Ultralight Hike
While hiking on the Habichtswaldsteig I thought about what an ideal power bank for me should look like. I came to the conclusion that the perfect power bank for me must have the following features:
Ideally, the BL-51YF batteries of my LG G4 smartphone should be usable in the power bank. Since I found the smartphone battery variant so appealing, only the DIY solution remained for me.
In the course of my research I was brought back down to earth, as I could not find a charging circuit that met all my criteria. The charging circuit that came closest to my requirements has an input current of 1.5 A (1.7 A in pass-through). So unfortunately I had to compromise here. Next I ordered the following Onite charger for LG G4 batteries in order to have a proper charging cradle for the batteries. This charging cradle unfortunately lacks contact points for the temperature sensors built into the batteries. This would be essential for charging at 2 A. Since the charging circuit only charges at 1.5 A, this point can be overlooked.
After the components had arrived, I soldered the charging cradle to the charging circuit and tested it at the ULTF autumn meetup with a 3000 mAh battery of the LG G4. This battery was charged to 90% within a misty autumn day with the Kolumb 10W solar panel solar panel.
After the general functionality was verified, I removed the previous electronics from the charger and made room for the power bank charging circuit using a Dremel and a scalpel.
In doing so, I experienced how narrow the line between “it is still too small” and “damn, much too big” really is. Therefore, the holes for the display and the power switch are a little larger than expected.
In the next step, I glued the circuit board in the case with UHU Endfest 300 epoxy adhesive and nearly glued the power-on button stuck in the process.
After carefully cleaning the button of the dried epoxy adhesive, another functional test followed. Both charging and discharging continued to work. The button was also movable again.
Here are a few specifications of the MYOG power bank
| Charging current when charging battery | 1.5 A |
| Current during simultaneous charging and discharging | 1.72 A |
| Current when discharging | 1.6 A |
| Weight without battery | 55 g |
| Weight with 3000 mAh battery | 102 g |
| Weight with 9600 mAh battery | 205 g |
All in all a nice project that was a lot of fun and now has to prove itself on the next tours!
