Repairing a “50000mAh” solar powerbank

A friend of mine brought this powerbank in for repair. He had already opened it and noticed a burned wire going from the battery pack to the board, which he replaced. But it still didn’t work.

Opening up the case, revealed the battery pack sandwiched between the LED-panel and the solar panel. The USB board is kept in place by two tabs in the case. The batteries are five typical no-name 18650s. Total capacity 10,000 mAh on a good day, nowhere near the 50,000mAh on the specs.

The internals of the powerbank. Led panel on top, batteries below,solar panel on bottom (not visible) and USB board to the right
The internals of the powerbank. Led panel on top, batteries below,solar panel on bottom (not visible) and USB board to the right

Seeing the diameter of the wires used by the factory was shocking. Keep in mind this powerbank is supposed to supply 3A to the 2 USB ports (one is rated 1A and the other 2A) plus whatever current the flashlight part needs (completely forgot to measure but the IC specification says 1/3W, so around an Amp).  One of the cables connecting the USB board to the flashlight had melted through the insulation.

Cables removed from the powerbank. In order from top to bottom 1)Battery negative to USB board, 2)Battery positive to USB board (replaced by my friend), 3)USB board positive to flashlight and 4)USB board negative to flashlight
Cables removed from the powerbank. In order from top to bottom 1)Battery negative to USB board, 2)Battery positive to USB board (replaced by my friend), 3)USB board positive to flashlight and 4)USB board negative to flashlight
View of the powerbank cable connections. The melted cable between the board and flashlight is visible.

 

 

 

 

 

 

 

 

 

 

I decided to remove all wires and replace them with larger diameter ones in order for the powerbank to be safe(r). First step was to desolder all wires and clean the PCB holes, in preparation for the new wires.

The flashlight board, with wires removed and pads cleaned, ready for soldering the new wires. Notice the shoddy placement of the controller IC on its pads.
The flashlight board, with wires removed and pads cleaned, ready for soldering the new wires. Notice the shoddy placement of the controller IC on its pads.
The USB charging board ready for the new wires.
The USB charging board ready for the new wires.
Rear side view of the USB charging board. Nothing to see here, move along
Rear side view of the USB charging board. Nothing to see here, move along

I decided to use some 0.75mm² cable I had laying around to allow for the full load to be drawn safely and with lower voltage drop. At the same time I also touched up the flashlight controller IC, as a couple of the solder joints looked iffy.  The new cables although a lot larger than the original still easily fit in the PCB holes. The manufacturer could easily have used better-rated cable, had they not been trying to save every penny.

Comparison of the original cable and the cables I replaced them with.
Comparison of the original cable and the cables I replaced them with.

With the wires soldered in, it was time for a test of the individual parts. First up the flashlight. I hooked the PCB to the batteries with some alligator clips and pressed the button. And there was light and plenty of it at that.

Low (left), Middle (center) and High intensity (right)
Low (left), Middle (center) and High intensity (right)

Next I applied power to the USB board and that worked as well.

The USB board powered from the battery pack. A "Charger Doctor" was used to check the voltage output on both ports.
The USB board powered from the battery pack. A “Charger Doctor” was used to check the voltage output on both ports.

After checking all the important bits I turned my attention to the case. I noticed that the piece of transparent plastic covering and protecting the flashlight board was smaller than the case length. This in itself wouldn’t be a problem if the case cover wasn’t metal and thus conductive. I was a bit apprehensive to leave it like that, since it could short against the PCB components. The solution I came up with, since I didn’t have any spare transparent plastic, was to apply some electrical tape to the inside of the case cover to insulate it from the PCB.

The powerbank case with the translucent plastic cover for the flashlight PCB. The gap to the right was just enough to be able to short the components on the PCB.
The powerbank case with the translucent plastic cover for the flashlight PCB. The gap to the right was just enough to be able to short the components on the PCB.

After that I put everything together for a final test.

The powerbank assembled and working.
The powerbank assembled and working.

So I left the powerbank to discharge and then fully charged it up again to check everything was OK, and sent it off on it’s merry way.

 

 

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