#Rural Abiao

54 × 18650, 3S18P, 12.6V 36Ah. The inverter does 600W continuous, 1200W peak. The moment I plugged in the rice cooker my heart was racing — rock solid! Welded with the P60F, double-layer nickel strip in one pass, not a single cold weld. It took two evenings; the hardest part wasn't the welding, it was cramming this pile of modules into the storage box and still leaving room for airflow. The video shows the whole process. If you want to build one, follow along, and ask questions in the comments.

The creator wanted an adjustable supply that works without mains — for the price of one you can hand-build four. The core is an adjustable buck module with a coulomb-counter display; power comes from 12 × 18650 in 3S4P (12.6V) with a 3S 40A BMS. A plastic box is cut for the quick charge port, a square hole for the coulomb-counter display, round holes on both sides, vent holes and a fan slot, a battery gauge and a master switch. The charge input feeds a CC/CV buck-boost module with charge management, output set to 12.7–12.8V; two 40℃ normally-open thermostat switches in parallel control the fan (one stuck on the boost module heatsink), with the fan and gauge negatives on the boost module input. Battery 12.6V goes through the master switch into the boost module set to 36V max, then into the digitally controlled regulator module with thyristor; output leads with clips on the output terminals, the coulomb counter’s ribbon cable into the core board. Power on — charging works, the coulomb counter lights red, a multimeter on the output clips shows the knob sets voltage precisely, up to 33V; it can charge while in use, set voltage and current precisely for load tests, and work as a universal charger for all kinds of batteries.

One end of a two-metre galvanized pipe is cut at an angle and a steel plate is welded on tilted about 45° (like a small hoe); a handle is welded on wherever it feels right. Four holes in the plate take two bearings (as close to one straight line as possible), a shaft goes in and the excess is cut off, then an adapter, clamp plate and small pulley are fitted. A bracket for the 775 motor is welded on; once cool, the 775 motor and belt go on, and a powered test shows it runs smoothly. For power, 18650 cells make a 3S5P pack with a balancing BMS, fitted into a box with input / output / gauge / switch holes cut in it; the charge input gets a CV/CC buck-boost module with charge management set to about 12.8V; the battery positive runs through the switch into a boost module set to 33V feeding the 24V 775 motor — more torque and more speed. The box is fixed to the tail of the pole, the output lead connected, a shoulder strap tied on and trimmer line fitted (soft wire for now). A test cut at the front door works well — lighter and quieter than a petrol trimmer.

Two full-range (bass/treble) car speakers go into two 6.5-inch pre-cut speaker boxes: the positive and negative leads pass through the wiring hole, and the speakers are screwed in. The amp is an XY-T30L module with Bluetooth and bass/treble control; plug in the left and right channels, the speaker terminals are screwless, and it runs on 12 or 24V. To keep things simple for the older folks, he builds a dedicated power supply: 15 × 18650 cells with fish paper on the positive ends in a dedicated holder, 3S5P for 12V, fish paper around the outside against knocks, then spot-welded. A balancing BMS is a must; the multimeter reads 10.8V at input/output (not fully charged, normal), 3.6V for one group and 7.2V for two. The common-port input/output leads are connected and protected with fish paper + fibre tape. The box is drilled for a switch, battery gauge, charge input and power output; charging uses a 5–30V-input constant-voltage/constant-current buck-boost module set to about 12.6/12.7V, insulated with heat-shrink. Battery output and charge input both go to the switch input; all negative leads are twisted together, tinned and heat-shrunk. On power-up the gauge shows 2 bars; the lid goes on with screws, the phone connects over Bluetooth and plays, and the creator claims ¥1000-class sound quality. Commenters think the box size doesn’t match and a digital amp is just loud.

The heart of it is a power-bank boost module with a digital charge readout and fast-charge protocol support (about ¥10), paired with 8 × 18650 (¥2–3 each). Test the cells’ internal resistance, stick fish paper on the positive ends, load them into a single-row holder and wire everything in parallel (the module is a boost type, so it only needs 3.7–4.2V); 8 × 2000mAh = 16000mAh. Wrap in fish paper, spot-weld, insulate the positive and negative ends again with fish paper, measure 3.6–3.7V, solder leads onto the positive and negative pads and wrap the joints with filament tape. Two wires go to the module; press the switch and it shows the charge level. The case is hand-cut from PVC sheet (a 3D printer would look nicer), openings cut with a home-made fret saw and a small electric saw, glued with strong adhesive, with cut-outs for the display, the USB / Type-C ports and a small button. The Type-C port does input and output; with a powerful enough charger it goes into fast charge (green lightning icon), the USB port also fast-charges, and it will keep a phone going for two or three days.

An old powered speaker picked up at the scrapyard (under ¥1); fuse good, a hum on power-up, transformer output normal. The plan was to feed the Bluetooth module’s audio output into the original board’s audio input, but it didn’t amplify; switched to driving the speaker straight from the Bluetooth board, which works. So everything original except the driver comes out and it becomes rechargeable — 6 × 18650 spot-welded into a pack with a 3S60A balancing BMS, fish paper insulation and fibre tape; a diode and a CC/CV buck module on the charge side; a fast-charge port, charge-level display module and switch in the case; wired up, powers on, back in the case, phone pairs and plays, ‘sound quality is decent for its size’. The top comment points out that without audio amplification the result is only so-so.

The creator takes 54 × 5C-discharge 18650 cells (about 16mΩ internal resistance; IR and voltage tested first, any 20mΩ cells swapped out) and loads them into snap-together triple holders for a 3S18P pack, 12.6V full and 36000mAh; fish paper on the positive ends against shorts. Spot-welded with double-layer nickel strip on the high-power AWithZ welder; midway the two pens touched and blew through the strip and one cell, so that cell was pulled and replaced. A 120A balancing BMS goes on, the main + and − are brought out with copper wire wrapped around and flooded with solder from the iron, then wrapped in fish paper and fibre tape. The box gets a bidirectional smart meter (with shunt), a 220V socket, power switch, 90W USB fast-charge module, wireless charging module, a CC/CV buck-boost charging module with 5–30V input (output set to 12.6/12.8V, about 5A, diode in series), a 600W / 1200W-peak pure sine wave inverter, two fans + three 40℃ thermostat switches in parallel (one each on the inverter heatsink, the BMS and the buck-boost module), and finally a carry handle. It can cook rice and run a hot pot, drive power tools, jump-charge an e-bike, and charge straight from any 5–30V charger or solar panel.