Been using dewalt 18volts for almost 20 years, with no problem. I like the newer dewalt charger that will charge all three batteries, Li- ion, Ni-Mh, and Ni-cd. When battery come up to full charge, the charger shuts down and battery cools off.
I did take a Li-ion battery apart because it went bad. Discovered it had a computer processor built in. I could tell the smoke had left the processor.