Ep. 35 | How handy is carrying 220V mains power outdoors? A homemade multi-function portable power station that can cook rice and run a hot pot on its own battery

54 × 18650 cells in 3S18P for a 12.6V 36Ah outdoor power box: 220V inverter + wireless charging + USB + solar charging + thermostat-controlled fans

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.

Outcome

Steps13 steps · click a frame to jump

1. 
   1. Finished build and what it can do

   54 × 18650 cells in one extra-long pack; put a phone on it and it charges wirelessly, Type-C/USB, 1200W 220V household power, can charge straight from solar.

   00:00 – 00:28
2. 
   2. Test IR and voltage, swap out bad cells

   Even new cells need testing; this 5C-discharge batch is about 16mΩ, and the few that read 20mΩ are all swapped for matching 16mΩ cells.

   00:28 – 00:55
3. 
   3. Load snap-together triple holders, fish paper on the positive ends

   Snap-together holders are flexible but not as rigid as a one-piece holder; a ring of fish paper on each positive end stops the wrap rubbing through and shorting; cap with the top holder to get 3S18P, 12.6V, 36000mAh.

   00:55 – 01:23
4. 
   4. High-power welder, double-layer nickel strip

   Discharge current is high, so the strip is doubled up; this machine has plenty of punch, two more layers would be no problem; the creator prefers auto trigger, and the machine also supports foot-pedal trigger.

   01:23 – 01:50
5. 
   5. Accident: pens touched, blew through a cell, replaced it

   The two pens touched and blew through the double strip and one cell; cut the strip, pull that cell’s holder segment out, fit a new cell and put it back, re-cut a short piece of strip — much gentler on the pack than tearing off all the strip.

   01:50 – 02:18
6. 
   6. Fit the 120A balancing BMS, bring out the main + and −

   Wrap the outside in fish paper; 120A balancing BMS; main − comes off the balance board’s output, main + bypasses the balance board; wrap the joints in copper wire, iron on max and flood with solder, then tape; connect the balance leads, fish paper on both sides, fibre tape around both ends.

   02:18 – 03:26
7. 
   7. Cut the box for meter / socket / switch / USB / wireless / fans

   BMS fixed on the pack; lay out the bidirectional smart meter, 220V outlet, power switch, USB+Type-C, charge input (step drill bit), cooling fan holes; fit the USB charge module, wireless charge module, meter, switch and 220V socket.

   03:26 – 04:19
8. 
   8. Wire the meter’s shunt

   Main − gets a ring terminal (no crimper, so solder it) and goes to the shunt’s input; a spare positive lead goes to the shunt’s positive input; ribbon cable to the meter; shunt output goes back to the main − lead, then fix the shunt down.

   04:19 – 04:46
9. 
   9. Connect the 600W / 1200W-peak pure sine inverter

   Main + lead plus a small spare positive lead go into the inverter’s positive terminal and get clamped; four thin spare leads from the main − terminal go to the inverter’s negative; fix the inverter, wire the 220V outlet and control switch, power up, runs fine.

   04:46 – 05:18
10. 
    10. Fit the 5–30V buck-boost charge module, set 12.6V

    Input port wired to + and −; the CC/CV auto buck-boost module takes 5–30V input; diode in series on the positive output; one of the four spare lead sets becomes the charge lead; clip the multimeter on the diode’s output side and set the module output to 12.6 or 12.8V; connect the negative and charging starts, working current about 5A.

    05:18 – 06:08
11. 
    11. Two fans + three 40℃ thermostat switches in parallel

    One intake and one exhaust fan; three thermostat switches stuck on the inverter heatsink, the balancing BMS and the buck-boost module heatsink, all wired in parallel — any one above 40℃ starts the fans, they stop only when all three are below 40℃.

    06:08 – 06:58
12. 
    12. Wire the wireless charger and 90W USB, screws and handle

    Third spare lead set to the wireless charge module, fourth to the 90W USB charge module; screw it all up and fit the carry handle.

    06:58 – 07:25
13. 
    13. Use-case demo

    Hot pot while fishing, plug tools straight in for outdoor repairs, jump-charge a dead e-bike; charge straight from any 5–30V charger or solar panel.

    07:25 – 07:55

Bill of materials

Measured on camera

Creator’s tips

• Test IR and voltage even on new cells; reject the high-IR ones and keep the batch matched 00:42
• Snap-together holders let you pull just the blown cell and swap it, without tearing off all the strip 01:54
• Use double-layer nickel strip for high discharge current; wrap the main + / − joints in copper wire and flood with solder 01:36
• Main + bypasses the balance board; main − comes off the balance board’s output 02:38
• Three thermostat switches in parallel: any hot spot starts the fans, they stop only when all have cooled 06:44
• Set the buck-boost module output to 12.6/12.8V with a multimeter before connecting the battery 05:48

Pitfalls

• Let the two pens touch and they blow through the double strip and the cell (‘joy turns to grief’) 01:45
• Snap-together holders are not as rigid as one-piece holders 01:02
• Without a matching ring terminal, heavy-gauge joints are hard to deal with 02:26

Li-ion safety

• Fish paper on the positive ends so the wrap can’t rub through and short; both sides of the pack too 01:07
• Wrap joints in insulating tape, fibre tape around both ends for strength 02:54
• Diode in series on the buck-boost charge output 05:32

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