Oh right I didnt know that about 3.7v, any reason why it does that? Thanks for the info
Because they are nominally rated at 3.7 volts.
I was oversimplifying the picture somewhat, in my previous post. In reality, they discharge quickly from 4.2 to 3.9, then the rate at which they discharge decelerates to around 3.8, whereupon they discharge slowly and evenly downwards till around 3.3, and then the rate at which they discharge increases again. (This is at 10 amps - see the diagram below)
Look at how little the amp hours are, for the red line, between 4.2 and 3.8 volts, and then see how much longer it is down to 3.6 volts. That is what I meant in my earlier post.
A lot of mech users build to a sweet spot at the top end of the charge, from 4.2 to 3.7, but that is where they discharge the quickest. The advantage of this is you get the highest wattage vape, and it is easy to tell when the vape is getting weak, and you only have to recharge from 3.7 up to 4.2. The disadvantage is reduced runtime between battery changes.
Others build to put up with a little bit of a hot feisty vape to begin with on fully charged batteries, and then the build settles down and the vape is "good" down to around 3.3 or 3.2 volts. The advantage of this a longer runtime between battery changes, and a longer time with a vape that is not too weak. The disadvantage of this is the vape can be too hot to begin with, and you risk running your batteries too low if you aren't careful.
The way this works out all depends on the material you use for your coils, combined with the gauge and number of wraps. It is a balancing act, trying to get a vape at the temperature you want, at a given voltage and it all takes a lot of experimentation.
If you use steam-engine.org to plan your builds, the thing you are looking at is the "Heat Flux", which tells you how hot a build will be at a certain voltage.
