PROB-1869 Zen thermostat connecting with no battery state (SmartThingsCommunity#2671)

* PROB-1869 Zen thermostat connecting with no battery state
Changing algorithm for calculating battery % so it no longer need the check
for upper/lower limit of the received voltage.

* Update zen-thermostat.groovy

Author: marstorp

devicetypes/zenwithin/zen-thermostat.src/zen-thermostat.groovy

@@ -153,7 +153,7 @@ def updated() {
     // make sure supporedModes are in sync
     sendEvent(name: "supportedThermostatModes", value: supportedModes, eventType: "ENTITY_UPDATE", displayed: false)
     // Make sure we poll all attributes from the device
-    state.pollAdditionalData = state.pollAdditionalData - (24 * 60 * 60 * 1000)
+    state.pollAdditionalData = state.pollAdditionalData ? state.pollAdditionalData - (24 * 60 * 60 * 1000) : null
     // initialize() needs to be called after device details has been updated() but as installed() also calls this method and
     // that LiveLogging shows updated is being called more than one time, try avoiding multiple config/poll be done us runIn ;o(
     runIn(3, "initialize", [overwrite: true])
@@ -419,14 +419,14 @@ def updateBatteryStatus(rawValue) {
         // customAttribute in order to change UI icon/label
         def eventMap = [name: "batteryIcon", value: "err_battery", displayed: false]
         def linkText = getLinkText(device)
-        if (volts < 62 && volts != 0 && volts != 255) {
-            def minVolts = 34  // voltage when device UI starts to die
-            def maxVolts = 61  // 4 batteries at 1.5V should be 6.0V, however logs from users show 6,1 as well
-            def pct = (volts - minVolts) / (maxVolts - minVolts)
-            eventMap.value = Math.min(100, (int) pct * 100)
+        if (volts != 255) {
+            def minVolts = 34  // voltage when device UI starts to die, ie. when battery fails
+            def maxVolts = 60  // 4 batteries at 1.5V (6.0V)
+            def pct = (volts > minVolts) ? ((volts - minVolts) / (maxVolts - minVolts)) : 0
+            eventMap.value = Math.min(100, (int)(pct * 100))
             // Update capability "Battery"
             sendEvent(name: "battery", value: eventMap.value, descriptionText: "${getLinkText(device)} battery was ${eventMap.value}%")
-            eventMap.value = eventMap.value > 10 ? eventMap.value : "low_battery"
+            eventMap.value = eventMap.value > 15 ? eventMap.value : "low_battery"
         }
         sendEvent(eventMap)
     } else {