This is the Ultimate Battery Backer from Electronic Model Systems. New $37.49 (37% off). This is a device which switches between main and auxiliary battery packs depending on the voltage difference between them. Features: * Works with 4 or 5 Cell NiCD packs.. * Works with 6Volt Gel-Cell or Lead Acid batteries.. * Universal connector works with Hitech, Futaba, and Z connectors.. * Main and backup batteries must be the same number of cells and th same voltage.. * Capacity of the two packs is not required to be the same.. * Simple wiring and installation. * Optional remote backup indication. * Optional inflight backup indication. * 60 Amp MOSFET devices used as battery switches.. * MOSFET device ON

This is Jomar Products Battery Backer for Futaba J radio systems. New $37.79 (36% off). This hooks between your receiver and dual batteries, and will activate your second battery if you lose voltage in the first one.:. Features: * Best insurance for fliers using two receiver packs..:. * When main battery drops, this will automatically switch to th second battery..:. * Works well with 4 cell, 5 cell, or Gel-Cell packs..:. * Batteries can be different capacities, such as, 1200 and 600mAh..:. * Warranty: Electronic Model Systems guarantees this Jomar product t be free of defects in materials or workmanship for a period of on year from date of purchase..:.