The battery pack died on my bike light and I was left in the dark, so I decided to go the cheap route. I went to Batteries Plus and bought 4 AA size Lithium batteries. Each cell was 3.6 volts. I strung them together in series parallel to make a 7.2 volt battery pack. Then I grabbed the charger from my light set and chared the batteries for a couple of hours. The next morning, I hooked up the makeshift light set and went for a road ride. Everyghing seemed to work fine.
Yesterday evening, I put the batteries on the charger in anticipation of a morning ride. Set the whole thing on the garage floorand went into the house to read. About an hour later, I heard a very loud gunshot out in front of the house. I ran to the window, but didn't see anybody. I went outside and opened the garage door. The garage was filled with smoke. The battery pack was in pieces.
Sometimes creativity is rewarding, sometimes, not so much.