Repair the Philips SCE-7640 powerbank
For my work, I'm using a a Philips SCE-7650 powerbank as a battery pack for my equipment. Allthough this powerbank is quitte old, it still does the job. Why I'm using this powerbank? Well, it's quitte compact, has a 4 led power indicator, and a 19V output which you can also use to powerup your laptop (or other things that need more that 5V).
Inside the SCE-7650
Internally the SCE-7640 uses 4 Li-cells (2000mAh/each) in series, followed by a PCB which contains a Li-cell charging circuit and some DC/DC converters for the output voltages.
Internally this powerbank uses Li-cells, but, after several years, or bad storage, these batteries run out. In order to repair the powerbank, you need to replace the batteries, but the original type of Li-cell can be hard to get or quitte expensive. I found out that the case of the powerbank has enough room to fit a standard Li cell 18650. These type of cells are easy to get and are cheap. 4 of these cells costed me around €10,-.
Build replacement battery pack
- Tape the 4 cells together using kapton tape, since the space within the case is quitte limited, use 2 layers max. Add some hot glue between the cells and under the kapton tape in order to fix the cells more securely.
- Solder the cells in series together, don't weld too long since it can damage the cell.
- Use silicon wire, (AWG22 will do), since this is flexible, it makes it a lot easier to wrap it all together.
- Remove a small white plastic stand from the case, use pliers for this, or else it won't fit. The stand is under the PCB.
- Fix the battery pack inside the case using double sided tape.
- When soldering the wires to the PCB, start with the Gnd, then +3,7V, and so on.
- Place the temperature sensor somewhere under the kapton tape.
- Before powering it up, measure the voltages on the PCB from the battery wires.
- When everything looks ok, connect it to the charger, the LEDs should start blinking.