Digital Thermometer Battery Change Explained

Ever wondered how a thermometer battery could make a difference to the digital thermometers of today? Mercury thermometers have been around for quite some time. However, digital thermometers began taking over not too long ago and have left mercury thermometers in the dust.

This part is for those buffs who like getting into the ‘WHY’ of things. If you’re not one of them skip down. But why was mercury used in a thermometer initially? For a simple reason that mercury is in a liquid state at room temperature. Secondly, mercury is used in thermometers because it has a high coefficient of expansion. Hence, the slightest change in temperature is detected when it is used in a thermometer. In addition to this, it has a high boiling point that makes it very suitable to measure higher temperatures.

Fun fact: did you know that each mercury thermometer contains about 1-1.5 grams of mercury? Mercury isn’t the friendliest of substances and is potentially dangerous if the thermometer glass breaks. Mercury can contaminate the surrounding air and become toxic to the family members. SAFETY FIRST. On the other hand, digital thermometers have several advantages over the mercury thermometers. As a matter of fact, a digital thermometer doesn’t rely on alcohol or water for its readings. Instead, digital thermometers contain metal parts that react on voltage to provide faster and more accurate results. Now, let us dive into the batteries of a digital thermometer and it’s replacement.

How Long Does a Thermometer Battery Last?

A good starting point is knowing how long you can expect your thermometer battery to last. There are a few factors on which the life of the thermometer battery depends. Thermometers use different kinds of batteries including but not limited to pencil cells, watch cells, and round cell batteries that can typically last for about 2,000 to 3,000 measurements. As a matter of fact, the maximum storage time is 3 to 5 years, although you will not complete 2,000 measurements even with a family size of 10.

You need to account for standby time, which drains the battery. If you take a maximum of 5 to 10 measurements per week at home. Then the battery will last for over 5 years in terms of the maximum number of measurements. Thus we can predict 3 to 5 years lifetime for thermometers used at home. On the other hand, if a thermometer is used in the hospital. There’s a possibility of using it 5 to 10 times a day. In this case, the battery may last for 1 to 1.5 years. Below is an example of a round button cell battery.

Thermometer battery

Power Management of a Digital Thermometer

Generally, probe type thermometers, use a coin-cell battery or two button cell batteries. Further, ear type thermometers usually use a coin cell battery or 2 AAA alkaline batteries. Both the thermometer types can run either directly from the battery or from a step-up switching regulator. This depends on the circuitry chosen. Some of the forehead-type thermometers use 9V transistor batteries, these look like mini rectangular canisters that have two heads on the top. (picture below)

Low shutdown current and turning the switching regulator off when not in use are critical in prolonging your batteries life. Sometimes, the battery falls below the microcontroller’s safe operating voltage. At this point, the thermometer will warn you that the battery will need to be replaced soon.

When Do You Need To Change the Thermometer Battery?

If the digital thermometer is for home use, then you need not worry about changing the battery often. This is because the installed battery will last for 3 to 5 years. But, if the thermometer is used in a hospital, then you need to change the batteries often. Consider purchasing a digital thermometer with an auto shut function. This will go off on its own when it is done taking the temperature reading. This conserves the battery and keeps it going for a long time. Many low-cost digital thermometers use batteries that are very difficult to find. Besides this, the batteries die out unexpectedly soon. Unfortunately, you need to throw the thermometer out in this case when the batteries die as they cannot be replaced.

Thermometer battery replacement

One of the reasons is as stated above that these batteries are very difficult to find. The second reason is that you may purchase replacement batteries online. But the fact is that they are as expensive as a brand new thermometer. It does not make sense to purchase thermometer batteries that are as expensive as a thermometer. Never compromise on quality. It is better to identify value over cost and purchase an efficient thermometer that gives you accurate results. Purchasing a thermometer without getting swayed by an extremely low price will go a long way.

Low Battery and Low Temperature: Don’t Confuse the Two


If the thermometer shows LO, this doesn’t mean that the battery is low. This indicates that the temperature is low. There’s a reason why the thermometer shows LO from time to time. It is because the room temperature is roughly 71.6 degrees Fahrenheit / 22 degrees Celcius. This temperature is too low for our digital thermometer. A digital thermometer can only measure down to 89.6 degrees Fahrenheit / 32 degrees Celcius. In such cases do not jump to replace your battery.

Low Temperature Reading in a Digital Thermometer

Here are some ways you can avoid the thermometer showing LO. First and foremost, ensure your mouth is shut tightly around the thermometer while using it, or lodged safely under your armpit. Secondly, ensure you place the thermometer as far back as possible in your mouth. The thermometer will give you accurate temperature readings if you do so. Another way is to place the thermometer underneath your tongue or right at its root.

Types of Batteries Used in a Thermometer

With normal use, the battery lasts a long time. However, if the battery symbol is blinking, this is an indication that you need to change the battery. Secondly, if the thermometer no longer starts or if it doesn’t give the beep sound anymore. This is another indication. So, if you need a new battery, it is recommended to ask for an ‘SR41’ round cell battery. In this type of batteries, 41 is the code for the battery size. ‘LR’ batteries are also suitable but they have a little shorter life as compared to the ‘SR41’ batteries.

Energizer Digital Thermometer Battery

Some thermometers require the Duracell AA batteries. One of the digital thermometers using this is the Braun Thermoscan ear thermometer. It is always better to carry the old battery with you, to avoid confusion. This will help you in purchasing the right one. Some thermometers have an extra battery option for quick replacements. This option enables you to replace the batteries in case they run out. It is handy when you don’t have time to run and buy other batteries urgently.

Replacing Digital Thermometer Batteries

Firstly, remove the battery compartment cover. Secondly, use an insulated probe to remove the battery. Even a toothpick can help you get the job done. Insert a new battery most likely an (LR41) with the + pole facing upwards. As mentioned earlier, the battery to be replaced differs from thermometer to thermometer. After this, reattach the battery compartment cover. Lastly, don’t forget to dispose of the empty battery in a proper way. Keep children away from these batteries as swallowing the battery could be harmful or, in some cases even, fatal.

The best thermometer is one which gives you accurate readings in less time. Secondly, it should be simple to use. Low-cost thermometers won’t last you long. Buying a low-cost thermometer may give you inaccurate readings most of the time. As they don’t have proper sensors. Consider reading the 4 best digital thermometer in UAE with Expert Reviews [2019]. This in-depth article will guide you in purchasing the right one. Remember to search for a product that offers all benefits as well emphasizes safety when making a purchase.

Tanisha Furtado
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