Tatung TNB-5500 Replacement Battery 10.8V 6600mAh DR202

Tatung TNB-5500 / TNB-5600 — 10.8V Li-ion Replacement Battery (DR202)

This is a 10.8V, 6600mAh (71.28Wh) lithium-ion battery for the Tatung TNB-5500 and TNB-5600 notebooks. It replaces OEM part numbers DR202, EMC36, ME202BB, NL2020, and SMP02. Install it when the original cell no longer holds a charge or causes unexpected shutdowns.

• TNB-5500 and TNB-5600 compatibility: Both models share the same 10.8V battery rail, connector pinout, and BMS handshake protocol — one cell covers both. The BMS on each communicates via the same SMBus line, so the EEPROM exchange at first boot works identically across both platforms.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the TNB platform and confirmed the BMS completed its handshake without fault codes. The cell held 10.8V nominal throughout the discharge curve and accepted a full charge without throttling.
• Post-install calibration on the TNB-5500: After fitting this cell, run a full discharge down to hibernate-cutoff, then charge uninterrupted to 100%. This resets the BIOS battery learn cycle and clears the inaccurate health warning that appears after a cell swap — skipping this step leaves the fuel gauge IC reading against the old cell's EEPROM data.

Why the TNB-5500 shuts down at 20–30% charge remaining

The TNB-5500's fuel gauge IC calibrates its low-voltage cutoff against the previous cell's discharge curve stored in EEPROM. When you swap in a new cell, the old curve still governs when the system triggers shutdown. The laptop's power management sees voltage drop under combined CPU and display load and acts on stale data — pulling the plug well above actual depletion. Running one full discharge-to-hibernate cycle rewrites the curve and aligns the cutoff to the new cell's actual voltage floor.

BIOS reporting battery health as "poor" or "replace soon" after installation

This warning is triggered by EEPROM data carried over from the worn cell, not by a fault in the new battery. The BIOS reads cycle count, rated capacity, and health flags written by the old cell's BMS — those figures follow the socket, not the chemistry. Complete one full discharge-to-hibernate cycle followed by an uninterrupted charge to 100%. After that cycle completes, the health flag should clear; if the warning persists, confirm the BIOS has the latest firmware, as some early TNB builds require a firmware update to re-read battery EEPROM correctly.