Welcome to BLF.. Nice UF-2100 i need one of those
The charger is fine the batteries .. no those arent worth $2 dollars.
Keep in mind most budget batteries are always over state their true capacity. id suggest looking at the Trustfire flames 2400mha
and check out these threads
https://budgetlightforum.com/t/-/5826 Battery test/review
https://budgetlightforum.com/t/-/6990 What batteries should i get?
batteries go boom? Im not a battery nancy just pull the batteries out when they are finished. and never run below 3 volts thinks most say below 2.5 throw it away. I charge mine around 3.5 volts. Protected cells helps prevent high current draw, low voltage drain and over charge.
http://www.lygte-info.dk/info/battery%20protection%20UK.html explains in detail the 18650 battery.
moT