About this replacement
Toshiba Chromebook CB35 Series — 10.8V Li-Polymer Replacement Battery (PA5208U-1BRS)
This 10.8V, 3850mAh (41.58Wh) lithium-polymer battery replaces the original cell in the Toshiba Chromebook CB35, CB35-B, CB35-B3340, and CB35-A3120. It uses OEM part number PA5208U-1BRS and P000619700. Install it when the existing cell no longer holds charge through a normal work session away from AC power.
- CB35 series fit: All CB35 variants share the same 10.8V battery rail, connector pinout, and BMS handshake protocol — that is why one cell covers the full CB35 lineup including the B3340 and A3120 sub-models.
- Bench tested on actual hardware: We cycled this cell through charge and discharge on a CB35 unit and verified the BMS negotiated correctly, reported state-of-charge accurately, and held voltage above the cutoff threshold under combined CPU and display load.
- First-cycle calibration on the CB35: After installing, run one full discharge until Chrome OS hibernates, then charge uninterrupted to 100% without interruption. This resets the BIOS battery learn cycle and clears the inaccurate health warning that appears after every cell swap on this platform.
Why the CB35 shuts down at 20–30% charge shown on screen
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 full CPU plus display load before the gauge reaches zero. Chrome OS reads the voltage drop as an immediate shutdown threshold rather than a low-battery warning. Running two full calibration cycles — full discharge to hibernate cutoff, then full uninterrupted charge — teaches the gauge IC the new cell's actual curve and eliminates the premature cutoff.
Chrome OS reporting battery Wh as wrong after swap
The Wh figure Chrome OS displays is read from EEPROM data embedded in the battery pack — not calculated live from voltage and current. If the replacement cell's EEPROM carries a different rated Wh than the original, the system info panel will show a mismatched number even though the physical capacity is correct. This is an EEPROM-rated versus actual-chemistry difference and does not affect charging or runtime. Verify the actual capacity is 41.58Wh against the product data — if it matches, the display discrepancy is cosmetic only.