Using an internal resistance tester for crimps and connections

[offgrid-curious]

I'm building a DIY battery and bought an internal resistance tester on Ali Express to validate the resistance values on my cells. Aside from the battery, I'm assembling a bunch of the components for my install ahead of time, since my install location is nearly 2 hours away. While testing internal resistance of the cells, it occurred to me that I could also use the tester to check the resistance of my cables and connections.

For example I measured 0.67 mohm between my switch input and the positive bus bar.



That makes it easy to calculate the voltage drop across the switch depending on the current, e.g. 0.067V at 100A (and it will dissipate 6.7w). Another neat measurement is that there is approximately 0.02-0.03 mohm of resistance between posts on the bar.

I'm thinking that I can do this between all of the connection points of the system to verify that all of my crimps and connections are good before turning things on and performing an actual load test.

Does this make sense?

 

[hwy17]

My BMS IR reading has so far reliably indicated when a bus bar was not tightened enough, which seems kind of like a confirmation of your proposal.

I don't know how my BMS is able to measure IR when the testers seem so much more complicated. But I think it has something to do with the fact that the BMS doesn't have to supply the current load, it just reads the external current load on the battery and the compares it's simple resistance readings with that dynamic.