I am not trying to scare people, just to make them aware. What could happen.
I also do not advocate against any particular company for now.
I used to sell over 14 different types of li-ion chargers, with various results.
Basic rules (from my experience)
If you can have both - it is the best option- but either one would significantly decrease your risk of using fire extinguisher
1. Li-ion battery must be top of the line battery. (do your research - there are many battery tests/reviews available)
2. Charger must be designed with safe charging in mind. (fewer reviews, but still good starting point for using best charger)
3.Go to batteryuniversity.com, to help you understand even more.
You follow these basics, and you will be on the safe side.
Do your research on batteries / chargers (forums about batteries and flashlights are good place to start - there are some highly respected forums discussing batteries and chargers in depth ) .
Be safe