I needed to replace some NiCD batteries for a drill I have. The new Battery pack was $100 and I could buy the individual cells for <$20, so I decided to replace them myself. The only ways to connect the cells was to spot weld or solder them with heavy duty wire. I needed a hi power (wattage) solder iron and they cost as much as the new battery pack. Found this slightly lower wattage soldering iron for a good price and it works great! Now whenever one of my battery packs go out on my many cordless devices I can replace the cell myself. The biggest benefit is you can find higher capacity cells than what the OEM battery pack usually provides, so your devices will run longer between charges.