There exist USB chargers that can be considered industrial in the sense that they are made to work for a very large number of devices. For example, the pictured USB charger that was purchased for this project can power up to 20 USB ports in order to charge deices.

The seller is cautious when expressing themselves, claiming that that the charger can output and such that each port would have maximum available to a device.

Visually inspecting the power supply, it does not look like it would offer given its size, with chargers that can supply typically being much larger. In engineering, sometimes savings are made by estimating the actual "realistic" load that this charger would be under. In this case, it seems like only half of the current advertised, or is supplied and more than likely the producer estimated that there will not be 20 devices plugged-in at the same time and that realistically the charger will be used with 10 or less devices.

Once open, the disassembly indicates a pretty tidy yet straightforward build with a top charging plate consisting in an array of USB Type-A sockets and a standard power supply underneath that provides power to the USB charging plate.

Even so, there are some interesting things to mention here. The charging plate for the USB array actually has two distinct power-lines that divide the whole PCB in half, with one of the power lines supplying 10 ports and the other power line supplying the other 10 ports. However, the two lines are shorted together such that the power supply powers both at the same time. The idea behind the split-power PCB is that each set of 10 ports would receive power from a different power source in order to minimize the current requirements, the size of the power supply and to be able to mitigate a short by separating the two lanes from each other.

Another interesting thing looking at the charging PCB are the connections that are made between the USB ports and the PCB. Using some solder wick and a solder gun, the two middle-pins corresponding to the D- and D+ ports are cleaned and the result is thrown under the microscope.

As can be observed, the D- and D+ ports are shorted together. Shorting D- and D+ is a trick to make any USB device that connects to the charger believe that the charger is a Direct Charging Protocol (DCP) device. When an USB device, such as a phone, a drone or a hair trimmer is plugged in, the devices typical emit some signals to determine what type of charger they have connected to and how much current can be drawn.

Shoring D- and D+ is the functional equivalent of switching the device into DCP mode charging and in DCP mode the charger may supply up to . However, the USB charger is advertised to be able to supply and that means a maximum of per port whereas, in DCP mode, every port should be able to pull from the charger which the charger cannot provide.

With those details established, this USB charger does not conform to its own design so for that purpose this USB charger will be redesigned by us such that it can reach its maximum potential.

An old power supply from a Juniper Networks VPN unit was salvaged and then cleaned up. The power supply is rated at on the line, which means that it will be able to supply the per USB port correctly.

The power supply is however larger such that a larger enclosure was purchased. The box that was purchased was a large junction box measuring made out of plastic that matched the power supply innards perfectly and with some little space to spare.

The junction box was then cut to match the front USB array plate.

It fits well and some ideas come to mind such as adding some terminals in order to turn the project into an all-in-one power supply - something that might be approached at a later date.

Both the junction box and the faceplate are now scratched or sanded such that they can be painted over in order to achieve a better look than just black.

Now, the power supply itself is not that modular, in so far that it is made to fit the aluminum enclosure but the connecting wires and other contacts are permanent and soldered such that the power supply must be fit with various connectors to ensure that the result of this project can be easily disassembled.

Here is a list:

• the USB array will be connected with a 4-pin square molex from a motherboard,
• both original fans from the power supply are removed and they are replaced by a single larger fan; similarly, the connector is removed from the heat-sensing PCB and a JST connector is used instead,
• the original kettle socket is removed and the socket is replaced with a more powerful filter

The usual paint routine is applied to the junction box, namely, primer, followed by paint, followed by laquier and, in this case, followed by flame retardant paint within the junction box itself.

Fitting the components is a breeze. Note that the junction box contained some struts meant to screw-in PCB, just like the power supply but they were not enough and they were not correctly placed such that they were sawed off and then new struts were added by gluing PCB standoffs to the base of the junction box.

The box is closed and turned on to observe the results. Without too much messing around, the small LEDs on the USB faceplate come on and the project comes to life.

This device is really worth it and even with our modification project that expands the enclosure of the charger, looking side-by-side with a regular 1-port USB charger, the project saves a whole load of space.

Placing 20 chargers for each USB port next to the box would end up with a volume three times the size of the box or more so making the project a little larger whilst minding the actual USB charging standards was well worth it.