Those are massive! You need a big, hot and high watt iron for that.
I am using flux core solder and it seems to work well.
Anyone tried one of these?
Wal front 50mm Lead Free Solder Pot,110V 150W Soldering Desoldering Bath Titanium Plate 200~450℃ https://www.amazon.ca/dp/B07DNYJZXM/ref=cm_sw_r_cp_api_i_UdGmFb1YT56RQ
Looks awesome for tinning the wire ends. Pop the wire end in the pot while you heat up and put solder in the connector cups, take the word out of the pot and put it in the hot connector. Seems like it might work. Just don’t spill the pot of hot solder on your lap. ?
