A bit off, is an understatement. Most all comercial reasonably priced Battery Chargers/ analyzers measure battery internal resistance (IR) using a dc voltage drop method. Calculate the IR by measuring Vdrop against a known load. Unfortunately to measure such a low resistance you really need to incorporate a 4 wire kelvin method of measuring the IR accurately of a cell. The opus manual even states that the readings can vary 10% to 20% and that you need to subtract 30mΩ from the reading due to contact resistance. There is absolutely no correlation between actual IR of a cell and what the Opus gives you other than that it is wrong. Get yourself a proper IR meter RC3563 or a YR1035+ and you will have a proper IR reading you can trust the first time. No need to check it two or three times and hope you get a reasonable reading that is wrong anyway.
Aren't the spring ends insulated? So it doesn't touch the battery? The tracks seem to be on the front where the negative terminal is attached, so if anything wiring against the negative connection and the track endpoint would be the way to go, but it is a pain to mess around with, and have to use some super flexible wire to cope with the strain.
It may be sad but it is true in my case as well. But then again why would you use the OPUS for an IR meter in its own admission just contact resistance will add ≈30mΩ to the results. As far as any off the shelf Battery Analyzer/Tester that claims it does IR is just hoodwinking you.
