What fuse to use? / where to get silicone cable 350°C?

[DrYak]

So i'm planning to connect Bosch tool battery (18V) to Pinecill v2. {...} I'm guessing using one that would brake if 24V or 3.8A is reached (just a guess )

Disclaimer: I work in biomed research, I might get things wrong.

According to the specifications, Pinecil v2 is a 88W soldering iron. At 18V it would pull 5A to reach that power. So I would guess: take a fuse that trips at 6A, maybe? If more than that are pulled from the battery, there's probably a short on the cable and the fuse should trip to protect.
(check also the max ratings of your battery, and set max wattage accordingly on the pinecil).

Another question is there to be bought multi-core silicone cable (2 cores) that is same quality as one that Pine64 USB cables are made of,
so temperature heat resistance up to 350°C and super smooth feeling.

You mean you want something like the original USB-C  cable, on which you want to solder/attach a barrel for your battery?
- I've found silicon smooth cable on AliExpress in the past (mines were only rated up to 200C, you'd need to search for 350C).

- Otherwise, gut a USB-C cable and solder it directly on your contraption+barrel (you'd be wasting unused data lines and the two USB-C plugs, though).

- Otherwise, adding a car/truck "cigarette lighter" port 12V-24V charger that supports USB-C PD  and plug the original USB-C cable (the cig-charger will take care of negotiating voltage and amperage. Just use one whose input support the whole 12V-24V range (e.g. also compatible with 24V trucks) and not only 12V (not car only)).
(Use a real charger, DO NOT use a passive USB-C receptacle, IT WOULD BE DANGEROUSLY NON STANDARD. Normal USB devices expects to start at 5V, and negotiate higher voltage using USB PD or QC protocols. They shouldn't get straight 18V. If you plug a device that doesn't withstand 18V (e.g. a smartphone) you will certainly damage it).



NOTE: above links are the articles I've bought in the past, there might be cheaper/better offers by now (e.g.: my car charger is 30W only, there might be 65W or 100W by now?)