“Batteries for the Elecraft KX3 and Other Low-Power Radios,” authored by Belmont amateur Eliot Mayer, W1MJ, is featured in the March, 2020 issue of QST. The article talks about battery types, supply current vs. supply voltage, and battery and charger suppliers.
Mayer is an electrical engineer with a BSEE from U. Mass. Amherst and an MSE in management from the Gordon Institute of Tufts University. He works on the design and manufacturing of medical imaging equipment at Analogic in Peabody. His ham radio activities include QRP holiday-style DXpeditions, operating a K3 radio from his condo home station, guest operating at the high-power stations of fellow Yankee Clipper Club members, and 2-meter FM on his daily commute. His radio operations can be followed at http://www.w1mj.com.