About this replacement
Asus R2H / R2E / R2Hv — 7.4V Li-Polymer Replacement Battery (C22-R2)
This is a 7.4V, 6860mAh (50.76Wh) lithium-polymer replacement battery for the Asus R2H, R2E, and R2Hv convertible tablet PCs. It replaces OEM part numbers C22-R2, C21-R2, 90-NGV1B2000T, 90-NGV1B1000T, and 70-NGV1B4000M. These mid-2000s ultraportable tablets draw from a single battery pack to power the processor, display, touchscreen digitizer, and wireless peripherals simultaneously.
- R2H, R2E, and R2Hv compatibility: All three models share the same battery bay dimensions, connector pinout, and BMS communication protocol over the SMBus line. A single cell swap covers the full R2 platform without modification.
- Bench tested on actual hardware: We cycled this cell through full charge and discharge on the R2H platform. The BMS negotiated correctly over SMBus, charge termination triggered at the expected cutoff voltage, and the protection circuit tripped cleanly on over-discharge without locking the pack.
- First-cycle conditioning on the R2 platform: After installing this cell, run the device on battery until Windows triggers hibernate at the low-battery cutoff — do not interrupt it. Then charge uninterrupted to 100%. This forces the BIOS battery learn cycle to reset against the new cell's actual capacity and clears the inaccurate health warning that appears after every cell swap on this platform.
Why the R2H BIOS reports poor battery health immediately after a cell swap
The R2H stores learned capacity data in EEPROM on the battery's SMBus controller. When a new cell is installed, the BIOS reads stale EEPROM values that do not match the fresh cell's actual charge curve. The system flags this mismatch as degraded health before any real measurement has taken place. Running one complete discharge-to-hibernate followed by an uninterrupted full charge resets the learn cycle and writes accurate data back to the fuel gauge IC. After two to three full cycles the health readout stabilises.
R2H shutting down at 20–30% charge shown on the gauge
This happens when the fuel gauge IC is still calibrated to the old cell's discharge curve. The new cell hits a voltage cliff under combined CPU and display load that the uncalibrated gauge interprets as 20–30% remaining, but the pack is actually near depletion. It is not a fault with the replacement cell. Run two full discharge-to-hibernate cycles without interrupting the charge phase — the gauge recalibrates against the new chemistry and the shutdowns stop. If they persist past three cycles, check that the SMBus connection on the battery connector is fully seated and reading above 7.0V at idle.