Sunday, December 4, 2016

Advantages of a DIY battery for your KX2

DIY battery for KX2
At least one seller on eBay is offering a do-it-yourself 11.1V, 2600 mAH battery that will fit in a KX2. They don't mention the "KX2" part but it should fit since all others of this type do (I'll let you know soon enough!).

You may be tempted to ask "Why spend $25 for a kit battery when $15 will buy one that's ready to go?"

The answer is that you're not only getting a protected battery, you're getting the ability to buy quality 18650 cells in the future without having to replace the protective circuitry.

In other words, you could use this battery as long as the no-name cells last (which, in my case, seems to be a good amount of time), then replace them with Tenergy, Sanyo, Panasonic or some other reputable brand for about $6 each. Just be sure to buy the version of these cells that doesn't have the raised button on the positive terminal.

This kit offers the way to replace your KX2 battery for about $18 without having to buy a whole new battery. After all, it's the cells that eventually wear out, not the circuitry protecting them. This also offers the flexibility to use 18650 cells of higher capacity such as the highly-rated Orbitronics (which actually uses Panasonic cells but see note below*) for a KX2 battery with 3400 mAH capacity.

Of course, this concept applies to existing KX2 batteries from Elecraft and Tenergy as well - replace just the cells, not the whole battery.

Another source to consider for a protected $33 battery with 3500 mAH capacity:
3500 mAH batteries
Protection circuit

*A word of caution - not all 18650 cells are the same physical size. My generic pack is comprised of cells measuring 19.1 X 66.2 millimeters. This fits into a KX2. I have a variety of 18650 cells currently on order and will measure them with a caliper, check for fit in a KX2 and will post all that info here sometime around mid-January.


  1. John, Great information. I like the idea of rebuilding the pack. I would rather use my own RC charger to do the cells with the outboard balancing circuitry, which is excellent and very expensive. So your further info is very helpful!

    1. Same here, WR. With all the RC stuff I already have, I wanted a way to not have to buy something similar to what I already have. The only possible "gotcha" here is that physical tolerances of the 18650 cells have to be closely considered. Normally, as hams we only consider the electrical characteristics of things but for fitting a battery pack into a KX2 or similar rig, size considerations creep into the mix.

      Back in the day, all batteries of a particular form factor were exactly the same size. That's not the case anymore...