Series LI · Drop-in lithium
Twice the range,
half the charge time.
The LI-81XB is a drop-in 18650 lithium-ion battery pack engineered for the Yaesu FT-817, FT-817ND and FT-818ND. Full-rated TX power, every band, every charge.
- Capacity
- 3200mAh
- Voltage
- 11.1V
- Charge
- 2.25h
Performance at a glance
Why upgrade
Engineered for real-world field use.
01
More than 2× the energy
Stock FNB-85 delivers 13–14 Wh of usable energy. The LI-81XB delivers ≈ 35.5 Wh — a 2.5× improvement.
02
Full-rated TX power
11.1 V nominal keeps the transceiver inside its preferred input window — full 5 W (FT-817) or 6 W (FT-818ND) on every band.
03
Massive discharge headroom
BMS rated for 10 A continuous — over 5× the radio's peak demand. No sag-induced dropout under long CW or digital transmissions.
04
Dramatically faster charging
External 5.5 × 2.1 mm jack routes 12.6 V directly to the BMS. Full pack in 2–3 hours, with per-cell over-voltage cut-off. The charger's indicator light shows red while charging is in progress and turns green when the charge cycle is complete.
Technical specifications
Every spec, line by line.
| Chemistry & cells | |
| Chemistry | Lithium-Ion (18650, 3S1P) |
|---|---|
| Cell rating | 3.7 V nom, 3200 mAh × 3 |
| Cell type required | 18650 button-top (positive stud); protected or unprotected |
| Electrical | |
| Nominal pack voltage | 11.1V |
| Voltage range (full → cut-off) | 12.6 → 9.0V |
| Rated pack capacity | 3200 mAh (≈ 35.5 Wh) |
| Continuous discharge (BMS limit) | 10A |
| Typical TX current @ 5 W out | ≈ 1.9A |
| Discharge headroom | > 5× radio peak draw |
| Protection & charging | |
| BMS protection | Per-cell OV / UV / OC / SC |
| Charging | External 5.5 × 2.1 mm DC jack, 12.6 V |
| Charge time (typical) | 2–3h |
| Cycle life | ≥ 500 cycles |
| Internal charging via radio | Must not be used (see §05) |
| Mechanical | |
| Form factor | Drop-in, FNB-72/85 footprint |
Configure & order
LI-81XB Lithium-Ion Battery Pack
3S 18650 architecture with integrated BMS, external charging port, and full-rated TX power on every band.
Secure checkout via Stripe. Shipping address collected at checkout (UK only).