TP-Link Neffos C9 Max NBL-40A2950 Compatible Battery 3.85V 2850mAh

TP-Link Neffos C9 Max / TP7062 — 3.85V Li-Polymer Replacement Battery (NBL-40A2950)

This is a 3.85V, 2850mAh Li-Polymer cell for the TP-Link Neffos C9 Max (model TP7062). It replaces the original NBL-40A2950 battery when the factory cell no longer holds charge or fails to power the phone. Dimensions are 77.90 × 59.20 × 4.00mm — verify against your existing cell before fitting.

• Neffos C9 Max / TP7062 fit: Both model references share the same chassis dimensions, connector pinout, and charge IC handshake. One cell covers both variants without any modification.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the bench, confirming BMS cutoff triggers correctly at low voltage and that the charge IC accepts the cell without flagging an incompatible battery error.
• Fuel gauge recalibration after swap: On first use after installation, disable fast charging and run one complete discharge-to-charge cycle at standard current. This lets the fuel gauge IC map the new cell's discharge curve before the coulomb counter locks in its reference points.

Sudden shutdown at 20–30% on the Neffos C9 Max after a cell replacement

A fresh Li-Polymer cell has a slightly different voltage-versus-capacity curve than the aged cell the fuel gauge IC was trained on. When the phone hits a high-draw moment — mobile data handoff, screen at full brightness, GPS active — the new cell's voltage dips sharply below the threshold the IC expects at that reported percentage. Android interprets this as a critical voltage event and forces a shutdown before the display reads zero. One full discharge-charge cycle at standard current recalibrates the coulomb counter to the new curve and the shutdowns stop.

USB charging not detected after fitting the NBL-40A2950 replacement

If the Neffos C9 Max shows no charging indicator after a battery swap, the BMS on the new cell may be in a locked state from storage at low voltage. Connect the phone to a 5V/1A charger — not a fast charger — and leave it for 15–20 minutes without pressing the power button. The charge IC sends a trickle current that nudges the cell voltage above the BMS unlock threshold, typically around 2.8–3.0V per cell, after which normal charging resumes. If the screen stays dark throughout, check that the battery connector is fully seated and the locking tab is clicked down flat.