I received my new Vapecell S4 plus charger today and have been testing some of my 18650 battery collection.
I have noticed most of my batteries range from 20milliohm-40milliohms but a few have much higher resistance such as 245milliohms.
What does high resistance tell me about a battery?
It tells me that your cells are very worn out or more likely that you have high contact resistance caused by the poorly designed slider mechanism used on most chargers, that give wildly inaccurate IR readings.
Take 10 readings, resetting the slider each time and take the lowest number as your approximate IR number.
I would typically agree with that statement except that the readings are consistent from battery to battery.
My “red” batteries from a laptop pack all read high milliohms where as my new Molicel P26A’s all read low resistance, same with my Samsung 25r’s.
250mΩ from used laptop cells is normal, it’s pretty rare to get anything under 50mΩ.
Look here for common values for new cells, using a standardised method : Measuring impedance - #9 by docware
The method used will change a lot the results, and as xxo mentionned, those round cell charger are not very precise.
I may not be asking my question correctly. How does a high resistance cell behave compared to a low resistance cell? 
It’s like you have resitance in series with the cell, so if you draw 1A on a 250mΩ cell you will get a 250mV drop (roughly as the internal resistance varies with the state of charge, temperature and current).
You’ll waste more power in the cell, and with the voltage drop you wont be able to draw much current.
High power cells have a very low internal resistance.
Reduces Voltage under load, limits the current the cell can deliver, causes the cell to heat up more during charging and discharging. Generally makes the cell unsuitable for high current applications. Could also be a sign of an internal short in extreme cases that may cause self discharge.
Think of current as water through a pipe. As the diameter of the pipe gets smaller. the resistance goes up, thus, less current flow with high(er) demand.
Most of the higher amp cells will test lower in resistance (Sony VTC 5A test very low)— you can get a baseline avg for cell types/brands—as they get worn out that number will rise—— the sanyo red (laptop pulls ) usually test real high over a 100
Those cells testing really high —check them on the tail end of charging —if they take forever to finish charging or get very hot when charging above 4.10 v
Toss them —they aren’t worth keeping —- their capacity is probably low also