• The RDE300 series software determines soiling ratio by analyzing readings within a specific time window each day and calculating a soiling ratio at the end of the soiling analysis time window. 
  • RDE300 units use an internal clock to determine which readings are within the analysis time window and when the window ends. 
  • A small battery allows the clock to maintain time when the RDE300 unit is not powered.


  • Eventually the clock battery may fail, either due to age or temperature stress. 
  • Symptoms of this problem include:
    • The unit will not maintain the correct time after power is cycled
    • The unit will not calculate soiling ratios because clock time is not correct


1. Send the Unit to Atonometrics to Replace the Clock Battery

Atonometrics can replace the clock battery on your RDE300 PCB. Please submit a support ticket to receive an RMA number for this service.

2. Customer Replacement of the Clock Battery

If sending the unit to Atonometrics is not feasible, you may replace the clock battery on your unit.


  • Replacing the clock battery requires accessing the circuit board. Hazardous voltages may be present. This procedure should be performed by qualified personnel only.

Required Tools & Materials:

  • Screwdriver (for removing the circuit board)
  • Small wire cutters
  • Soldering Iron
  • Solder
  • Replacement battery
    • Panasonic BR-1225A/FAN
    • Available at Digikey (link) and other suppliers


  • Remove the RDE300 Series PCB from its enclosure, following the relevant instructions in Replacing the PCB on an RDE300 unit
  • Take caution with the PCB to avoid damaging it.
    • Be careful not to damage any small components when handling the PCB or placing it on a work surface
    • Take precautions to avoid electrostatic discharge which could damage components
  • Locate the battery, component reference designator BT1, using the photos below
  • Using a soldering iron, carefully remove the battery without damaging the PCB. It may be helpful to cut one or both of the battery leads during removal.
  • Using the soldering iron, carefully install the replacement battery in the BT1 position on the board. Ensure polarity matches the photos.
  • Replace the PCB in the enclosure, following relevant instructions in Replacing the PCB on an RDE300 unit 
  • Use the RDE300 Series Engineering Client Software to set the time on the RDE300 clock
  • Turn off power for a minute and turn power back on.
  • Use the software again to verify that the clock time was maintained while power was off.


3. Workaround: Change Soiling Analysis Settings

If your unit normally remains continuously powered, a simple workaround -- without replacing the battery -- is to update the Soiling Analysis settings (see RDE300 Series User Guide) as follows:

Min Irradiance (W/m2)500
Time Window (Hours +/- 12 Noon)11

With these settings, the unit will attempt to process data during 22 hours a day but only when irradiance exceeds 500 W/m2, corresponding to the middle part of the day.

Note however that this solution will not work if your unit is powered down regularly. For example, if the unit is typically powered off at night, then with this solution it is possible that no result would ever be produced since the unit may be off at the end of the analysis time window. In these cases, you should replace the battery using one of the options listed above.