diff --git a/thermidity-avr/bitmaps.c b/thermidity-avr/bitmaps.c
index 28b015d..bddbee1 100644
--- a/thermidity-avr/bitmaps.c
+++ b/thermidity-avr/bitmaps.c
@@ -11,65 +11,113 @@
 #include "utils.h"
 
 const uint8_t BAT_0PCT_DATA[] PROGMEM = {
-    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 
     0x3f, 0xff, 0xff, 0xf0, 0x3f, 0xff, 0xff, 0xf0,
-    0x30, 0x00, 0x00, 0x30, 0x30, 0x00, 0x00, 0x30,
+    0x30, 0x00, 0x00, 0x30, 0x30, 0x00, 0x00, 0x30, 
     0x30, 0x00, 0x00, 0x3c, 0x30, 0x00, 0x00, 0x3c,
-    0x30, 0x00, 0x00, 0x3c, 0x30, 0x00, 0x00, 0x3c,
+    0x30, 0x00, 0x00, 0x3c, 0x30, 0x00, 0x00, 0x3c, 
     0x30, 0x00, 0x00, 0x30, 0x30, 0x00, 0x00, 0x30,
+    0x3f, 0xff, 0xff, 0xf0, 0x3f, 0xff, 0xff, 0xf0, 
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
+};
+
+const uint8_t BAT_13PCT_DATA[] PROGMEM = {
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 
     0x3f, 0xff, 0xff, 0xf0, 0x3f, 0xff, 0xff, 0xf0,
+    0x3c, 0x00, 0x00, 0x30, 0x3c, 0x00, 0x00, 0x30, 
+    0x3c, 0x00, 0x00, 0x3c, 0x3c, 0x00, 0x00, 0x3c,
+    0x3c, 0x00, 0x00, 0x3c, 0x3c, 0x00, 0x00, 0x3c, 
+    0x3c, 0x00, 0x00, 0x30, 0x3c, 0x00, 0x00, 0x30,
+    0x3f, 0xff, 0xff, 0xf0, 0x3f, 0xff, 0xff, 0xf0, 
     0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
 };
 
 const uint8_t BAT_25PCT_DATA[] PROGMEM = {
-    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 
     0x3f, 0xff, 0xff, 0xf0, 0x3f, 0xff, 0xff, 0xf0,
-    0x3f, 0xc0, 0x00, 0x30, 0x3f, 0xc0, 0x00, 0x30,
-    0x3f, 0xc0, 0x00, 0x3c, 0x3f, 0xc0, 0x00, 0x3c,
-    0x3f, 0xc0, 0x00, 0x3c, 0x3f, 0xc0, 0x00, 0x3c,
-    0x3f, 0xc0, 0x00, 0x30, 0x3f, 0xc0, 0x00, 0x30,
+    0x3f, 0x80, 0x00, 0x30, 0x3f, 0x80, 0x00, 0x30, 
+    0x3f, 0x80, 0x00, 0x3c, 0x3f, 0x80, 0x00, 0x3c,
+    0x3f, 0x80, 0x00, 0x3c, 0x3f, 0x80, 0x00, 0x3c, 
+    0x3f, 0x80, 0x00, 0x30, 0x3f, 0x80, 0x00, 0x30,
+    0x3f, 0xff, 0xff, 0xf0, 0x3f, 0xff, 0xff, 0xf0, 
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
+};
+
+const uint8_t BAT_38PCT_DATA[] PROGMEM = {
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 
     0x3f, 0xff, 0xff, 0xf0, 0x3f, 0xff, 0xff, 0xf0,
+    0x3f, 0xf0, 0x00, 0x30, 0x3f, 0xf0, 0x00, 0x30, 
+    0x3f, 0xf0, 0x00, 0x3c, 0x3f, 0xf0, 0x00, 0x3c,
+    0x3f, 0xf0, 0x00, 0x3c, 0x3f, 0xf0, 0x00, 0x3c, 
+    0x3f, 0xf0, 0x00, 0x30, 0x3f, 0xf0, 0x00, 0x30,
+    0x3f, 0xff, 0xff, 0xf0, 0x3f, 0xff, 0xff, 0xf0, 
     0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
 };
 
 const uint8_t BAT_50PCT_DATA[] PROGMEM = {
-    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 
     0x3f, 0xff, 0xff, 0xf0, 0x3f, 0xff, 0xff, 0xf0,
-    0x3f, 0xff, 0x00, 0x30, 0x3f, 0xff, 0x00, 0x30,
-    0x3f, 0xff, 0x00, 0x3c, 0x3f, 0xff, 0x00, 0x3c,
-    0x3f, 0xff, 0x00, 0x3c, 0x3f, 0xff, 0x00, 0x3c,
-    0x3f, 0xff, 0x00, 0x30, 0x3f, 0xff, 0x00, 0x30,
+    0x3f, 0xfe, 0x00, 0x30, 0x3f, 0xfe, 0x00, 0x30, 
+    0x3f, 0xfe, 0x00, 0x3c, 0x3f, 0xfe, 0x00, 0x3c,
+    0x3f, 0xfe, 0x00, 0x3c, 0x3f, 0xfe, 0x00, 0x3c, 
+    0x3f, 0xfe, 0x00, 0x30, 0x3f, 0xfe, 0x00, 0x30,
+    0x3f, 0xff, 0xff, 0xf0, 0x3f, 0xff, 0xff, 0xf0, 
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
+};
+
+const uint8_t BAT_63PCT_DATA[] PROGMEM = {
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 
     0x3f, 0xff, 0xff, 0xf0, 0x3f, 0xff, 0xff, 0xf0,
+    0x3f, 0xff, 0xc0, 0x30, 0x3f, 0xff, 0xc0, 0x30, 
+    0x3f, 0xff, 0xc0, 0x3c, 0x3f, 0xff, 0xc0, 0x3c,
+    0x3f, 0xff, 0xc0, 0x3c, 0x3f, 0xff, 0xc0, 0x3c, 
+    0x3f, 0xff, 0xc0, 0x30, 0x3f, 0xff, 0xc0, 0x30,
+    0x3f, 0xff, 0xff, 0xf0, 0x3f, 0xff, 0xff, 0xf0, 
     0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
 };
 
 const uint8_t BAT_75PCT_DATA[] PROGMEM = {
-    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 
     0x3f, 0xff, 0xff, 0xf0, 0x3f, 0xff, 0xff, 0xf0,
-    0x3f, 0xff, 0xf8, 0x30, 0x3f, 0xff, 0xf8, 0x30,
+    0x3f, 0xff, 0xf8, 0x30, 0x3f, 0xff, 0xf8, 0x30, 
     0x3f, 0xff, 0xf8, 0x3c, 0x3f, 0xff, 0xf8, 0x3c,
-    0x3f, 0xff, 0xf8, 0x3c, 0x3f, 0xff, 0xf8, 0x3c,
+    0x3f, 0xff, 0xf8, 0x3c, 0x3f, 0xff, 0xf8, 0x3c, 
     0x3f, 0xff, 0xf8, 0x30, 0x3f, 0xff, 0xf8, 0x30,
+    0x3f, 0xff, 0xff, 0xf0, 0x3f, 0xff, 0xff, 0xf0, 
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
+};
+
+const uint8_t BAT_88PCT_DATA[] PROGMEM = {
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 
     0x3f, 0xff, 0xff, 0xf0, 0x3f, 0xff, 0xff, 0xf0,
+    0x3f, 0xff, 0xff, 0x30, 0x3f, 0xff, 0xff, 0x30, 
+    0x3f, 0xff, 0xff, 0x3c, 0x3f, 0xff, 0xff, 0x3c,
+    0x3f, 0xff, 0xff, 0x3c, 0x3f, 0xff, 0xff, 0x3c, 
+    0x3f, 0xff, 0xff, 0x30, 0x3f, 0xff, 0xff, 0x30,
+    0x3f, 0xff, 0xff, 0xf0, 0x3f, 0xff, 0xff, 0xf0, 
     0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
 };
 
 const uint8_t BAT_100PCT_DATA[] PROGMEM = {
-    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 
     0x3f, 0xff, 0xff, 0xf0, 0x3f, 0xff, 0xff, 0xf0,
-    0x3f, 0xff, 0xff, 0xf0, 0x3f, 0xff, 0xff, 0xf0,
+    0x3f, 0xff, 0xff, 0xf0, 0x3f, 0xff, 0xff, 0xf0, 
     0x3f, 0xff, 0xff, 0xfc, 0x3f, 0xff, 0xff, 0xfc,
-    0x3f, 0xff, 0xff, 0xfc, 0x3f, 0xff, 0xff, 0xfc,
+    0x3f, 0xff, 0xff, 0xfc, 0x3f, 0xff, 0xff, 0xfc, 
     0x3f, 0xff, 0xff, 0xf0, 0x3f, 0xff, 0xff, 0xf0,
-    0x3f, 0xff, 0xff, 0xf0, 0x3f, 0xff, 0xff, 0xf0,
+    0x3f, 0xff, 0xff, 0xf0, 0x3f, 0xff, 0xff, 0xf0, 
     0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
 };
 
 const Bitmap bitmaps[] PROGMEM = {
     {32, 16, BAT_0PCT_DATA},
+    {32, 16, BAT_13PCT_DATA},
     {32, 16, BAT_25PCT_DATA},
+    {32, 16, BAT_38PCT_DATA},
     {32, 16, BAT_50PCT_DATA},
+    {32, 16, BAT_63PCT_DATA},
     {32, 16, BAT_75PCT_DATA},
+    {32, 16, BAT_88PCT_DATA},
     {32, 16, BAT_100PCT_DATA}
 };
 
diff --git a/thermidity-avr/bitmaps.h b/thermidity-avr/bitmaps.h
index 34dfb4c..951b8d4 100644
--- a/thermidity-avr/bitmaps.h
+++ b/thermidity-avr/bitmaps.h
@@ -11,10 +11,14 @@
 #include <stdint.h>
 
 #define BAT_0PCT    0
-#define BAT_25PCT   1
-#define BAT_50PCT   2
-#define BAT_75PCT   3
-#define BAT_100PCT  4
+#define BAT_13PCT   1
+#define BAT_25PCT   2
+#define BAT_38PCT   3
+#define BAT_50PCT   4
+#define BAT_63PCT   5
+#define BAT_75PCT   6
+#define BAT_88PCT   7
+#define BAT_100PCT  8
 
 /**
  * A bitmap with its width and height, and data.
diff --git a/thermidity-avr/meter.c b/thermidity-avr/meter.c
index f394304..a04f58e 100644
--- a/thermidity-avr/meter.c
+++ b/thermidity-avr/meter.c
@@ -7,6 +7,7 @@
 
 #include <stdio.h>
 #include <stdlib.h>
+#include <stdbool.h>
 #include <math.h>
 #include <avr/sleep.h>
 #include <util/delay.h>
@@ -18,7 +19,6 @@
 #include "dejavu.h"
 #include "bitmaps.h"
 #include "display.h"
-#include "usart.h"
 #include "utils.h"
 
 static uint32_t avgADCTmp = -1;
@@ -98,11 +98,15 @@
  * @param vBatx10
  * @return index
  */
-static uint8_t bitmapBat(int8_t vBatx10) {
-    if (vBatx10 < 32) return BAT_0PCT;
-    if (vBatx10 < 36) return BAT_25PCT;
-    if (vBatx10 < 40) return BAT_50PCT;
-    if (vBatx10 < 44) return BAT_75PCT;
+static uint8_t bitmapBat(int8_t vBatx10) {    
+    if (vBatx10 < 31) return BAT_0PCT;
+    if (vBatx10 < 33) return BAT_13PCT;
+    if (vBatx10 < 35) return BAT_25PCT;
+    if (vBatx10 < 37) return BAT_38PCT;
+    if (vBatx10 < 39) return BAT_50PCT;
+    if (vBatx10 < 41) return BAT_63PCT;
+    if (vBatx10 < 43) return BAT_75PCT;
+    if (vBatx10 < 45) return BAT_88PCT;
     return BAT_100PCT;
 }
 
@@ -119,6 +123,10 @@
     return buf;
 }
 
+int16_t getMVBat(void) {
+    return (avgMVBat >> EWMA_BS);
+}
+
 void measureValues(void) {
     avgADCTmp = convert(AREF_AVCC, PIN_TMP, true, avgADCTmp);
     avgADCRh = convert(AREF_AVCC, PIN_RH, true, avgADCRh);
@@ -162,10 +170,10 @@
     writeBitmap(0, 216, bitmapBat(vBatx10));
     // temperature with label
     writeString(1, 0, dejavu, formatTmp(tmpx10));
-    writeString(5, 152, unifont, "Temperature");
+    writeString(5, 144, unifont, "Temperature");
     // humidity with label
     writeString(8, 0, dejavu, formatRh(rh));
-    writeString(12, 152, unifont, "Humidity");
+    writeString(12, 144, unifont, "Humidity");
     // update display
     doDisplay();
-}
\ No newline at end of file
+}
diff --git a/thermidity-avr/meter.h b/thermidity-avr/meter.h
index eddaae4..1baa718 100644
--- a/thermidity-avr/meter.h
+++ b/thermidity-avr/meter.h
@@ -30,9 +30,15 @@
 #define RH_ADC_100  3225 // Vout = Vsupply * 0.7875
 #define RH_ADC      RH_ADC_100 - RH_ADC_0
 
+/** Battery cutoff voltage in millivolts */
+#define BAT_LOW     3000
+
 /** Weight of the exponential weighted moving average as bit shift */
 #define EWMA_BS     4
 
+/** Returns the battery voltage in millivolts divided by 5 */
+int16_t getMVBat(void);
+
 /**
  * Measures temperature, relative humidity and battery voltage and updates 
  * the average values.
diff --git a/thermidity-avr/pins.h b/thermidity-avr/pins.h
index 8964f23..56eefa2 100644
--- a/thermidity-avr/pins.h
+++ b/thermidity-avr/pins.h
@@ -10,7 +10,7 @@
 
 #include <avr/io.h>
 
-/* Vref and Sensors */
+/* Sensors */
 #define DDR_SENS  DDRC
 #define PORT_SENS PORTC
 #define PIN_PWR   PC1
diff --git a/thermidity-avr/thermidity.c b/thermidity-avr/thermidity.c
index 2459215..e283002 100644
--- a/thermidity-avr/thermidity.c
+++ b/thermidity-avr/thermidity.c
@@ -33,7 +33,7 @@
 #include "utils.h"
 #include "usart.h"
 
-/* Measure and average temperature and relative humidity every 32 seconds */
+/* Measure and average temperature and relative humidity every ~32 seconds */
 #define MEASURE_SECS    32
 /* Display should not be updated more frequently than once every 180 seconds */
 #define DISP_UPD_SECS   288
@@ -54,7 +54,7 @@
     DDR_SENS |= (1 << PIN_PWR);
     // drive sensor power pin low
     PORT_SENS &= ~(1 << PIN_PWR);
-    
+
     // set MOSI and SCK as output pin
     DDR_SPI |= (1 << PIN_MOSI);
     DDR_SPI |= (1 << PIN_SCK);
@@ -78,7 +78,7 @@
 
     // set display BUSY pin as input pin (default)
     DDR_DISP &= ~(1 << PIN_BUSY);
-    
+
     // pull all unused pins high/set to defined level to reduce current
     // consumption when not in sleep mode
     PORTB |= (1 << PB6);
@@ -161,6 +161,16 @@
     PRR |= (1 << PRTWI) | (1 << PRTIM0) | (1 << PRTIM1) | (1 << PRTIM2) | (1 << PRUSART0);
 }
 
+/**
+ * Disables global interrupts and the watchdog to stop measuring 
+ * and updating the display when batteries are too weak, to limit 
+ * discharging below cutoff voltage.
+ */
+static void powerDown(void) {
+    cli();
+    wdt_disable();
+}
+
 int main(void) {
 
     reducePower();
@@ -178,7 +188,7 @@
         ATOMIC_BLOCK(ATOMIC_FORCEON) {
             secsCopy = secs;
         }
-        
+
         if (secsCopy % MEASURE_SECS == 0) {
             powerOnSensors();
             // give the humidity sensor time to settle
@@ -192,11 +202,16 @@
                 ATOMIC_BLOCK(ATOMIC_FORCEON) {
                     secs = 0;
                 }
-                
-                displayValues();
+
+                // measured battery voltage is /5 by voltage divider
+                if (getMVBat() < BAT_LOW / 5) {
+                    powerDown();
+                } else {
+                    displayValues();
+                }
             }
         }
-                
+
         set_sleep_mode(SLEEP_MODE_PWR_DOWN);
         sleep_mode();
     }