i-Blue 820 GPS Navigator Replacement Battery 3.7V 770mAh

i-Blue 820 / 821 GPS Navigator — 3.7V Li-ion Replacement Battery (HX-NBP6MC-G)

This is a 3.7V, 770mAh Li-ion replacement battery for the i-Blue 820 and 821 handheld GPS navigators. It matches the OEM HX-NBP6MC-G specification and fits the compact cell bay on both units. Swap it in when the original cell no longer holds a charge or the device shuts off unexpectedly during navigation.

• 820 and 821 shared cell platform: Both models use the same 3.7V cell bay, connector pinout, and BMS handshake. The same 40.20 × 40.90 × 6.50mm form factor covers both units without modification.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the 820 platform. The BMS held cutoff voltage correctly and the GPS receiver powered through without a reset fault.
• First-fix cold start after swap: After fitting this cell, power the unit on outdoors and leave it stationary. The GPS performs a full cold start after any complete power interruption — first satellite acquisition can take 5–10 minutes. Subsequent warm starts drop back under a minute once almanac data is cached.

GPS accuracy dropping off as the i-Blue 820 battery gets low

At reduced cell voltage, the i-Blue 820 scales back receiver sensitivity to protect remaining power headroom. The GPS antenna and signal processor draw more current than any other component on the board. When the cell sags below roughly 3.5V under load, the unit compensates by reducing receiver gain — position accuracy degrades before the low-battery indicator triggers. A fresh cell at full charge restores the receiver to full sensitivity immediately.

Saved routes and waypoints missing after battery replacement

The i-Blue 820 stores active route and waypoint data in battery-backed RAM. When the cell is fully removed, that volatile memory loses power and the stored data clears. This is not a firmware fault — it is a consequence of complete power interruption. Before swapping the battery, export your routes via the companion software. Reload them from the backup file after the new cell is fitted and the unit boots clean.