Soldering is not something that you just do. There is a technique that you learn by doing it over and over again with someone watching. If the flow is not correct, the bond is non existent. If you leave the iron on the battery to long, you will burn through the membrane that Ken was talking about. Each battery has two ends, a positive end and a negative end. That gives you two chances of damaging the battery if you do not do it correctly.

If you DO decide to solder your own packs, then go to a site like RadicalRC.COM and get batteries with the solder tabs already tacked on. This way, you solder to the tabs and not to the battery ends.

But, as a few of us have already suggested, just get the packs already made up. This way you have a good pack that has cells that have been soldered by pro's.

CGr.