My DIY projects out there for the curious souls to see.

      I needed some MOSFETs for a four channel constant current load but didn't have any besides some counterfeit IRL3803 MOSFETs I had received from aliexpress. I mean these are still MOSFETs inside, just very small ones. For my load I need something that can handle 1A and max ~5W dissipation, so let's take a look at the silicon die and see whether these will work or not. The method described is only good for a rough estimate, but at least allows you to make use of the MOSFETs instead of tossing them away.     First I need to crack one open, which I already did when filing a refund, so that's done. I also need a genuine MOSFET as reference, that we'll use to extrapolate the approximate characteristics of the counterfeit MOSFET. For this I chose a blown NTD70N03R.  I used this website to take the measurements: https://eleif.net/photo_measure.html     The area on the fake IRL3803 die is abut 1.45sqmm and the area on the NTD70N03R is about 6.6sqmm, ...

      I got a defective Airwheels pack from my internship and it had 64 18650 cells inside, of which 16 were dead but the remainig 48 were still good. And I saw this as a great opportunity to make a big lithium battery pack for other projects, like my homemade electric scooter, for example.     These packs are most often welded together with spot welders but I don't have one. Previously I used to solder to salvaged batteries. When I salvage batteries I leave a piece of the nickel strip on them so that I can solder to it later. But for a big pack soldering would take ages, not to mention how tedious it would be trying to get a good solder joint without cooking the cell. Oh and don't forget the mountain of solder it would take and all the fumes you would be huffing the entire time. Because of this I decided that it's finally time to build myself a battery tab spot welder.     I've previously explored the world of spot welders many years ago and even expe...