Wait so if I am using 18650s... I should use that number that can be like 4.xx (ex: 4.19) and NOT 3.7 like I have been doing?
Correct. And yes, the one Randy has will work great. I have one of his for backup. Always use the off the charger voltage. I don't know about you, but before my batts hit 3.75v I'm already swapping them out for a fresh one. You'll see what I mean as soon as you have a meter...