The dual 18650 unit wouldn’t be used in this manner and could use any type of paired batteries. The requirement for protected button tops only stands for the single 18650 unit.

Thanks for the warning tho for sure.

Question while we are on the topic… The second bullet point… That won’t cause an explosion if they are just not perfectly matched, or will it? I thought doing that was just not great for battery life and efficiency. Aka, one worn cell and one good cell, the worn cell will dtain the good one… Sort of like the slowest buffalo scenerio? Just curious. I’d avoid doing that regardless.