diff --git a/ion/src/device/battery.cpp b/ion/src/device/battery.cpp
index 1a84f7242..7a90de928 100644
--- a/ion/src/device/battery.cpp
+++ b/ion/src/device/battery.cpp
@@ -2,6 +2,14 @@
 #include "battery.h"
 #include "regs/regs.h"
 
+/* To measure the battery voltage, we're using the internal ADC. The ADC works
+ * by comparing the input voltage to a reference voltage. The only fixed voltage
+ * we have around is 2.8V, so that's the one we're using as a refrence. However,
+ * and ADC can only measure voltage that is lower than the reference voltage. So
+ * we need to use a voltage divider before sampling Vbat.
+ * To avoid draining the battery, we're using an high-impedence voltage divider,
+ * so we need to be careful when sampling the ADC. See AN2834 for more info. */
+
 namespace Ion {
 namespace Battery {
 
@@ -19,7 +27,6 @@ float voltage() {
   return Device::ADCDividerBridgeRatio*(Device::ADCReferenceVoltage * value)/0xFFF;
 }
 
-
 }
 }
 
@@ -43,6 +50,10 @@ void initGPIO() {
   /* The BAT_SNS pin is connected to Vbat through a divider bridge. It therefore
    * has a voltage of Vbat/2. We'll measure this using ADC channel 0. */
   ADCGPIO.MODER()->setMode(ADCPin, GPIO::MODER::Mode::Analog);
+
+  ADC.SMPR()->setSamplingTime(ADCChannel, ADC::SMPR::SamplingTime::Cycles480);
+  // ADC.SQR1()->setL(0); // Default
+  ADC.SQR3()->setSQ1(ADCChannel);
 }
 
 void initADC() {
diff --git a/ion/src/device/battery.h b/ion/src/device/battery.h
index d057583ed..cc4e0fa77 100644
--- a/ion/src/device/battery.h
+++ b/ion/src/device/battery.h
@@ -9,19 +9,20 @@ namespace Device {
 
 /*  Pin | Role              | Mode                  | Function
  * -----+-------------------+-----------------------+----------
- *  PA0 | BAT_SNS           | Analog                | ADC1_0
- *  PC2 | BAT_CHRG          | Input, pulled up      |
+ *  PA0 | BAT_CHRG          | Input, pulled up      | Low = charging, high = full
+ *  PA1 | VBAT_SNS          | Analog                | ADC1_1
  */
 
 void init();
 void initGPIO();
 void initADC();
 
-constexpr GPIO ChargingGPIO = GPIOC;
-constexpr uint8_t ChargingPin = 2;
+constexpr GPIO ChargingGPIO = GPIOA;
+constexpr uint8_t ChargingPin = 0;
 
 constexpr GPIO ADCGPIO = GPIOA;
-constexpr uint8_t ADCPin = 0;
+constexpr uint8_t ADCPin = 1;
+constexpr uint8_t ADCChannel = 1;
 
 constexpr float ADCReferenceVoltage = 2.8f;
 constexpr float ADCDividerBridgeRatio = 2.0f;
diff --git a/ion/src/device/regs/adc.h b/ion/src/device/regs/adc.h
index 1c79145d4..2881cf23b 100644
--- a/ion/src/device/regs/adc.h
+++ b/ion/src/device/regs/adc.h
@@ -19,7 +19,7 @@ public:
     REGS_BOOL_FIELD(ADON, 0);
     REGS_BOOL_FIELD(SWSTART, 30);
   };
-#if 0
+
   class SMPR : Register64 {
     /* The SMPR register doesn't exist per-se in the documentation. It is the
      * consolidation of SMPR1 and SMPR2 which are two 32-bit registers. */
@@ -34,14 +34,23 @@ public:
       Cycles144 = 6,
       Cycles480 = 7
     };
-    SamplingTime setSamplingTime(int channel) {
-      return (SamplingTime)getBitRange(3*index+2, 3*index);
+    SamplingTime getSamplingTime(int channel) {
+      return (SamplingTime)getBitRange(3*channel+2, 3*channel);
     }
     void setSamplingTime(int channel, SamplingTime t) volatile {
-      setBitRange(3*index+2, 3*index, (uint64_t)t);
+      setBitRange(3*channel+2, 3*channel, (uint64_t)t);
     }
   };
-#endif
+
+  class SQR1 : Register32 {
+  public:
+    REGS_FIELD(L, uint8_t, 23, 20);
+  };
+
+  class SQR3 : Register32 {
+  public:
+    REGS_FIELD(SQ1, uint8_t, 4, 0);
+  };
 
   class DR : public Register16 {
   };
@@ -49,6 +58,9 @@ public:
   constexpr ADC() {};
   REGS_REGISTER_AT(SR, 0x0);
   REGS_REGISTER_AT(CR2, 0x08);
+  REGS_REGISTER_AT(SMPR, 0x0C);
+  REGS_REGISTER_AT(SQR1, 0x2C);
+  REGS_REGISTER_AT(SQR3, 0x34);
   REGS_REGISTER_AT(DR, 0x4C);
 private:
   constexpr uint32_t Base() const {