diff --git a/includes/discovery/functions.inc.php b/includes/discovery/functions.inc.php
index 2e55a09e87..0e891a031e 100644
--- a/includes/discovery/functions.inc.php
+++ b/includes/discovery/functions.inc.php
@@ -216,6 +216,10 @@ function discover_volt($device, $oid, $index, $type, $descr, $precision = 1, $lo
   
   if (mysql_result(mysql_query("SELECT count(volt_id) FROM `voltage` WHERE device_id = '".$device['device_id']."' AND volt_type = '$type' AND `volt_index` = '$index'"),0) == '0')
   {
+
+    if(!$high_limit && isset($current)) { $high_limit = round($current * 1.05, 2); }
+    if(!$low_limit && isset($current))  { $low_limit = round($current * 0.95, 2); }
+
     $query = "INSERT INTO voltage (`device_id`, `volt_oid`, `volt_index`, `volt_type`, `volt_descr`, `volt_precision`, `volt_limit`, `volt_limit_low`, `volt_current`) ";
     $query .= " VALUES ('".$device['device_id']."', '$oid', '$index', '$type', '$descr', '$precision', '$high_limit', '$low_limit', '$current')";
     mysql_query($query);
@@ -224,16 +228,25 @@ function discover_volt($device, $oid, $index, $type, $descr, $precision = 1, $lo
   }
   else
   {
+
     $volt_entry = mysql_fetch_array(mysql_query("SELECT * FROM `voltage` WHERE device_id = '".$device['device_id']."' AND volt_type = '$type' AND `volt_index` = '$index'"));
-    if($oid == $volt_entry['volt_oid'] && $descr == $volt_entry['volt_descr'] && $precision == $volt_entry['volt_precision'])
+
+    if(!isset($current) && isset($volt_entry['current'])) { $current = $volt_entry['current']; }
+
+
+    if(!$high_limit && !$volt_entry['volt_limit'] && $current)  { $high_limit = round($current * 1.05, 2); } elseif (!$high_limit && $volt_entry['volt_limit']) { $high_limit = $volt_entry['volt_limit']; }
+    if(!$low_limit && !$volt_entry['volt_limit_low'] && $current)   { $low_limit = round($current * 0.95, 2); } elseif (!$low_limit && $volt_entry['volt_limit_low']) { $low_limit = $volt_entry['volt_limit_low']; }
+
+    if($oid == $volt_entry['volt_oid'] && $descr == $volt_entry['volt_descr'] && $precision == $volt_entry['volt_precision'] && $volt_entry['volt_limit'] == $high_limit && $volt_entry['volt_limit_low'] == $low_limit)
     {
       echo(".");
     }
     else
     {
-      mysql_query("UPDATE voltage SET `volt_descr` = '$descr', `volt_oid` = '$oid', `volt_precision` = '$precision' WHERE `device_id` = '" . $device['device_id'] . "' AND volt_type = '$type' AND `volt_index` = '$index' ");
+      $sql = "UPDATE voltage SET `volt_descr` = '$descr', `volt_oid` = '$oid', `volt_precision` = '$precision', `volt_limit_low` = '$low_limit', `volt_limit` = '$high_limit' WHERE `device_id` = '" . $device['device_id'] . "' AND volt_type = '$type' AND `volt_index` = '$index'";
+      $query = mysql_query($sql);
       echo("U");
-      if($debug) { echo("$query ". mysql_affected_rows() . " updated"); }
+      if($debug) { echo("$sql ". mysql_affected_rows() . " updated"); }
     }
   }