Soldering the Wire (Attempt 1 - Failed)

What happens here

The creator attempts to solder the stripped red wire back to the battery terminal using a large soldering gun and the included solder. However, the solder does not adhere properly. It's noted that the solder might be old or lack sufficient flux, hindering the creation of a clean connection. The large size of the soldering gun also makes precise work difficult.

Goal: Re-attach the broken wire to the battery terminal