I ran into a similar issues recently -- I've owned my KBOX mini + subtank (kit) for a few months now. I recently picked up a new tank (Bellus RDTA) and was using it successfully on the KBOX mini up until last night. I got maybe a couple days usage with this tank without issue (and I was able to get the KBOX to fire 0.3ohm coil which I believe the docs say is the lowest it'll fire) until I rebuilt my tank to 0.25 ohm and it wouldn't fire (of course) -- oddly enough, it WAS firing the 0.25ohm coil for over a day without issue. Now the battery light blinks 10-12 times when trying to fire it.
I put my original black subtank mini back on, works fine. Couple of things I noticed:
1 - no spring loaded 510 pin. Really? I read something on reddit about retro-fitting a spring-loaded 510 pin into the KBOX but I'm not going to try, it's out of my league.
2 - The insulating rubber grommet around the 510 pin is a bad design idea. Taking tank(s) on and off the KBOX will eventually wear this part out. I saw a cool post on Reddit (again) where a guy screwed on a 22mm finned heatsink and then screws his tanks into that. This method should keep this grommet intact and the heatsink has an adjustable center 510 center pin.
Just interesting (to me) that the original KBOX (the silver one with LEDs on it) seems to be better designed/built than one of Kanger's flagship devices.
I've been a Kanger person since I started vaping a year ago but I have to say, guys, you need to step up your game to compete out there:
1 - Any of your mods SHOULD have a spring-loaded center 510 pin and SHOULD be better isolated from the frame than a simple rubber grommet that wears out with usage. Since it's a "non replaceable" part, this looks to be designed obsolescence. Considering I paid almost $100 for the kit, I'd expect better quality.
2 - Take cues from companies like UD and their Bellus tank. I was able to fire this tank on my KBOX mini @ 50watts and it was absolutely awesome. I can't fire any subtank I own (original+kit, v1+v2 rba) at anything over 25-30watts because it can't wick fast enough. The best thing about this other than the vape was the form factor, easily portable whereas my RX200 is a lot beefier and not exactly a mobile vape mod (imo)
Sorry Kanger, I think you're getting a touch out of scope here. The current Kanger devices seem to be built for fashion rather than function. I find myself leaning more towards competing companies because their designs and builds seem to be the way Kangertech USED to be.