I have a ciggreen 7 box mod and just noticed today that only one of the batteries is firing. Any ideas? The site where the battery is the one that is firing.
You comment is confusing, "site where the battery is the one that is firing" makes no sense.
Looking at the mod I like what I see, a rather elegant approach.
The top battery (pos) is a solid plate and the switch contact is solidly mounted to it. Seems that part should be fine as you say it fires. I would check the bottom NEG contacts, if you own a multimeter see if there is continuity, touching both should give you a beep (if your meter has that function). Multimeters make this kind of troubleshooting a breeze and they don't need to be expensive, this one has a beep for continuity and auto shut off. For a vaper and with light use it should be fine.
Meter XL-830L
The 2 bottom contacts should basically be functioning like one solid bar.
That said this is such a simple design, Make sure your POS contact points (the nubbins on the top plate) are in fact making contact with your battery and are clean, that same with the bottom bent tabs.