Refresh battery list on change checked every 2s (configurable)

default_config.lua

@@ -171,7 +171,8 @@ config.widgets = {
         battery = {
             enabled = true,
             screens = { 1, 2 },
-            refresh_interval = 30, -- In seconds
+            refresh_interval = 15, -- In seconds
+            list_refresh_interval = 2, -- In seconds
             precision = 0, -- How many decimals
         },
     },

simple/widgets/system_resources.lua

@@ -135,14 +135,9 @@ gears.timer {
 ---
 --- Batteries
 ---
-local rawBatteries = readCommand("ls -A1 /sys/class/power_supply")
-
-function getBatteries()
-    return rawBatteries:gmatch("([^\n]+)")
-end
-
-function hasBattery()
-    return rawBatteries:len() > 0
+rawBatteries = {}
+function refreshRawBatteries()
+	rawBatteries = readCommand("ls -A1 /sys/class/power_supply")
 end
 
 function getBatteryLevel(battery)
@@ -170,8 +165,25 @@ end
 local batteryContainer = wibox.widget {
     layout = wibox.layout.flex.horizontal
 }
-if hasBattery() then
-    for battery in getBatteries() do
+local timers = {}
+function refreshBatteries()
+	-- refresh raw batteries and check for change
+	local oldBatteries = rawBatteries
+	refreshRawBatteries()
+	if rawBatteries == oldBatteries then
+		return
+	end
+
+	-- clear timers
+	for i,v in ipairs(timers) do
+		v:stop()
+	end
+	timers = {};
+
+	-- clear layout
+	batteryContainer:set_children({})
+
+	for battery in rawBatteries:gmatch("([^\n]+)") do
 		local path = "/sys/class/power_supply/" .. battery
 		if readCommand("cat " .. path .. "/type"):match("Battery") then
 			-- widget
@@ -195,7 +207,7 @@ if hasBattery() then
 
 			-- update battery level
 			local batteryText = widget:get_children()[1]
-            gears.timer {
+			local timer = gears.timer {
 				timeout = config.battery.refresh_interval,
 				call_now = true,
 				autostart = true,
@@ -203,15 +215,21 @@ if hasBattery() then
 					batteryText.markup = (isCharging(path) and "+" or "") .. getBatteryLevel(path)
 				end
 			}
+			table.insert(timers, timer)
 
 			batteryContainer:add(widget)
 		end
 	end
-else
-    batteryContainer = nil
 end
 
-
+gears.timer {
+    timeout = config.battery.list_refresh_interval,
+    call_now = true,
+    autostart = true,
+    callback = function()
+        refreshBatteries()
+    end
+}
 
 return {
     bars = bars,