Casio V-T500 Replacement Battery HA-M20BAT 3.7V 9500mAh

Casio V-T500 — 3.7V Li-Polymer Replacement Battery (HA-M20BAT)

This is a 3.7V, 9500mAh lithium-polymer replacement battery for the Casio V-T500 tablet. It carries OEM part number HA-M20BAT and fits the V-T500 directly. At 35.15Wh, it matches the original cell's energy spec and connects to the same BMS interface on the mainboard.

• V-T500 platform fit: The V-T500 uses a single-cell Li-Po architecture with a dedicated fuel gauge IC on the battery's protection circuit. The HA-M20BAT connector and BMS handshake are specific to this board — other Casio tablet batteries won't seat or communicate correctly here.
• Bench tested on actual hardware: We cycled this cell through the V-T500's charge controller and confirmed the BMS accepted the cell, reported state-of-charge correctly after one full cycle, and held voltage above 3.5V under sustained display-plus-WiFi load.
• Fuel gauge IC reset after installation: After fitting this battery, run one full discharge to automatic shutoff, then charge uninterrupted to 100%. This forces the V-T500's fuel gauge IC to recalibrate against the new cell and clears the inaccurate percentage readings that almost always appear after a swap.

Why the V-T500 shuts down between 15–25% after a battery swap

The V-T500 uses a coulomb-counting fuel gauge IC that was calibrated to the old, degraded cell. When a new cell arrives, its voltage curve doesn't match the stored calibration data. Under combined load — backlight, WiFi radio, and active apps — the device pulls enough current to trigger a rapid voltage drop at the bottom of the charge curve. The BMS interprets this as a critical undervoltage event and shuts the tablet down even though charge remains. One full discharge-to-shutoff cycle followed by an uninterrupted charge to 100% resets this calibration.

Fast charging not available on the V-T500 after battery replacement

The V-T500's charge IC runs a handshake with the charger during the first accepted charge cycle. If the battery was replaced and the tablet hasn't completed a full charge yet, the system may default to trickle or standard charge rates as a precaution. This isn't a fault with the cell — it's the charge controller resetting its negotiation state. Plug into the original Casio charger or a USB-PD source rated at the correct voltage, let the first charge run to 100% without interruption, and fast charge availability will restore on subsequent cycles.