Hello,
I own this mod for around a month. I bought it and also bought two different 26650 batteries, an Ijoy INR26650 4200mah and a Basen 26650 4500mah. I first used it with the Ijoy battery which is shorter and it worked fine. When I inserted the Basen battery, which is a little bit longer, and screwed the battery cap the mod inmediately got extremely hot (shorted) but I was able to unscrew the battery cap before any damage happened. It could have been destroyed the first day I received it. Later that day I understood what happened, when using the Basen 26650, the battery cap can't be screwed completely because it causes the short circuit. I have been using it mostly with the Ijoy battery, but I have used it with the Basen, I just stop screwing the battery cap when it gets tighter and always pay attention to any heat when screwing the cap.
I have been using the mod after that almost every day and it works fine. I still would not recommend anyone to buy it because there is an obvious fire risk.
This is my first and probably my last Hcigar product if they don't fix this problem for us.