Batteries are the most common way of powering equipment not connected to the electric grid--making this topic of vital interest to nearly every ham.  The care and feeding of batteries is a very popular topic, not just among hams, but nearly everyone these days.

• Batteries for the Elecraft KX3 and other Low Power Radios
  QST March 2020 pp. 38-40
• A Battery-Voltage Indicator 
  QST October 1998, pp. 50-51
  Here's a quick and inexpensive project that allows you to keep tabs on your gel cell.
• Honey, They've Shrunk the Batteries!
  QST December 2001, pp. 31-35
  A rundown on popular batteries, their uses, characteristics and care.