In my case it was a used older cell that overheated & began to gas fumes due to the battery tube being hot from the LED that are attached to it inside. It may not happen to all 18650 cells, but its still a potential risk with a weak, older, cheaper, or damaged cell in the lantern. When it comes to lanterns in particular, i focus on all safety concerns and potential hazards. No doubt that most who have this lantern may never have a problem, but the risk is there because of the flaw in that design using the same battery tube metal as the LEDs direct heatsink. My personal feelings on this lantern is that Zanflare either reduce the maximum mode amp load, or re-design the LEDs to be on a separate sleeve with an air-gap from them to the battery tube.
About 400pcs sold for the past 2 months, thank God, I have yet to heard any serious injury or complaint so far. I recalled that one or two member did express their concerns when tailcap felt hot (40°C+ range) during usage.
3xAAA adaptors are much bigger than 18650. In lights that can use 3xAAA either the 18650 rattles around inside or a plastic sleeve adaptor is used around the 18650. So unless a device is designed with 3xAAA in mind, it will not fit in place of an 18650
In your situation, have you considered running it without a battery? I think you would need a 90° micro USB cable. Even then it may not sit flat. If hung from the handle, any usb cord would work.
Running it direct from USB with no battery limits the max output, but should be more than bright enough for a “night light”. There is no excess heat and no battery to cause a problem. Plus it will run forever.
If they made the base out of aluminum it should fix the overheating issue, maybe add a few mild fins to the base as well. Although this would increase the cost.
That’s pretty much the case it seems. It can heat a battery to around 50°C to 55°C. Most cells have an operating range of up to 60°C or 70°C depending on the cell.