Heat Meter Battery: Lifetime, Replacement and What Happens When It Runs Out

How Long Does a Heat Meter Battery Last?

Battery life varies by brand, model, battery capacity and operating conditions. The values below are taken from the manufacturers' data sheets and manuals:

Since there may be different generations and battery options within the same brand, check your meter's model and year of manufacture on its label. Two conditions stated by the manufacturers directly affect battery life:

• Ambient temperature: The Calmet PM02 document states that the same battery lasts 6 or 10 years below 30 °C, and 5 or 9 years below 45 °C. Danfoss recommends installing the calculator unit in an environment of at most 45 °C for battery life.
• Communication frequency: In wireless modules, the shorter the transmission interval, the faster the battery is depleted. The 16+1-year life stated for the own battery of Danfoss's wireless communication module drops to 10+1 years with a transmission every 2 minutes; ZENNER also sets the transmission interval according to the battery equipment.

What Happens When the Battery Runs Out? Is the Reading Lost?

Meters give a warning before the battery runs out. What the warning looks like depends on the brand:

• Minol Zenner C5: The EOb display on level 3 shows the year the battery life ends; error 7 indicates that the battery voltage has dropped, and error 1000 indicates that the battery life has ended.
• Danfoss SonoSafe 10 / SonoSelect 10: E05 indicates less than 12 months of battery life left, E03 less than 1 month; E04 indicates low battery voltage. There is also a battery symbol on the display.
• Honeywell EW700: An empty battery symbol appears on the display.
• Calmet PM02: There is a battery warning symbol on the display.
• Qundis Q caloric 5.5: When the battery life has expired, the text bAt00 appears, depending on the programming.

When the battery is completely depleted, a calculator unit that runs only on battery cannot measure; consumption during this period is not recorded. That is why you need to act as soon as you see the warning.

Most manufacturers do not state clearly in their user documents whether the accumulated reading is preserved. An example that does is the Calmet PM02: every day at midnight the meter writes the total heating and cooling energy, volume and operating time to non-volatile flash memory. Whatever the brand, the safest way is to have the reading photographed before and after the battery replacement and entered in the service record.

Can the User Replace the Heat Meter Battery?

No. The battery is inside the calculator unit; manufacturers leave battery replacement to authorized service providers and ask that the seals are not touched:

• Honeywell: The instructions ask you to contact an authorized service provider for battery replacement and treat removal of the seals as tampering.
• Calmet: According to the technical document, only the manufacturer's service center may replace the PM02 battery; a meter with broken seals cannot be used as a basis for billing.
• Danfoss: Battery replacement is done by breaking the installation seal; when the cover is opened, the meter gives an E13 tamper alarm, which can only be reset with a service tool.
• Minol Zenner: ZENNER states that repairs may only be carried out by the manufacturer or an authorized service provider, and that the possibility of battery replacement differs from country to country.
• Qundis: The manufacturer states that the battery in its heat cost allocators cannot be replaced; the whole device must be replaced.

The seal is not only a warranty matter. Under Türkiye's Heat Meter Inspection Regulation, for example, a meter without a stamp, or whose stamp or body has evidently been tampered with, is not re-verified; similar rules apply in many countries. A meter you have opened yourself cannot be re-verified, even if it measures correctly.

Battery and Periodic Re-verification

Re-verification periods depend on national rules; check your local regulations for periodic re-verification requirements. In Türkiye, for example, the periodic re-verification period for heat meters is 5 years; the year in which the meter was stamped counts as the first year, and the application is made in January–February of the year following the year in which the period expires. In a meter with a battery life of at least 7 years, the battery will complete the first re-verification period but may run out before the second period (year 10) ends. It is therefore practical to assess the battery condition when the meter goes for re-verification. Battery replacement does not replace re-verification; re-verification and stamping are a separate procedure. For our re-verification process, see our Heat Meter Re-verification and Calibration page.

Battery Replacement or Meter Replacement?

• Battery replacement: If the model's battery can be replaced and the meter's re-verification period also allows it, the battery is replaced at an authorized service provider with an original battery suitable for the model.
• Meter replacement: For devices whose battery cannot be replaced, old meters that are also due for re-verification or meters showing error codes, installing a new meter is often the more sensible choice. When replacing, choosing a model with the same size, body length and connection thread makes installation easier.

For models, see our Heat Meters and ultrasonic heat meter categories; for installation parts, our heat meter spare parts category; for radiator-based measurement, our heat cost allocator category. Brand pages: Minol Zenner, Danfoss, Honeywell, CEM, Calmet, İntegral, Novus Digitermo, Qundis.

What to Do When You See a Battery Warning

• Take a photo of the display and the error code, and note the reading on the main display together with its unit.
• Report the situation to your building management or meter reading company.
• Do not open the cover, do not touch the seals or cables, and do not try to fit a battery yourself.
• If another code appears together with the battery warning, you can look up its meaning in our Heat Meter Error Codes guide. Our guide How to Read a Heat Meter explains how to read the values on the display.