Help calculating theoretical vaping time of stacked batteries

[jmanning]

I am definitely not an electrical guru, but I think I know how to calculate theoretical vaping time for a single battery, take mAh divided by amps times 60, to get minutes.

So for 3.7v @ 1.5ohms = 9.13 watts, 2.47 amps using an AW 2900mAh 18650 battery, you would get about 70 minutes of vaping time.

But, how does this apply to stacked batteries? Do the amps get split 50/50 between the batteries?

For 6v @ 4ohms = 9 watts, 1.5 amps, using AW LiFePO4 500mAh batteries, do you take half of the amps, 750 ma, giving about 40 min, or is the full 1.5 amps being drawn from both batteries?

 

[mistinthewoods]

My understanding (and observation) is that batteries used in succession (stacked) provide a combined voltage and a common mAh. Meaning a 750 mAh lasts about as long as a stacked pair. Batteries used in parallel (like in some DIY mods I've seen) provide the voltage of a single battery but the charge life of two.
Probably not entirely accurate but that's the way I understand it.

 

[BuzzKill]

Batteries in series ( stacked ) have the capacity of ONE of the batteries I.E. 2x 800mah batts have an 800mah capacity.

Batteries in parallel have the combined capacity of both batteries

Stacking gives you 2x the voltage with the same capacity , parallel gives you 2x the capacity with the same voltage

your calculation may be close but that is a continuous ON state. We use them in a duty cycle mode or on/off this actually can increase the time to discharge by allowing the battery to cool , batteries last longer cooled vs hot.