diff -uNr upower-0.99.5/src/linux/up-device-supply.c upower-0.99.5-patched/src/linux/up-device-supply.c
--- upower-0.99.5/src/linux/up-device-supply.c	2017-04-10 13:16:37.000000000 +0200
+++ upower-0.99.5-patched/src/linux/up-device-supply.c	2017-08-18 23:13:41.519668391 +0200
@@ -212,12 +212,17 @@
 	guint first = supply->priv->energy_old_first;
 	guint new_position = (first + UP_DEVICE_SUPPLY_ENERGY_OLD_LENGTH - 1) %
 		UP_DEVICE_SUPPLY_ENERGY_OLD_LENGTH;
+	GTimeVal now;
+	g_get_current_time (&now);
 
 	/* check if the energy value has changed and, if that's the case,
-	 * store the new values in the buffer. */
-	if (supply->priv->energy_old[first] != energy) {
+	 * store the new values in the buffer.
+	 * if the energy values has not changed and enough time has passed,
+	 * store the value anyway. */
+	if (supply->priv->energy_old[first] != energy ||
+		now.tv_sec - supply->priv->energy_old_timespec[first].tv_sec >= 300) {
 		supply->priv->energy_old[new_position] = energy;
-		g_get_current_time (&supply->priv->energy_old_timespec[new_position]);
+		supply->priv->energy_old_timespec[new_position] = now;
 		supply->priv->energy_old_first = new_position;
 		return TRUE;
 	}
@@ -256,7 +261,7 @@
 	now = supply->priv->energy_old_timespec[i];
 	do {
 		/* only use this value if it seems valid */
-		if (supply->priv->energy_old_timespec[i].tv_sec && supply->priv->energy_old[i]) {
+		if (supply->priv->energy_old_timespec[i].tv_sec) {
 			/* This is the square of t_i^2 */
 			sum_x += (now.tv_sec - supply->priv->energy_old_timespec[i].tv_sec) *
 				(now.tv_sec - supply->priv->energy_old_timespec[i].tv_sec);
@@ -272,16 +277,14 @@
 	} while (i != supply->priv->energy_old_first);
 
 	/* Check that at least 3 points were involved in computation */
-	if (sum_x == 0.0f || valid_values < 3)
+	if (valid_values < 3)
 		return supply->priv->rate_old;
 
 	/* Compute the discharge per hour, and not per second */
 	rate /= sum_x / SECONDS_PER_HOUR_F;
 
-	/* if the rate is zero, use the old rate. It will usually happens if no
-	 * data is in the buffer yet. If the rate is too high, i.e. more than,
-	 * 100W don't use it. */
-	if (rate == 0.0f || rate > 100.0f)
+	/* If the rate is too high, i.e. more than 100W don't use it. */
+	if (rate > 100.0f)
 		return supply->priv->rate_old;
 
 	return rate;