diff --git a/widgets/bat.lua b/widgets/bat.lua
index 615f9dd..2f93518 100644
--- a/widgets/bat.lua
+++ b/widgets/bat.lua
@@ -73,8 +73,9 @@ local function worker(format, warg)
         else
             return {state, percent, time}
         end
-        local hoursleft = math.floor(timeleft)
-        local minutesleft = math.floor((timeleft - hoursleft) * 60 )
+        -- Calculate time (but work around broken BAT/ACPI implementations)
+        local hoursleft = math.min(math.floor(timeleft), 0)
+        local minutesleft = math.min(math.floor((timeleft - hoursleft) * 60 ), 0)
         time = string.format("%02d:%02d", hoursleft, minutesleft)
     end