called brushless turbo mini fan, ¥19.38 paid (model FC-6638D, rated 1800mAh, 91×35×191mm, Type-C charging, folding). Features: about 10 speeds, a small 7-segment display, plenty of airflow, about 50 g of thrust at the top speed, folds for easy carrying. Inside: the main connections use plugs, easy to service; lots of motor wires, confirmed brushless, the motor should be a 1503, 5-blade prop. The cells are pretty poor: no capacity rating, no markings at all, negatives joined so they are in parallel, and the unit has no BMS. Since it is open anyway, swap in two high-capacity cells and add a BMS against over-charge and over-discharge, welded on the AWithZ welder, quite handy, straight up to 5000mAh, twice the original. Verdict: great value for ¥20, suspect the seller is running a charity — a controller board alone for a home-made 1S brushless fan costs ¥20-odd online. 1368 comments: many report later batches cut corners with only one cell, and a price rise; someone from the same shop plans to fit 2 EVE 33V cells; someone shows a fan with 800-odd grams of thrust.