Go portable with an external battery pack

FT-817 external battery pack
FT-817 external battery pack

The FT-817 is a feature packed and capable radio. Its rugged construction is small enough to fit nicely into most modest backpacks making it the perfect travel companion and ideal for 'in field' DXing.

But there are limitations. The built-in batteries will not last thirty minutes when transmitting, that's not really practical. Also, the internal battery supply will limit you to 2.5 watts of power.

An external battery pack overcomes these problems.

This page explains how to make an effective and lightweight LiPo battery pack and power lead that will keep your FT-817 powered all day.

This project is not limited to the Yaesu FT-817, I am sure the battery pack lead could easily be adapted to suit other similar radios like the KX3, KX2 or other portable rigs.

What you will need

The following items can all be purchased from the regular web-based sale sites:

  • 11.1V 5500mAh 3S 20C Lipo Battery Pack
  • T-Plug Connectors Male and Female + Heat shrink Tubing
  • AC Compact Balance Charger B3 Pro for 3S Lipo Battery
  • 1.7mm x 4.0mm Male DC Power Plug Connector Jack
  • In-line Standard Blade Fuse Holder for 12V 
  • 5 amp blade fuse
  • Twin flat red and black wire

You will also need:

Soldering iron, heat gun, solder and, cutters

Making the lead

Solder the parts together, ensure all joints are well made. Here are some tips:

  • Tin the wire so that the solder runs under the insulation (makes the join more robust)
  • If the joint is not right the start again
  • Buy and use the proper heat shrink
  • The fuse needs to be as close to the  battery T-connector as possible

Note: Basic soldering skills are required, ask if you need help.

Charging the battery and switching on

FT-817 external battery pack lead
FT-817 external battery pack lead

With a trickle charger, the battery will reach full capacity overnight. Just plug it in and switch on, the charging process will start. 


!!!Do not leave batteries unattended when charging. They do occasionally explode!!!

!!!Do not short out the battery, it can explode!!!

!!!Protect the battery from damage like excessive bending or piercing!!!


Once charged, plug the lead into the back of your FT-817 and connect the battery. You will be able to enjoy many hours of full power, low interference operation from one charge.

Making it a little better

Add a ferrite to your new battery lead and make a short PSU lead with a female T connector. Now your new power lead is multi-functional, it can be used for both PSU and battery operation.

FT-817 external battery pack kit
FT-817 external battery pack kit

How does it perform?

It performs great! This simple but effective project makes the Yaesu FT-817 truly mobile. The battery pack is lightweight and will power the FT-817 for most of the day on 5 watts of power.

I use mine with the Sotabeam antenna to make mobile DXing a piece of cake. It all fits in my day bag along with my other hiking items. 5 watts USB from a high and interference-free location is often much better than a suburban high-power base station. Don't take my word for it, try it for yourself.

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