145.5 Temperatures outside operating range5.6 Low battery detectionTemperatures below 10 °C are displayed without the leading ‘0’. Temperatures exceeding the measurable range will be indicated by ‘HI’ for temperaturesabove the upper limit, and ‘LO’ for temperatures below the lower limit, as shown in the images.Battery voltage is checked every minute. When the battery voltage drops to a certain level, the Low-Battery warning indicator appears.• The thermostat functions normally during low battery. However, user must change the batteries as soon as possible before the battery is too weakfor the normal operation to be assured.• When you change the batteries, you have about 30 seconds to to do so without losing your settings.