Simvalley SP-140 Replacement Battery PX-3524 3.7V 1300mAh

Simvalley SP-140 / SingleCore — 3.7V Li-ion Replacement Battery (PX-3524)

This 3.7V 1300mAh (4.81Wh) Li-ion cell is a direct replacement for the Simvalley SP-140 and SingleCore smartphones. It matches the original OEM part number PX-3524 and fits the physical battery bay without modification. Install it when the original cell no longer holds a usable charge or fails to power the phone through a normal day.

• SP-140 and SingleCore compatibility: Both devices share the same battery bay dimensions, voltage rail, and connector pinout. The cell measures 65.05 × 55.10 × 4.50mm — the same footprint Simvalley used across this phone line. Swapping between variants does not require any adapter or rewiring.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the SP-140 platform. The BMS accepted the charge handshake without fault flags, held voltage above 3.5V through mid-discharge, and terminated cleanly at the low-voltage cutoff threshold.
• Fuel gauge recalibration on first cycle: After fitting the new cell, disable any fast-charge mode and run one full discharge-to-charge cycle before normal use. The SP-140 fuel gauge IC is calibrated to the original cell's discharge curve. One full cycle lets it remap against the new cell before the coulomb counter locks in its reference points.

Why the SP-140 reports wrong battery percentage after a cell swap

The SP-140 uses a fuel gauge IC that tracks charge state against a stored discharge curve from the original cell. When you fit a new cell, the IC still references the old curve — so percentage readings can be off by 15–25% until it recalibrates. 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 baseline to the new cell's actual capacity and voltage profile.

Sudden shutdown at 20–30% remaining on the SP-140

This happens when the cell voltage drops sharply under load — modem transmission or screen brightness spikes pull current the cell cannot sustain, and voltage collapses below the BMS cutoff threshold even though the gauge still reads 20–30%. It is a voltage-cliff problem, not a capacity problem. Confirm it by checking whether the phone shuts off during calls or screen-on use specifically. If the cell is new, one full calibration cycle usually corrects the gauge so the reported percentage matches the actual voltage curve at 3.55–3.60V cutoff.