Li-ion pack assembly, AWithZ spot welder

Helping a friend strip a pile of power-tool batteries from the scrapyard into cells (18650 1500mAh 5C) for a high-capacity 12V pack: remove the BMS (tin the iron, lift with both hands), peel the strip (shorts and sparks very easily — sparks twice on camera), grind the weld spots off with an angle grinder, IR-test every cell; the newly arrived AWithZ H2 handheld welding pen tacks the ends first then welds everything, 0.12 strip is easy; 3S BMS with B+ and four wires, output 11.77V; insulation must be done properly or it sparks; ran out of heat-shrink so no shrink wrap

A friend picked up a lot of power-tool batteries at the scrapyard and wants them made into 12V. Remove the BMS from each battery: undo two screws, a little solder on the iron tip, lift with both hands and it comes off; do the same on all of them (cells marked 18650 1500mAh/5C); peel the nickel strip off one by one — careful not to short, this step shorts and sparks extremely easily, one slip and it looks like this (sparks on screen); wipe every cell clean, grind the weld spots off with an angle grinder so they weld well; IR-test each cell’s voltage and IR with the IR meter; pre-cut the strip plus the two main + / − strips. The AWithZ H2 handheld welding pen arrived today, give it a try — long-press the bottom to power on; tack the two ends of the pack first, then weld the whole thing, the welds look very good, 0.12 strip is easy. B+ on the BMS to the positive, held with insulating tape, four wires soldered on; BMS output measures 11.77V, OK; solder the output leads; everyone, do the insulation properly or it will spark; the blue heat-shrink ran out so no shrink wrap. Comments: ‘professional or not, shorted twice’; what use are old batteries; mine is 48V.

Outcome

Steps5 steps · click a frame to jump

1. 
   1. Remove the BMS: two screws, tin the iron, lift with both hands

   Scrapyard tool batteries into 12V; remove each battery’s BMS: undo two screws, a little solder on the iron tip, lift with both hands and it comes off.

   00:01 – 00:30
2. 
   2. Peel the strip: shorts and sparks very easily (sparks on camera)

   Remove all the BMSs the same way (cells 18650 1500mAh/5C); peel the strip off one by one, don’t short it, this shorts and sparks extremely easily, one slip and it looks like this.

   00:30 – 00:56
3. 
   3. Wipe clean, grind the weld spots; IR-test every cell; cut strip

   Wipe every cell clean; grind the weld spots off with an angle grinder so it welds well; IR meter on each cell for voltage and IR; pre-cut the strip plus the main + / − strips.

   00:56 – 01:23
4. 
   4. AWithZ H2 spot welding: tack the ends, then weld all, 0.12 is easy

   The AWithZ H2 handheld welding pen just arrived, long-press the bottom to power on; tack the ends first then weld the pack; welds look very good; 0.12 strip is easy.

   01:23 – 02:05
5. 
   5. BMS B+ to positive, four wires; 11.77V; insulate against sparks

   BMS B+ to the positive, held with insulating tape, four wires soldered; output measures 11.77V OK; solder the output leads; insulate properly or it sparks; heat-shrink ran out, no shrink wrap.

   01:52 – 02:26

Bill of materials

Measured on camera

Creator’s tips

• Removing a BMS: solder on the iron tip, lift with both hands; watch for shorts when peeling strip 00:14
• Grind old weld spots flat with an angle grinder before welding 00:56
• Test voltage and IR on every salvaged cell and group them 01:09
• Tack the ends first to locate, then weld the whole pack 01:38

Pitfalls

• Peeling strip shorted and sparked (twice in the video, criticised in the comments) 00:44
• Ran out of heat-shrink, no shrink wrap 02:19

Li-ion safety

• Peeling strip shorts and sparks very easily; the BMS area must be insulated properly or it sparks 00:44

Quotes