Changing the Backup Battery for Your Smith Thompson Home Security System

You’ve noticed an illuminated trouble light on your Smith Thompson Home Security system alarm panel. In many cases, this indicator is the sign that your system’s backup battery needs replacement. This guide will explain how to replace the battery without calling a service technician.

Why Replacing Your Battery Is Important

Before we delve into the step-by-step process for replacing your security system’s backup battery, let’s first talk briefly about why replacing this battery is important for keeping your system up and running.

As you probably know, your security system operates on AC power most of the time. So long as your home has power, the security system will not need to draw any power from the backup battery. Where your backup battery becomes vital, though, is in filling in the gaps when you don’t have electricity. The battery will keep your alarm system up and running—and your home secure—even during power outages. Said another way, think of the lead-sealed backup battery in your system alarm box as a failsafe for the system as a whole.

How to Know When to Replace the Battery

The good news is that you won’t need to change your backup battery very regularly. In part, because these batteries are not the primary power source for your security system, they tend to last a long time. 3-5 years is a commonly cited lifespan for lead-sealed batteries, and they might even last longer.

Luckily, you won’t need to guess. If and when your battery starts to die, your system will alert you that it needs replacement. As mentioned at the beginning of this article, you will notice a trouble light illuminated on your Smith Thompson alarm panel. This indicator tells you when the battery is too weak to provide reliable backup power for your system.

How to Replace Your Battery

If you need to replace your backup battery, the first step will be to purchase a replacement battery that matches the one currently installed in your alarm box. The type of battery we use for our home security systems is a universal 12-volt, 5-amp-hour UB1250 battery. Smith Thompson can mail you a replacement battery for a small cost, or you can purchase one at your local RadioShack, Batteries Plus, or preferred hardware store. You can also find these batteries online, on and other sites. These batteries are typically very affordable: you shouldn’t expect to pay more than $20 for your replacement UB1250 battery.

To replace your alarm system backup battery, go to your closet (or wherever your metal alarm box is situated) and open the box. In some cases, the alarm door will be screwed shut. You can get the box open by unscrewing the screw on the right side of the box.

Note that all the wires in your alarm box are low voltage. There is no risk of being shocked while working with the wires or replacing your battery. These factors make this project easy as a do-it-yourself venture.

In the bottom of the box, you will see a large black battery, approximately the size of your fist. The battery will be labeled “UB1250: Universal Batteries” in large white lettering and will have both red and black wires connected to matching terminals on the top. You will need to remove these wires, one at a time before you can remove and replace the battery.

To remove the batteries, start with the red (positive) wire on the left side of the battery. Pull and wiggle the wire at the terminal to release it from the battery. Next, repeat the same process for the black (negative) wire on the right side of the battery. Once both wires are disconnected, you should be able to pull the battery out of the alarm box quite easily.

Set the old battery aside and place the new battery into the alarm box, in the exact same spot where the old battery was situated. Connect the wires to their matching battery terminals, starting with the red positive wire and concluding with the black negative wire. Be careful to plug the red positive wire into the red positive terminal and the black negative wire into the black negative terminal. Mixing up the wires (e.g. connecting black to red or red to black) can damage your system.

Once the new battery is installed and connected, close the door on your metal alarm box. If you removed a screw when opening the box, replace the screw now.

Ideally, the trouble light on your system keypad will no longer be illuminated. Sometimes, though, it can take the system a few moments to register the installation of a new battery. Your trouble light should reset within 30 minutes. If the trouble light still illuminates after more than 30 minutes, you should call the Smith Thompson service department for assistance and troubleshooting.

Replacing your backup battery when it reaches the end of its life is a vital step to make sure that your security system of choice is capable of protecting your home no matter what happens. Following the steps laid out above make it easy to carry out this project on a DIY basis in a matter of several minutes. If you have any questions, or if you would like Smith Thompson to send you a replacement battery, feel free to contact us directly.

Family Owned Dallas Home Security Company Since 1978

We are the largest independent alarm company in Texas, family owned and operated since 1978. Two generations of family are on the job, and now offering multiple home services.

No Contracts. No Price Increases.

Get a Quote today!

  • One of our dedicated support team will contact you to customize a solution just for you.
  • This field is for validation purposes and should be left unchanged.

What our customers say

100% Satisfied

From the first phone call to the actual use of our security system we have been 100% satisfied! The technician was knowledgeable and courteous. He was able to answer all my questions and get the system up and running in no time. Thank you Smith Thompson Home Security for making our home more secure and at an affordable price to do so!!!!

Happy Customer Dallas, TX

We had a great experience with Smith Thompson

Recently for our home in downtown Houston! I was referred to Smith Thompson by a friend after expressing frustration with some of the larger brands that lock you into a 3-year contract. We called to inquire about the most cost-effective…

Excited Customer Houston, Texas
As Seen On
As Heard On

We've had the same 16.95 rate for 45 years!