Using the data collected by OH8STN on the Yaesu FT-891 radio power consumption, a battery pack can be picked out to provide power to the HAM radio on expeditions such as SOTA or POTA.

The pick is a battery at about 100 greenbacks, that should cover double the maximal usage of Yaesu FT-891 at , which is a complete overkill and will thus provide a very long runtime in order to be able to make a large amount of contacts. Technically speaking, emitting at is more or less good if you're transmitting from within a cave but for normal usage, it is possible to wrap around the globe with a maximal emitter output of (assuming a transmission occurring in non-environmentally crippled bands at the time of writing, namely the bands between 15 and 30) due to the wonders of the Single-Side-Band (SSB).

Of course, the battery pack can be used for any apparel that accepts as input current, such that the teardown and minor adjustments should be feasible for any other application.

All that considered, the chosen battery makes a perfect companion and branches away from the typically "blue batteries" with an additional case and convenient voltmeter. Taking a peek inside would be a good idea, to make sure that everything is in order, given that such creations commonly are delivered with just bad circuitry that needs a little patchup, as well as to potentially attach terminals for the wires required to power the equipment.

The interior of the case contains a bunch of batteries that are connected together in order to yield , with a bunch of wires connected to a battery BMS attached on top of the batteries, and with connectors leading to the outside of the box, one of the connectors providing power, the other meant to be used with a charger.

As a bonus, the battery pack is also delivered with a charger, boasting which seems dubious given its size and build.

One minor adjustment that is made is to add screws for terminals, which seems to be a simple enough catch-all solution, that can be used both for HAM radio operations as well as providing bench power for other projects. The only requirement would be that the leads are crimped with o-ring car connectors that fortunately enough are cheap, in ample supply at any car shop and fairly tough.

For an elegant connection, butterfly screws are used that make it easy for an operator to detach hardware from the battery pack if need be.

Initially, the wire from the terminals was connected to the BMS directly, bypassing the button that the power pack has available, which was deemed later to be undesirable and ended up in a rework to make the battery only apply power to the terminals in case the battery pack is switched on.

With a bit of a hassle, the terminals are rewired, with the ground going to the BMS and the hot wire being attached to the power-on button such that power will be provided to the terminals only when the battery is switched on.