TP-Link Neffos C7s Replacement Battery 3.8V 2500mAh NBL-43A2500

TP-Link Neffos C7s — 3.8V Li-ion Replacement Battery (NBL-43A2500)

This is a 3.8V, 2500mAh (9.5Wh) Li-ion replacement battery for the TP-Link Neffos C7s smartphone, covering model variants TP7051A and TP7051C. It matches the OEM part number NBL-43A2500 and fits the original battery bay without modification. Use this to restore charge capacity when the original cell has degraded past the point of useful daily use.

• Neffos C7s variants (TP7051A, TP7051C): Both variants run the same 3.8V rail, use the same connector pinout, and communicate with the same fuel gauge IC — this cell slots into either board without conflict.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on a Neffos C7s board. The BMS accepted the cell without a protection trip, and the charge IC engaged correctly at both standard and fast-charge current levels.
• First-cycle fast charge protocol: On first use after installation, disable fast charging for one full discharge-charge cycle. The fuel gauge IC needs to map the new cell's discharge curve before high-current charging pushes into an uncalibrated state — skipping this causes percentage drift for the first several cycles.

Why the Neffos C7s reports wrong battery percentage after a cell swap

The fuel gauge IC on the C7s board stores a learned discharge curve from the original cell. When a new cell goes in, that stored curve no longer matches actual cell chemistry, so the IC reports inaccurate state-of-charge values — often reading 10–20% higher or lower than reality. The fix is one complete discharge down to automatic shutdown, followed by a full uninterrupted charge to 100%. After that cycle, the coulomb counter resets its reference points against the new cell and percentage reporting stabilises.

Sudden shutdown at 20–30% on the replacement cell

This happens when the cell voltage drops below the BMS cutoff threshold under load — typically during simultaneous screen-on and mobile data activity — even though the OS reports remaining charge. A fresh Li-ion cell has a steeper voltage cliff than a broken-in one, so the BMS trips before the fuel gauge catches up. Run two full discharge-charge cycles without fast charging to let the cell's internal resistance stabilise. After break-in, the voltage under load at 20–30% should stay above the 3.2V BMS cutoff threshold and shutdowns stop.