As cyclops2 said, it is definately correct. To properly solder the cells it requires a good quality iron that can deliver a high temp on contact. As he said, it only takes a second to make the joint. You don't want to apply a lot of constant heat on the cell ends or it will cause damage. If you have access to cells with solder tabs already, it is a bit easier but you still can't apply high constant heat when soldering them either. The right tool for the right job.