Lux 500 Thermostat Battery Replacement Guide: Seamless Power Switch

Emily Jul 26, 2026

The Lux 500 thermostat, a sleek and energy-efficient addition to your smart home, is designed to provide convenience and precision. However, like any device with a battery, the Lux 500 may require a battery change at some point. In this guide, we'll walk you through the process step-by-step, ensuring a smooth and hassle-free experience.

Home Repairs - Lux Thermostats - How To Change Batteries? – Storables
Home Repairs - Lux Thermostats - How To Change Batteries? – Storables

Changing the battery in your Lux 500 thermostat might seem like a daunting task, but with the right pointers, it's actually quite simple. Let's dive into the details.

How to Set/Reset Lux/Luxpro Thermostat  - Ready To DIY
How to Set/Reset Lux/Luxpro Thermostat  - Ready To DIY

Identifying the Battery Issue

Before we dive into changing the battery, it's essential to confirm that the issue is indeed the battery and not some other technical hitch. Your Lux 500 thermostat will typically display an error message or a low battery icon when the battery is due for a change. However, if you're unsure, the first step is to reset your thermostat.

How To Fix The Lux Pro Thermostat's Low Battery?
How To Fix The Lux Pro Thermostat's Low Battery?

Resetting your Lux 500 involves simultaneously pressing and holding the 'System' and 'Menu' buttons for about 10 seconds. If the thermostat turns off and back on, and the issue persists, it's likely that the battery needs changing.

Gathering Your Tools

How to Change Batteries in a Honeywell Home Thermostat (6 Steps)
How to Change Batteries in a Honeywell Home Thermostat (6 Steps)

Once you've confirmed that it's the battery causing the issue, gather your tools. You'll need a flathead screwdriver and a fresh CR2032 battery, which is the standard size for Lux thermostats.

You can purchase CR2032 batteries from most hardware stores or online platforms. Ensure you buy a 3V lithium coin cell battery, as this is the compatible voltage for your Lux 500 thermostat.

Accessing the Battery Compartment

Honeywell; Thermostat; Batteries; Change; Replace; Remove; Cover
Honeywell; Thermostat; Batteries; Change; Replace; Remove; Cover

With your tools ready, the next step is to access the battery compartment. Start by removing the cover plate on the bottom left corner of your thermostat. You can do this using the flathead screwdriver. The cover plate is secured with small screws, so be careful not to strip them.

Once the cover plate is removed, you'll see a small trapdoor that conceals the battery. Use the flathead screwdriver to gently pry this door open. Now, you should be able to see the battery.

Removing and Replacing the Battery

TX500U Programmable 5/2-Day Thermostat with Selectable Smart Recovery, Universal Compatability, Battery-Powered or System-Powered
TX500U Programmable 5/2-Day Thermostat with Selectable Smart Recovery, Universal Compatability, Battery-Powered or System-Powered

With the battery compartment exposed, you can now proceed to remove the old battery. Once again, use the flathead screwdriver to gently lift the battery out by one of its edges. Be careful not to damage the battery or the contacts.

Before inserting the new battery, make sure the newer battery has the same voltage as the old one (3V). Also, ensure that the positive and negative sides of the battery are correctly aligned with the terminals in the compartment. The positive side (+) should be facing up.

thermostat
thermostat
thermostaer is mounted on the wall displaying 75 minutes
thermostaer is mounted on the wall displaying 75 minutes
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Reassembling and Testing the Thermostat

Once the new battery is in place, gently close the battery door and put the cover plate back on. Secure the cover plate using the screws you removed earlier.

Now, it's time to test your Lux 500 thermostat. Turn it back on and check if the low battery or error message has disappeared. Your thermostat should now be functioning as normal.

Preventive Maintenance Tips

Regular maintenance can help extend the life of your battery and prevent unexpected failures. Consider setting reminders to check your battery every six months. This will help you stay on top of things and prevent the last-minute rush to change the battery.

Moreover, ensure that your thermostat is not exposed to extreme temperatures, as these can also degrade the battery faster. Keep it at a moderate temperature for optimal battery life.

And there you have it! Changing the battery in your Lux 500 thermostat doesn't have to be a complex process. With these simple steps, you're well on your way to restoring your thermostat's optimal functioning. So, the next time you notice your thermostat behaving strangely, don't hesitate to check if a battery change is needed.