GLV mini uses one 16340 for 3.7v
GLV can use a 16340 and a spacer, or an 17670(maybe) for 3.7v.
For 6v it can use 2x 3v 16340s (rcr123a) stacked.
For 5V it has a fixed resistor built into the device to drop the voltage off the 6v stack.
If you go with the 5V model you are pretty much stuck at 5V. Unless you purchase a different head/switch assembly to swap out. Additional head caps are $45
Madvapes has a few inexpensive box mods.
Custom Mods
They are not great, but if you are one a budget and don't want to build your own its a solid device for a very reasonable price. They ship from North Carolina and shipping is usually quick any where on the east coast.
Janty stick is not a bad choice. It seems to perform as expected for a battery of its size and capacity. I personally see no need in a mod with a smaller capacity than an ego. Couple that with the price tag and I've grown to despise this mod, but other people love it and speak highly of it.
Did you say you got your ego from Tasty Vapor? I'm not sure if Geoff is honoring warranties on parts anymore. Hopefully he'll help you out though. Geoff's a good guy. Those weren't egos then btw. They are knock offs. Riva's I believe. The knock offs have had more failures than real Joye Egos.