About this replacement
Barnes & Noble NOOK HD 7 (BNRV400 / BNTV400) — 3.7V Li-Polymer Replacement Battery (BNA-B0002)
This is a 3.7V 4000mAh lithium-polymer battery for the Barnes & Noble NOOK HD 7 tablet. It fits the BNRV400 and BNTV400 model numbers and replaces OEM part BNA-B0002 and L83-4977-266-01-4. Swap this in when the original cell no longer holds charge or the tablet shuts down unexpectedly under load.
- BNRV400 and BNTV400 compatibility: Both model codes refer to the same NOOK HD 7 hardware platform. They share an identical battery bay, connector pinout, and charge IC handshake, so one part number covers both.
- Bench tested on actual hardware: We cycled this cell through charge and discharge on the NOOK HD 7 platform. The BMS accepted the charge profile without fault codes, and voltage held steady across display-on and Wi-Fi-active load states.
- Fuel gauge reset after installation: After fitting this battery, run the tablet down to automatic shutoff, then charge uninterrupted to 100%. This forces the fuel gauge IC to recalibrate against the new cell and eliminates the inaccurate percentage readings that commonly appear after a swap.
NOOK HD 7 shutting down at 15–25% remaining
The NOOK HD 7 combines a power-hungry 7-inch IPS display with active Wi-Fi into a relatively narrow voltage window. When the cell ages, voltage sags faster than the fuel gauge tracks — the tablet reads 20% but the cell voltage has already dropped below the BMS cutoff threshold. This is a cell-level problem, not a software fault. Fitting a fresh 4000mAh cell restores the flat discharge curve and pushes the real cutoff back below 5%. After the swap, run one full recalibration cycle so the fuel gauge IC maps the new voltage curve correctly.
Tablet showing 100% charge but losing percentage within minutes of unplugging
This is fuel gauge drift — the charge IC is reporting state-of-charge based on a calibration curve built around the old, degraded cell. The new cell has a different internal resistance and capacity profile, so the reported percentage detaches from actual charge state almost immediately. It is not a fault in the replacement battery. Discharge the tablet completely to auto-shutoff, then charge in one uninterrupted session to 100% at the standard 5V USB rate — this resets the calibration and the percentage display will track correctly from that point.