That is a timed capacity test, to see how much you can draw out
Aka how many ampHrs the battery has
A load test uses a much higher amp draw for 15 seconds and the voltage has to stay in the green on the load tester
In your case perhaps 100 amps
Your coffee maker will draw any where from 700w aka 60 amps single cup brewer, to 1500w 130 amps for a full size kurige
Our under cabinet drip maker is 900+ watts
Are you trying to brew coffee from full charge or after the capacity test
Trying to brew coffee from at or below the 50 percent SOC
Seems like a bad idea to me
Why not charge to full, do a normal night of tv etc..
And then check voltage and brew coffee in the morning
Check all cables especially chassis ground, remove clean re-tighten
You could try a non calibrated load test, by brewing coffee with fully charged batteries