Decreasing battery voltage

[Charles9]

I have a Nest Learning Thermostat 3rd generation in my garage set to keep it at 40-45°F. It's connected to a TACO multi-zone system. Heat-only Modine radiator setup with Rh and W1 wires . No C wire. The Voc and Vin both read ~33-35. The lin reads 40 mA.

It shuts off motion/proximity sending and reads low battery on its Nest App screen. The battery voltage is slowly dropping through the 6 range. Why the low battery voltage with normal Voc, Vin, and Lin readings? Is the performance of the internal rechargeable lithium battery compromised by an ambient temperature of 45°?

 

 

 

[Markjosephp · Accepted solution]

Hello Charles9,

Thanks for posting your detailed information about your Nest Learning Thermostat setup in your garage. The low battery issue, despite normal Voc, Vin, and Lin readings, might be related to the ambient temperature in the garage.

The built-in battery in your Nest Thermostat, can be affected by extreme temperatures. Cold temperatures, such as 45°F in your garage, can reduce the efficiency of the internal battery. It may not be able to deliver the required voltage consistently, leading to low battery warnings and shutdowns.

You might want to consider a few things:

• Confirm if the low battery issue coincides with the drop in ambient temperature. If so, it's likely that the cold environment is affecting the battery's performance.
• Ensure that the thermostat is adequately insulated, or consider adding insulation around it to provide some protection against the cold.
• Since you don't have a C wire, the Nest Thermostat relies on its internal battery. If the battery is struggling in the cold, you might need to explore alternative power options or address the insulation issue, and that means installing a C wire or a Nest Power Connector to constantly deliver enough power to it.

Let us know if you have more questions.

Best regards,
Mark

[Charles9]

Hi Mark,

Thank you for your insightful response. The colder the ambient temperature, the worse the problem. The Nest Power Connector proved it is not a C wire equivalent by failing to support the thermostat, and replacing it with a resistor was marginally better.

Insulating the thermostat is impracticable.

It took me four months to suspect the problem was due to lithium battery chemistry. Google Nest Support agents neither suggested the problem or would answer my direct questions about it.

Some of my other Nest Learning Thermostats failed for other reasons. My experience with Google Nest Support over four months was consistently poor. The unreliability of the thermostats and the weakness of their support have forced me to abandon them.

Sincerely,

Charles

[Markjosephp]

Hey there,

I understand that enduring such challenges for four months can be frustrating, and the decision to move away from Nest Thermostats is undoubtedly a significant one. We deeply appreciate you sharing your thoughts and experiences, and we'll take it as feedback.

If you have found an alternative that better meets your needs, I hope it provides the reliability and support you deserve. If there's anything specific you'd like assistance with or if you have further questions, feel free to share, and I'll do my best to help.

Warm regards,
Mark