[Elecraft] 3.7 V Li-Ion cells in the KX1

[James Kearman]

I thought someone had done this already but can only find AE5X's 
suggestion that it could be done.

http://www.ae5x.com/kx1.html (near the bottom)

I bought six 14500 Lithium-Ion cells rated at 3.7-V each from 
batteryspace.com and successfully installed them in my KX1. The battery 
holders are originally wired in series; they must be wired in parallel 
for this mod. I had problems making the cells touch the contacts in the 
holders, so I had to put a blob of solder on each positive contact. This 
requires some care to avoid melting the plastic. With the cells in place 
I get more than 3 W out on all bands, 80-20 M.

Charging the batteries requires some care as they can do nasty things if 
overheated. Because I'm going to travel in Europe starting next week, a 
homemade supply was out. I needed something that would pass muster at 
the airport. I bought a charger designed for three cells in series, and 
good for 1 A. It's a 12.6-V switching supply with unfiltered dc output. 
The advantage for me is two-fold. It looks commercial, so the inspectors 
shouldn't be alarmed at the sight of it; and it also operates on 100-240 
Vac, so I can use it in Europe. BTW, the charger comes with the 
clip-lead accessory. You can download a datasheet for these cells at 
batteryspace.com, study it, and surely build a safe charging supply. 
Maximum charging current is 750 mA; limit voltage to 4.2 V per cell.

Jim, KR1S