Ohh now that is a long life for those , nice going Steve
The only downside to this baby..is it doesn't fit in your bra quite as easily when you have no pockets!
So, for now I am not going to build a 3.7 with 2 14500 batteries. From what I have read, there is more hazard with batteries running in parallel if one of the batteries has a lot lower voltage than the other, and at this time, I am not ready to take on that liability. There is always that risk when stacking batteries, but from what I read, the risk is greater with 2 running in parallel, than 2 batteries running in series, like in my 5 volt box mod.
I will look into some larger boxes that can accept an 18650 batteries. I can likely still keep it small, but the cost to make, along with batteries is probably only a few bucks more, so is likely the better option. I would love to hear from some electronics experts on this.
Steve, couldn't you just put in a user replaceable fuse between the two batts that would protect from an overload if one cell is discharged?
I am good at soldering, but that is the only claim I am going to make. I have no idea if a fuse would solve it, but I doubt it.
I am also constrained for space with the current design. for now, I will stick to the current designs I build, and eventually will come up with an 18650 mod of some type which will acheive a much greater battery life than my current 3.7 box.