Radio Shack 21-1926 Two-Way Radio Replacement Battery 4.8V 600mAh

Radio Shack 21-1926 — 4.8V Ni-MH Replacement Battery

This is a 4.8V, 600mAh Ni-MH battery built to the Radio Shack OEM part number 21-1926. It fits compatible Radio Shack handheld two-way radio units that use the original 21-1926 pack. Voltage and cell count match the original specification exactly.

• 21-1926 platform fit: Radio Shack packaged several handheld two-way radios around this 4.8V four-cell Ni-MH configuration. The connector pinout, cell count, and BMS handshake requirements are consistent across units that shipped with the 21-1926 pack, so one replacement covers the range.
• Bench tested on actual hardware: We cycled this pack through charge, standby, and transmit-load draws. The BMS held stable through PTT spikes — no overcurrent trip on keying, and cell balance stayed within spec across all four cells after three full cycles.
• First-insertion contact check: Ni-MH packs leaving storage can sit below the dock's acceptance threshold. If the charger shows a fault on first insertion, remove the pack, wipe the contact pads with a dry cloth, and reseat firmly. This clears the contact resistance the dock reads before it will begin the charge cycle.

Why the 21-1926 radio cuts out mid-transmission on a new pack

A fresh Ni-MH cell ships at storage voltage — typically around 1.0–1.1V per cell, putting a four-cell pack near 4.2–4.4V rather than the nominal 4.8V. When PTT is pressed, transmit current draw pulls that voltage down further. The radio's undervoltage circuit reads this as a depleted pack and cuts TX before the first charge is complete. Run at least one full charge cycle before using the radio on transmit. After that first cycle, mid-transmission dropouts caused by storage voltage disappear.

Bar indicator showing one fewer bar than expected after a full charge

Radio Shack two-way radios use simple voltage-threshold bar indicators — each bar maps to a fixed voltage window, not a fuel gauge chip. A new Ni-MH pack often peaks slightly below its rated voltage on the first charge cycle because the cells haven't fully formed yet. After two or three full charge-and-discharge cycles, resting cell voltage settles at nominal 1.2V per cell, bringing the pack to a solid 4.8V. At that point the indicator should read correctly — if it still shows one bar low after three cycles, measure pack voltage at the contacts; it should read 4.7V or above at rest.