Samsung SGH-N500 Replacement Battery 3.7V 850mAh Li-ion

Samsung SGH-N500 / SGH-N508 — 3.7V Li-ion Replacement Battery

This is a 3.7V, 850mAh (3.15Wh) Li-ion cell for the Samsung SGH-N500 and SGH-N508 mobile phones. Both handsets use the same battery bay, connector, and charge IC, so a single cell covers both models. Fit this when the original cell no longer holds a usable charge through a normal day of calls and messaging.

• SGH-N500 and SGH-N508 compatibility: Both models share an identical battery bay geometry, three-pin connector layout, and charge IC communication protocol. The same cell works in either handset without modification.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the SGH-N500 platform. The BMS accepted the charge handshake on the first cycle, and the protection circuit tripped correctly at the low-voltage cutoff threshold — no runaway, no false cutoff above 3.0V.
• Fuel gauge recalibration on first use: After installation, run one full discharge to auto-shutoff followed by a complete uninterrupted charge to 100% before using the phone normally. The SGH-N500's fuel gauge IC maps its percentage table against that first full cycle — skipping it causes erratic percentage readings from day one.

Why the SGH-N500 reports wrong battery percentage after a cell swap

The SGH-N500 uses a coulomb-counting fuel gauge IC that stores a discharge curve calibrated to the original cell. When a new cell goes in, that stored curve no longer matches the actual voltage-versus-capacity relationship of the replacement. The gauge reads voltage and translates it using the old map, so it can show 40% when the cell is nearly empty. One complete discharge-to-shutoff and full recharge resets the coulomb counter baseline against the new cell's actual curve. After that cycle, percentage readouts stabilise.

Sudden shutdown at 20–30% on the replacement cell

This happens when the cell voltage drops sharply under the load spike from the GSM transmitter firing at full power during a call. The fuel gauge shows 25% remaining, but the cell's actual terminal voltage collapses below the 3.0V protection threshold under that burst current, and the BMS cuts the output. It is a voltage-sag issue, not a capacity issue. Let the phone complete the first full calibration cycle described above — if shutdowns persist after that, confirm the battery contacts are clean and making firm contact, as high contact resistance amplifies voltage sag.