I bought a lot of stuff for playing with lithium ion batteries.
An ATORCH DL24 150W electronic load.
https://nl.aliexpress.com/item/1005005210461952.html Have to verify its accuracy. Definitely not good for the internal resistance as it seems to report it to high.
A cheap battery spot welder.
https://nl.aliexpress.com/item/1005006437044413.html Works pretty well. On max (5) it burns through 0.1mm nickel strip, but on 3 it makes a nice weld.
A Liitokala Lii-500 battery charger.
https://nl.aliexpress.com/item/1005005343417996.html Got this one because it has internal resistance measuring, but it looks like it is not very good at it. Reading is to low. For charging and discharging it works fine.
A Liitokala Lii-M4S battery charger.
https://nl.aliexpress.com/item/1005006437015680.html Got this one because it has a storage function, where it charges or discharges a battery to 80% capacity. The test function of this one is better than the Lii-500 test function. It reports both the discharge and the new charge capacity. Have to verify its accuracy too.
A YR1035+ internal resistance meter.
https://nl.aliexpress.com/item/1005006706324000.html Got this one for a more reliable internal resistance measurement. A friend of mine recommended it and I also found it mentioned on several forums as being a nice instrument. Have to do some tests with it.
A very nice 4 wire holder for batteries to do measurements.
https://nl.aliexpress.com/item/4001322976384.html This one can be used with the YR1035+. Actually got two of these but replaced the cable with thicker wires for the current flow, to be used with the ATORCH DL24 electronic load. It is nice and sturdy and makes testing a battery easy.
Aliexpress made me customer of the month.