Just to add a bit more context:
I did some battery research at U-Michigan back in the day for DARPA (not my project, was helping a colleague), and I also did a lot of testing of batteries for ICES PEMF products. I could easily buy a house for the amount I spent on this testing, which involved:
Continuous testing for about 5 years
Testing all relevant battery chemistries at the time (NiMH, Li-Po, Li-Ion, Alkaline)
Testing all relevant battery sizes and configurations,
Testing discharge voltage and series impedance (ability to deliver power)
Continuously for each discharge cycle
Under a range of loading conditions to simulate all possible system loads for ICES-PEMF devices
So, I tested well over a thousand batteries, each for many recharge cycles (when rechargeable)
It was a massive task, at great personal cost and effort, that took half a decade.
So, I feel I can say, with sincere humility but firm confidence that I know a bit about batteries.
The first thing I can tell you is that you can’t say much about a battery by taking a single voltage measurement on a few batteries. Batteries are too variable in their manufacture, they change with use, abuse, loading conditions, recharge cycles, and other factors.
So, I graphed all of this out, wrestled with the data for a year or so, and developed several designs, which I tested extensively to optimize their use of batteries. I selected a small number of battery forms that would achieve the primary design objectives: biologically active ICES-PEMF that was ultra-portable.
Most of the behavior of the selected battery types is baked into my system designs for the M1 and A9. That is, a big part of the hardware and firmware design is specifically to optimize for battery performance. And it works; I tested it, I measured it, and I can prove it. ICES-PEMF devices will run at least twice as long on the batteries for which they were designed than any other similarly designed knock-off PEMF system. For almost all of the PEMF systems that pirate my technology, they change the circuit a bit to save a few pennies, but then they lose this aspect of the design. So, their pirated system will:
(1) drain the battery about twice as fast, or
(2) run longer if they do not bother to actually energize the coils (a sham system)
The newest 9V Li-Po batteries, the ones that are USB chargeable and claim to be “real 9V” have internal voltage boost which generates a less clean voltage than a simple battery, but in that case the voltage output is limited to fixed values by the battery chemistry, for example, about 8.4 volts for Li-Polymer.
The ICES-PEMF battery management strategy will handle this type of battery well, and it will also minimize the amount of “dirty” voltage you get from this type of battery in two ways.
First, the internal voltage regulation and charge storage will smooth those ripples out so that they do not get sent to the ICES-PEMF coils.
Second, the bursts of “dirty” voltage from those batteries are minimized by the way that energy is drawn from those batteries.
So, you can rest assured that I put a great deal of thought into battery management, optimization, and use for ICES-PEMF systems. My advice is that you will get the best overall performance if you follow my simple recommendations for charging and swapping batteries. The complex stuff is all baked into the internal hardware and firmware.