I'm having a heck of a time putting Deans connectors on my battery packs. I have melted 2 female sides trying. I've tried silver solder & flux and rosin core solder & flux.I've tried two soldering irons - both pencil tipped. One is 60 watts and the other has a boost to 130 watts. I cleaned and tinned the tip and both sides of the joint before soldering. Both irons worked fine for the first joint but then didn't seem to get hot enough for subsequent joints. I pulled and cleaned the tips again, being sure they were very tight when put back. I end up having to hold the iron on the joint so long that the plastic around the connector melts. I've tried holding the connector by the metal part with hemostats acting as a heat sink, but then I can't get the solder to melt adequately. Am I doing something wrong? Is it the irons? Any suggestions for a better one?