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Hi! ... Maybe I can help add to the confusion ... lol
The 3.7 = 3.7 volts = 3.7vdc = 3.7 volts direct current; yep, that's battery voltage. That is the
power of your battery. Your car has a 12v battery; the headlights use 12v - but, when you plug your cell phone in the cig lighter to recharge it - the adapter only uses about 5v of that.
The supplied stock KR808 battery is, I think, a 280 = 280mAh = 280 milli Ampere hours. This is the
capacity of your battery. It's kinda like the gas tank in your car - your 280 runs longer than my 150 (Joye 510), but not as long as somebody's 500.
Your KR808 battery has a "Protective" circuit in it that allows it to only absorb a max of 4.2v - no matter how long you charge it. It also prevents it from discharging to less than about 3.2v - no matter how hard you puff on it.
So . . . you notice it's
"All Good" when you have a freshly charged battery (4.2v) . Sadly, on these little batteries, it's immediately "all downhill" from there until your battery shuts down! Worse, for me, is that the
"Good Times" with my 150mAh don't last as long as your "Good Times" with your 280mAh.
What to do? Throw money at it! Buy the 380mAh KR battery! Build or buy a "mod" (modification) that gives you 500 to 300mAh!
Welcome to the club & Good Luck !!!