The Ek’s Files

I really like my Elecraft K1 QRP rig. Mine’s the 4-band model (40, 30, 20, and 15 meters). I also have the KAT1 internal ATU and the K1BKLTKIT backlit display installed. It’s a great rig for QRP CW in the shack or in the pack. Mine is a staple of my Field Day excursions.

Typically, when I hit the trail with my K1, I pack a 2-AH gel cell to power it. Works great, but the gel cell is kinda heavy and bulky. So, in a moment of boredom (I had the itch to build something, I guess), I ordered the KBT1 internal battery option and installed it.

K1 with internal battery option installed

Although the documentation for the KBT1 mentions using alkalines or rechargeable NiMH batteries, my intent was always to install Energizer lithium AA batteries. These batteries are not cheap. You’ll find a four-pack at Target for about ten bucks, and the KBT1 takes eight of them. But here are the good parts:

• They have a 15-year shelf life.
• They pack a 3000 mA-H punch (even at a 1000 mA discharge rate).
• They have a very flat voltage profile while discharging, meaning they don’t drop appreciably in voltage until the end of their life, unlike alkaline and NiMH batteries.
• They’re lighter than alkaline and NiMH batteries.

You can see for yourself–here’s the datasheet. But I digress.

The KBT1 comes with an aluminum bracket, battery holder, a switch and protective diode, wiring, replacement speaker, and a new top cover that removes quickly when batteries need to be replaced. Since the normal configuration of the K1 is to have the speaker attached to the top cover, replacing the cover necessitated replacing the speaker as well (with one that’s slightly smaller and held in place by the aluminum bracket). I’ve seen a few complaints on the web about the lack of volume from the replacement speaker, but I haven’t really noticed any big difference (the audio is much better with the cover on than off).

I spent about two hours installing the KBT1. Installation is straightforward, once you remember exactly which screws to remove in order to take off the top and bottom covers. I probably haven’t opened up my K1 in over five years, so it took a minute to get it apart. As usual with Elecraft, the quality of the instructions is excellent, and the kit is made well. The only nit I’d pick is that the replacement cover needed to be tweaked a little because the surfaces weren’t quite flat and the bend was a little more than 90 degrees. These were easy things to fix.

The replacement cover is very easy to remove and reinstall–simply unscrew two thumbscrews in the back and slide it off. Another nice feature is a separate switch, recessed in the top cover, for disabling the internal batteries (to keep them from draining if the rig is accidentally switched on, and for when you want to connect an external battery).

K1 with KBT1 top cover

Once I had the KBT1 installed, I powered up the rig and noted that the battery voltage was 14.7 V. With about 3000 mA-H of capacity, this is an ample replacement for the gel cell I was using.

With lithium AA batteries installed, my K1 (including the 4-band module and the internal ATU) weighs exactly two pounds. The KBT1 option added about 9 ounces to its weight. However, I can now leave my  25-ounce 2-AH gel cell at home, so I save a pound with this new configuration.

Of course, it’s not exactly in the same size/weight category as KD1JV’s ATS-3, but I can live with that. I probably wouldn’t take the K1 out on a backpacking trip unless we’re going out for a ham radio field event anyway. For other times, I have an ATS-2 (a forerunner of the ATS-3). But I’ll bet I could run an entire Field Day weekend with just the internal batteries.