What Soldering Iron do you use?

I use 2 - 80watt Weller and a 100/140 Weller gun. 90% of what I need to do can be done with the gun. But for batts and bullet conns 5mm and up, 80watt iron gets the nodd. Much faster and just does the better job.

Check the nuts that hold the tip (if they are still made this way - my gun is ~40yr old) - they will loosen over time getting hot/cold and heat transfter goes way down if they are even a little loose.

For batteries, you don't want heat conducted into the cell to possibly damage and weaken the batt. A gun takes too long to melt solder on the end of the batt and the batt bar mainly cause tip is small and heat is conducted away too quickly. What used to take me 5 or 6sec with a gun to do on a batt, now takes just about 1sec with the 80watt iron. I would have to redo some of the gun joints too cause I could pop the bar off. That doesn't happen with the iron.

Hakko is available lots of places outside RC world. You can find it without the decaling if you want.