The most detailed tutorial on the net: spend ¥100-odd on a flashlight that lights up a whole building, and along the way learn a universal car / e-bike / motorbike spotlight and a universal drill battery pack. Spotlight: a ¥19 18W car spotlight from Taobao, converted to 100W; the LED board is made by a friend (upgraded version about ¥70, link on request), about 70 LEDs; materials: retaining ring, 4 screws, step drill bit, thermal grease, 63% solder wire 0.8mm, quick connector (not needed for the flashlight, for bare car-light installs). Remove the 4 faceplate screws and the centre screw to take out the reflector (don’t touch the inside of the reflector, it leaves fingerprints), 2 board screws, cut the positive and negative wires; bore out the original glue hole with the step drill for a thicker power cable; the original 18W board can become a desk lamp. Coat the back of the housing / board with thermal grease (the thinner the better), wipe the LEDs with a cotton swab and alcohol; drop in the retaining ring to hold the reflector; the original 50-LED reflector must be bored to M10 for 70 LEDs, control the force; solder the power leads to + and −, if the pads won’t take solder scrape them a few times with a blade and add flux; feed the wire ends through the hole into the housing before soldering to the board, joints should be rounded; fix the cable hole with Kafuter 704 silicone sealant for waterproofing; fit the reflector, the seal ring, tighten the centre screw, the clear lens, screws; power-on test OK, apply waterproof sealant; the spotlight has thermal protection. Handle ¥7 from Pinduoduo, 21700 battery case (Dayi-style, drill-compatible) about ¥11 from Taobao; 21700 cells about ¥3 each, 4000mAh, 40A discharge; the welder is an AWithZ. Twist the spotlight’s blue (−) and red (+) wires together and reinforce with solder; wiring fast-forwarded (the phone overheated and the step of placing the power cells into the retaining ring was missed: place them one by one following + and − on the circuit board, DM if unsure, see the April 12 drill battery tutorial); after welding the pack, fit the charge/discharge BMS with two diagonal screws, solder the joints with a soldering iron, rounded joints; put the pack into the bottom shell, button spring, solder + and − to the charge indicator, fit the charge indicator plate as trim, top cover screws, stick on the ‘Upgraded — lasting power’ decal; power-on test, switch works; outdoor test ‘the whole building lit up’, shot on a stock Samsung camera with no exposure adjustment; this is the flood version, swap the reflector for a spot beam; parts list by DM. Comments: the all-in-one board throttles after 30 seconds / a minute or two (an 18W housing converted to 100W can’t shed the heat, 17/14 likes); at nearly 200W the battery lasts an hour at most; no driver? creator: all-in-one temperature-controlled board; missing a cooling fan; a four-leaf CNC housing costs ¥300.