What it is?

It is a simple converter allowing to use popular 18650 batteries tester (like Opus BT-C3100) to test other lithium batteries like Lithium polymer ones. This is more neat way of testing cells with wires instead of terminals and avoids danger of disconnection during testing.

Parts

You will need:

-9cm of any nickel plate, i used 8mm wide and 0.2mm thick
-terminal block, probably this *elevator* type one will be better then the one I used
-soldering iron recommended

Assembly

Total length of one nickel plate: 7+12+32+4mm = 55mm, since you need two such pieces: 110mm = 11cm. You may use these dimensions to prebend nickel plate before and make your life easier.
Insert nickel plate to the top hole which has end. Then bend it over the terminal and mark where it should be again bended to get back inside the part. After that, take it all nickel plate out, bend in marked place, cut the longer leg so that it will reach the terminal block and mount it for the last time. To connect a plate with terminal block I used soldering, just prebend the terminal legs and plate to touch each other firmly, add solder to the tip of the iron and jam tip inside hoping that you will make a connection - may be tricky and you may melt some plastic but no big deal... I am looking at all of you perfectionists :)

Updates

13/04/2021
initial release

Sources

-Terminal block:
here

-HDR Aerodynamics Workshop environment:
here

Found 10 3D-models for “btc3100” across many websites

Opus BT-C3100 - 80mm Fan Mod

OPUS BT-C3100 charging voltage regulator

OPUS_BT-C3100_voltage_regulator_v2

Opus BT-C3100 80mm Fan Mod (for Small 3D Printers)

Opus BT-C3100 - 80mm Fan Mod Vertical

18650 universal batteries converter for testing Lithium Polimer Li-Po and others

Opus BT-C3100 Battery Charger Wall mount

Opus BT-C3100 - 80x80mm 25mm fan

Opus BT-C3100 - 80x80mm 25mm fan

Opus BT-C3100 5015 blower mod