About this replacement
Yaesu FT-25R / FT-65R / FTA-250L — 7.4V Li-ion Replacement Battery (FNB-26L)
This is a 7.4V, 2500mAh Li-ion battery pack built to the FNB-26L specification. It fits the Yaesu FT-25R, FT-65R, and FTA-250L handheld transceivers. All three radios share the same battery bay geometry, connector pinout, and BMS handshake protocol.
- FT-25R, FT-65R, and FTA-250L compatibility: These three radios run on the same 7.4V rail and use an identical battery latch and contact arrangement. Yaesu standardised the BMS communication across this platform, so one pack covers all three without modification.
- Bench tested on actual hardware: We ran this pack through full charge and discharge cycles on the FT-25R platform. The BMS handled PTT transmit spikes without tripping, held voltage above the radio's low-battery cutoff through sustained keying, and accepted a full charge cycle in the Yaesu desktop charger without fault indication.
- First-insertion contact check: If the charger dock shows a fault LED on first insertion, remove the pack and wipe the gold contact strip with a dry cloth before reseating firmly. The Yaesu dock requires a clean contact cycle to complete the BMS handshake before charging begins.
Why the FT-25R drops to reduced TX power mid-shift on a new pack
A new FNB-26L ships at storage voltage — typically around 3.7V per cell, not the 4.2V full-charge peak. When the radio draws transmit current from a partially charged pack, the voltage sags under load and the radio's power management steps down RF output to protect the finals. This is not a faulty cell. A full charge cycle before extended use brings both cells to 4.2V and eliminates the sag. Run the pack through one complete charge in the desktop charger before taking it out in the field.
Bar indicator shows one fewer bar than expected after inserting the FNB-26L
The FT-25R reads battery level by measuring pack voltage against fixed thresholds — it does not track charge state any other way. A new pack at storage voltage sits below the top threshold, so the display shows one bar short of full even though the pack is not depleted. This resolves completely after one full charge cycle. Once the pack reaches 8.4V at the terminals, the radio will read the correct bar level on next power-up.