Polytron R3500 Replacement Battery PL-7T6 3.7V 2000mAh

Polytron R3500 — 3.7V Li-ion Replacement Battery (PL-7T6)

This is a 3.7V, 2000mAh Li-ion cell built to fit the Polytron R3500 smartphone. It replaces OEM part number PL-7T6 directly. Slot dimensions are 70.18 x 60.00 x 4.67mm — measure your bay before ordering if the phone has been repaired before.

• R3500 fitment: The R3500 uses a single-cell 3.7V nominal architecture with a dedicated fuel gauge IC that tracks coulomb counts against the cell's discharge curve. Swapping to a matched 2000mAh cell keeps that IC within calibration range from the first cycle.
• Bench tested on actual hardware: We ran charge and discharge cycles on this cell and confirmed the BMS holds the charge termination voltage at 4.2V and trips the low-voltage cutoff before the cell drops below 3.0V under load — consistent with R3500 controller behaviour.
• First-cycle fuel gauge recalibration: On first use after installation, disable fast charging and run one full discharge-to-charge cycle at standard rate. This gives the fuel gauge IC time to map the new cell's discharge curve before high-current charging pushes current into an uncalibrated state.

Sudden shutdown at 20–30% on the replacement cell

This happens when the R3500's fuel gauge IC is still calibrated to the old, degraded cell's discharge curve. The new cell has a steeper voltage cliff under modem and screen load than the worn cell ever showed — so the phone's reported percentage is wrong, and the hardware cuts out before the OS can react. Running one complete discharge down to automatic shutdown, then charging uninterrupted to 100%, forces the coulomb counter to resync to the new cell's actual capacity. After that cycle, shutdowns at 20–30% typically stop.

Phone feels warm near the battery bay on first charge

A new cell arrives with higher internal impedance than a broken-in cell. The charge IC on the R3500 pushes current at its standard rate regardless, and the extra resistance converts some energy to heat. This is normal for the first two or three charge cycles as the cell's impedance settles. If the back of the phone is hot enough to be uncomfortable — not just warm — disconnect and let it cool before resuming. By cycle three, surface temperature during charging should drop noticeably.