Hi Mark,
As you know, the Sanyo 20700B is 4000mAh. Mooch reported them as 16A 4000mAh.
However, two of them in a Series Stack (like the Captain) will give only very slightly more than 4000mAh, with the same Amperage rating (for the Stack) as one of them in the Stack, but twice the Voltage.
Two of them in a Parallel Pack would get you that 8000mAh, with twice the Amps of one in the Pack available, but only 4.2 Volts.
Is that VC4 also a battery analyzer that will show you what mAh you are really getting? Wish I had a LiitoKala Engineer Lii-500 or an Opus 3100 v2.2 for that!
And Hey, where did you find Sanyo NCR20700B in stock? Wish I could find the Sanyo NCR20700A in stock!!!
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I went through battery junction for the 20700b.
I'm pretty sure the vc4 does have an honest analyzer function, though I never got around to reading about it; I mainly use it to check battery voltages at the start of charge. I've had great luck with Xtar, the only make I've used since 2011.
I understand series and parallel batteries. Net, as long as one doesn't stress the amps (pull too many amps), available runtime is still linearly related to mAh for a given output power (available watt hours divided by (output power times conversion efficiency times cutout factor)).
In a series-buck I would have 2x3.7v, with 4000 mAh, while in a parallel-boost the gozinta is 3.7v with 2x4000 mAh. In both cases the available notional energy is 2 x 3.7v x 4000mAh = 29.6 Wh.
We may not get to use all that energy, due to cutout (the mod will generate a cutoff if total voltage from the battery(ies) is too low, show a weak battery kind of display, we don't really get to drive the batteries down to the point of no energy remaining) and conversion efficiency (energy lost in the boost or buck conversion). The particulars of a given battery, plus a given mod's design, will determine what the cutout factor is.
Boost vs buck is somewhat of a shrug, either implementation will be tuned to have a maximum operating efficiency in a certain range of output (real components vs. ideal).
I'm looking forward to getting the Captain in - two pairs of fresh 20700b as well as several 18650 pairs available [emoji5]