About this replacement
TP-Link C400S2 / C420S2 Series — 3.7V Li-ion Replacement Battery (HB-A100)
This is a 3.7V 7000mAh (25.9Wh) Li-ion replacement for the TP-Link HB-A100 battery cell. It fits the C400S2, C420S1, C420S2, and D230S1 wireless outdoor security cameras. Same voltage, same capacity, same connector as the original.
- C400S2 / C420 / D230 platform fit: These models share the same battery bay geometry, connector pin-out, and BMS handshake protocol — so one cell covers all three lines without any modification.
- Bench tested on actual hardware: We cycled this cell through motion-trigger events and sustained IR night-vision draws. The BMS held charge delivery stable across both load profiles without tripping into protective cutoff.
- First-install power cycle: After inserting the battery, power cycle the camera once through the Tapo app. The firmware must register the new cell before motion events log correctly to cloud storage — skipping this step can cause missed clips on first trigger.
App showing 0% or incorrect charge percentage after battery swap
The C400S2 reads charge level using a voltage-threshold indicator, not a fuel gauge IC. When a new cell is installed, the camera's firmware hasn't calibrated the resting voltage to a percentage yet. The display will show 0% or a frozen number until the battery goes through one full charge cycle. Plug in the charging cable, let it run to full, then disconnect — the percentage should update correctly within a few minutes of reconnection to the app.
Camera goes offline in the Tapo app after battery replacement
Swapping the battery clears the camera's active session token, which the Tapo app uses to maintain the live connection. The camera reboots with a new session but the app still holds the old one, so it registers the device as offline. Open the Tapo app, navigate to the device settings, and tap the reconnect or re-register option to force a fresh handshake. If the camera still shows offline after that, hold the reset button for five seconds and re-add it through the app as a new device.