Producing the Bosch-compatible charging plug

Solder the middle ones first, so it will not move out of alignment.

Do not solder two pins of the same tab right after one another, you might melt the helper piece.

Hold the regulator down with something while soldering it in. This is the hardest part.

Test that the alignment is good!

You need about 18 mm stripped off of the outer jacket.

Don't forget to cut off the textile threads.

Strip only 2 mm from the jacket of the wires.

Tin the end of the wires before trying to solder them to the board.

Take a huge drop of solder on the soldering iron to create a large blob that will keep the wire strongly in place.

If you took off too little of the other jacket, you will have a hard time sliding in the board.

Pay attention to get the orientation right! The corner marking helps.

Make sure the white wire is not going to be stuck between the two pieces of the plug assembly.

Test! It need to charge with 4A, that is around 180W when the battery is near full charge, or around 145W when it is low.

Attach a warranty sticker if the power test is passed.

Second description

This uses the pre-assembled PCBs from JLCPCB.

BOM:

To assemble, we need to:

Clean the chargers. These chargers look like shit unfortunately, they need to be wiped off with a wet cloth or paper + cleaner spray. They need to look attractive!
Find the soldering helpers. These don't last together: if the holes are melted too loose, throw them and print new ones.
Cut off the original plug at the very end - let the cable be as long as possible. We throw out the original plug.
Use the stripper to take off about 15 mm of the black outer sleeve
Cut off about 1,5 mm from the black wire (this will help later!)
Strip off just 1 mm from the end of the black and red wires
Put some solder on both ends
Pull the bottom part of the 3D printed plug onto the cable
1. It should fit snugly, but it should slide. If the cable slides easily in the plug, you used the wrong plug

Put the 5 tabs into the holder, and put the PCB on it
1. It will fit easily, and will wobble around a bit
Solder one of the middle pins first
1. Use the soldering iron to keep the board level. Use super little force, very delicate
2. You want to work quickly, otherwise you will melt the holder and the whole thing is messed up
3. Also, you don't want much solder to flow down on the tab
4. But you DO want the hole to be filled, and the solder to be shiny and nicely wetting the pad
5. You will need to work pin-by-pin, 2 pins per tab
6. Do not use more solder than necessary - it will make your life harder
Do one of the outer pins next
Do all of them
Deposit a bump of solder on the two big pads: + and -
Leave the PCB stuck in the holder helper tool

Double check that you have the plug lower part already on the cable
Holding the cable from above, solder in the black wire first to -
Now carefully solder in the red wire to +
1. Now the fact that it is 1 mm longer helps you!

Use the triangle marking on the PCB to align to the triangle corner on the lower plug part (otherwise it will be upside down)
With the PCB still stuck into the holder helper tool, carefully push the PCB into the slot on the lower plug part
1. You need a little force to fit it in, and once it is mostly in, a little bit more force to push it all the way
2. Get the alignment right! Otherwise you will break the plug or need to use way too much force
The same way, put the top part of the plug on
1. It need the be nicely flush all around
Take two M3 screws, and cut off 2 mm from each
Set the drill to 1Nm! If you use more, you will ruin it
Use the drill to drive them in

Plug it in to AC! The LED should be green.
Plug it into a battery that is not full
1. It should pull around 130W
2. The battery LEDs should show it is charging
3. The LED on the charger itself should turn red
Let it charge for 10s
Check again if the charger is nice and clean!
Attach warranty sticker to side