Metal Type C Input DIY 5V 2A USB Output Kit Box for Case 4X 18650 Battery Charger for Mobile Cellphone Tablet DIY

Parts do not fit together properly on both battery boxes, and when sliding the case over the batteries, it is so tight and the edges are so sharp, that the battery insulation was scraped off. Please note that you get what you pay for! Very inexpensive battery boxes that went directly into trash bin after several minutes of attempting to assemble. Two batteries that were damaged during assembly attempts also landed in the trash bin.

Given the price and the existing singular lousy review, I did not go into this with very high expectations. But I have to say, I am blown away by this cheap little gadget. It's a pretty niche use case but it's exactly what I wanted.If, like me, you are nerd with a pile random 18650 cells lying around looming over you and threatening to avalanche at any moment, this is perfect. Because in the above case, it's really rather silly to have to buy and pay for a power bank just for it to have someone else's crappy cells in it when you've got oodles of milliamp-hours sloshing around unused anyway. Why can't you just buy an empty box with no cells in it, and just slot in your own? Well, with this you can. And you can control the quality and capacity of the cells going into it or, more likely for us types, just jam whatever salvaged spares you've found into it which brings your total assembly cost very near to zero.I did learn a few things about this and putting it together which I'll outline here. First, yes, the cells are a tight fit in the casing. This is what you want so they don't rattle around in there. My example arrived with the aluminum case bowed in just ever so slightly, probably from being squashed during shipping, but it was easy enough to bend it back out. After that it went together with no trouble, except for this detail to watch out for:There is a wire running from the circuit board to the negative terminal block which is easy to get in the way of either the 3rd or 4th cell, which if you trap it underneath either of those cells will cause it to sit proud of the cell holder just enough that the assembly won't go together. You want to ensure that this winds up fully BETWEEN these two cells, not underneath either of them. I used a small sliver of thin kapton tape to ensure that wire stayed put. That's because there are two little prongs molded into the plastic to attempt to hold it in place for this purpose... but they didn't actually manage to grab the wire at all.The included board handles both charging and discharging, but offers no provision for balance charging so you'll want to find four cells with roughly matching terminal voltages to get the best results. There is a USB-C port for charging and a full size USB-A port for discharging. You CANNOT discharge from the USB-C port and vise versa, which I guess is a bummer. But what do you expect for the price? The USB-A port will output "2 amps," or rather 1.8-something in reality, which should be good enough for most purposes. No form of USB-PD or Quick Charge output is provided whatsoever but again -- look at the price. You also get four obnoxiously bright white LED charge level indicator dots on the end, which can't be adjusted or disabled but thankfully the board goes to sleep pretty quickly, within about 5 seconds, when it's not producing any output anymore.The charge/discharge controller board and cell holder arrive preassembled. No actual electronics experience and certainly no soldering is required; just jam your four chosen cells into the battery holder and get them the right way around, and then slide that entire assembly into the aluminum shell. A bezel is provided which clicks pretty firmly into the power-button-and-port end of the assembly. There are no screws. You will need a spudger or similar tool if you never need to take it apart again in the future. I recommend testing and ensuring everything is working before you click the bezel on, because it's a hassle to get it back off.The endcap is printed with a huge "10400 mAh" marking which I find pretty rich, because the actual capacity of the device will of course depend entirely on what cells you've stuffed into it. How would they know? This figure assumes you'll put 2600 mAh cells into it, which I certainly didn't. I used some 3000's I had lying around.