About this replacement
Nest Connect — 3.7V Li-ion Replacement Battery (A3GT2001H)
This is a 3.7V 700mAh Li-ion battery for the Nest Connect (models A0078 and H17). The Nest Connect acts as a range-extending mesh node for Nest thermostats, smoke detectors, and compatible smart home devices. When the internal battery depletes, the Connect drops off the network and the devices that rely on it for range lose their cloud link.
- Nest Connect A0078 and H17 compatibility: Both hardware revisions use the same 3.7V single-cell Li-ion rail with identical connector orientation and BMS handshake protocol — one battery covers both.
- Bench tested on actual hardware: We ran this cell through charge and discharge cycles on a Connect unit. The BMS accepted the cell without fault codes, and the protection circuit tripped correctly at the low-voltage threshold before recovery.
- Network re-join after power interruption: After installing this battery, wait at least 60 seconds before checking connectivity. The Connect runs a mesh network re-join sequence every time power is interrupted — pulling the cell and reinserting it triggers the same sequence.
Why the Nest Connect goes offline after a battery swap
Swapping the battery cuts power to the Connect's radio module, which forces a full mesh re-initialisation on restart. The device broadcasts its network ID and waits for the Nest hub to acknowledge it before resuming normal relay operation. This handshake can take 30 to 90 seconds depending on hub load and signal conditions. If the device stays offline past two minutes, open the Nest app and check whether the Connect appears under Settings — it may need a manual re-pair.
New battery triggering a low-battery alert immediately
Li-ion cells lose charge during storage, and if the cell voltage has dropped below roughly 3.4V before installation, the Connect's firmware will flag it as low before the device finishes booting. The alert is voltage-based, not capacity-based, so the cell just needs a charge cycle to clear it. Plug the Connect into its wall adapter for at least two hours after fitting the new battery. Once the cell reaches its nominal 3.7V, the alert clears automatically in the Nest app.