Hi there. Batteries can be very confusing at the beginning. Unfortunately, many vape store employees are not a good source of information. They really ought to know more about what they're selling.
Anyway, you've received good advice about the protected batteries you have. The sort of batteries that are used for vaping used to use a more dangerous chemistry, so they required protection. Then they switched to a safer chemistry. They aren't entirely safe, but the batteries we use now are less dangerous than the old protected ones were.
The other thing you need to know about 18650s is that they're not like AAs, which are more-or-less interchangeable. Some models of battery can provide more power than others. If you get a low-power 18650, it might not work at all in a vape, or it could even vent or explode when you try to use it. The most important battery specification is the CDR (continuous discharge rating). Unfortunately, some stores and many rewrapers and off-brand manufacturers lie about batteries' CDR. Those Nitecore's aren't 35A, and while VTC6s can be good batteries for vaping, they certainly aren't 30A.
There are two ways to get a fairly accurate CDR:
- Stick to reliable manufacturers (Sony/Murata, Sanyo/Panasonic, LG and Molicel) and get the CDR from the manufacturer, not the shop. Since batteries from these manufacturers are often counterfeited, it's also important to stick to a reliable shop.
- Check Mooch's tests, which @Letitia linked to above. Mooch is our resident battery expert. He conducts testing to determine the actual CDR of various cells.
Next step: Here's how you use the CDR. The top wattage you ever use in your mod should be less than:
3 x Number of batteries in your mod x CDR
Since you're using a dual battery mod, a 15A battery like the VTC6 would give you:
3 x 2 batteries x 15 amps = 90 watts
A good resource for picking a battery (and a reliable shop to buy it from) is
Mooch's Recommended Batteries chart. Note the blue row, which lists some good suppliers.
Good luck!
