Yes, be very careful with lithium ion batteries. I recommend a store-bought charger with UL or CSA certification. Don't burn your house down (equivalent to "you'll shoot your eye out").absf, GopherT, my thanks to you both! Your selflessness and patience (in addition to attention to detail) is rarely found outside of close friends or family.
I can now move on to my next task.... Adding a lithium ion battery, charging circuit, and QI wireless charger. Any experience with those?