This post describes how the newish Power Delivery (PD) mode mobile powerbanks can be used to power a SOTA transceiver as well as keeping your other hiking devices charged.
The PD protocol enables fast charging of mobile devices from a powerbank by negotiating a high voltage for the mobile device if fast charging is supported. Common fast charge voltages are 9 and 12 Volts. When the device to be charged is connected, serial data messaging transacts between the powerbank and the mobile device to establish a supported fast charge mode.
The 12 Volt capability of the powerbank got my interest as it would be a simple way of supplying power to a SOTA radio. The powerbank that I have can deliver 12 Volts at 1.5 Amp. This is more than enough for a 5 Watt CW rig. When powering the KX2 transceiver, I had to limit the power output to 5 Watts on SSB.
Typical powered devices that are in the backpack for hiking include a USB chargeable head torch, a mobile phone, USB chargeable Garmin and a USB chargeable 2 metre portable. All these devices can be charged by the one powerbank.
This PD power bank was purchased at Big W for $27 on special. It claims to have a capacity of 10 Amp Hours. Of course, the stated capacity is at the 3.6 Volt cell voltage. I ran a discharge test at 9 Volts (PD mode) while repeatedly charging a Galaxy phone. When the measured capacity was scaled back to the 3.6V battery voltage, and assuming an efficiency of 85% for the voltage converter, the battery capacity worked out at 9.4 Amp Hours. I didn’t really expect it to be this close.
In order to trick the powerbank to think that it has a fast charge device connected, you need to connect a PD trigger device between the powerbank and the load. The trigger device in the photo was sourced from Ebay. It communicates with the powerbank to trigger a 9 V or 12 V output. The trigger device also can display voltage and current.
I did not notice any significant RF noise from the powerbank or the trigger unit on 40 and 20 metres.
The PD Trigger unit probably would not stand up to life in the backpack without some more protection and connector strain reliefing. This particular unit has a model number of XY-WPDT and is available from a number of sources such as Ebay or Bangood. This unit also comes with a cable and connector that fits the QCX Mini and KX2 although it looks like the centre pin might not be quite the correct size.
There are smaller PD Trigger units that are integrated into the cable connectors that might be more suitable for the backpack.