I'm having problems now locating the two youtube videos I remember seeing. (have they been taken down?) Although I appreciate the video flyblue posted and how it does point out good safety features, the problems I saw demonstrated in the other videos were
not addressed. These both seemed to indicate a problem with the upper charge control board, not with a
battery (spark or bank) short. I've seen several small switching supplies fail over the years, with some getting hot enough to melt plastic, but none ever caught fire. One popped its fuse.... does your product have any fuses? Smart electronics are spiffy but in the end a dumb fuse is a very foolproof feature against catastrophic failure. Most (but not all) of my car chargers (for various devices) incorporate a fuse right in the cigarette lighter jack. Unfortunately, very few of my home units do. One had a high voltage diode in the mid-stage rectifier short out and that resulted in a burnt off trace and smoke emitted due to not having a fuse. Neither smart electronics that shut off power delivery to the peripheral nor thermal sensors could have prevented that from smoking the trace.
I would like to review the videos again, specifically the one showing the melted spot on the top and compare it to what electronics are positioned directly below that spot on the charge control board that's below that spot in the charger. When I looked, it wasn't clear whether the heat had come from above from the
battery in slot 2 or from below inside the power bank, I would like a closer look. It does look like your case is fire-retardant which is good. I'm most interested in seeing the buck-down regulation circuit which I believe is on that upper control board, as that's usually where all of the
battery bank failures I've seen have occurred, usually caused by a failure/overheat of the bucking IC or shorting of one of the associated schottky diodes.
Edit: I was looking in the wrong place for the info of course, this was
Amazon reviews. So I found the video and reviewed it as well as the pictures. The one with smoke is hard to tell what's going on, but it looks slightly more likely to be the top board that is smoking, not the
battery pack. (which, all things considered, is the
preferred place for overheat/fire!) The other review with pictures only is more informative, showing the top case being melted in two places. The center spot is above your current sensing resistors for the middle bay, which you describe as flameproof. While the resistors may be flameproof, they can heat up the case enough to melt it, which is what looks like happened here. The melt to the right is a bit harder to identify the source on, but I believe it's the buck IC for the right bay that's a bit more to the right than the melt suggests. This is probably due to the contoured shape of the top case at this location, making the area immediately above the IC a little thicker than that to the left, where heat will rise anyway, leading to the melt appearing a little bit to the left of the chip.
It would be interesting to see what the state of the electronics in these units is. Something shorted out, and it's not necessarily the
battery. What did you find when the customer returned the units?
