Hi. I'm happy to add more words, but a photo of my setup would be impossible to understand (including dozens of irrelevant wires doing other things). My THREE heater pads run around 2.4A each (varying according to supply voltage). With just one of those heater pads, the pad "-" could connect directly to the JK multi-wire heater interface cord, with "+" permanently connected to the "12v" bus (or optionally connected through a switch as well).
In my own "12v" case the current through all 3 pads is too much for the JK interface (about 70W maximum at high voltage, it's also limited to 3.0 Amps as an absolute maximum current value). Only the the coil "-" is connected to the JK interface. (This is the automotive coil, "Bosch" type also sometimes listed as 'JL9214', I left the 5th pin unconnected.) The RELAY COIL draws only a tiny bit of current through the JK interface when JK-BMS enables that ground connection internally. "Coil +" is connected the 12v supply, in my case through a separate enabling switch (a very small one).
On the Relay switched power circuit connections, one side gets +12v from the main power bus (in my own case, with multiple batteries attached). the other side goes through a 4-way connector to reach the 3 "+" power terminals on the heater pads. (A wiring nut is adequate, although I nvere use those for so many wires within my vibrating travel trailer.)
From a later message in the Thread, you will see that the BMS passed the "single heater pad" test with no issues at all (A+). Following subsequent instllation into my travel trailer, the JK-BMS has also controlled the Relay circuit (and all 3 heater pads) PERFECTLY in a chiller induced test. That resulted in about 100 watts of total power through the heater pads.