diff --git a/app/src/main/java/eu/darken/capod/monitor/core/BatteryReading.kt b/app/src/main/java/eu/darken/capod/monitor/core/BatteryReading.kt
new file mode 100644
index 00000000..c2339b89
--- /dev/null
+++ b/app/src/main/java/eu/darken/capod/monitor/core/BatteryReading.kt
@@ -0,0 +1,29 @@
+package eu.darken.capod.monitor.core
+
+import eu.darken.capod.pods.core.apple.ble.BATTERY_RESOLUTION_DECILE
+import eu.darken.capod.pods.core.apple.ble.BATTERY_RESOLUTION_PERCENT
+import eu.darken.capod.pods.core.apple.ble.devices.HasCase
+
+/**
+ * A battery percentage together with the step size of the source it came from. A reading of 20%
+ * from a decile source means "somewhere in [20%, 30%)", which is the difference between a claim we
+ * can make and one we can't.
+ */
+data class BatteryReading(
+    val percent: Float,
+    val resolution: Float,
+)
+
+/**
+ * [PodDevice.batteryCase] resolved through the same precedence, but keeping the resolution of
+ * whichever source won. Cache entries store no resolution, so they report the coarsest one.
+ */
+val PodDevice.batteryCaseReading: BatteryReading?
+    get() {
+        aap?.batteryCase?.let { return BatteryReading(it, BATTERY_RESOLUTION_PERCENT) }
+        (ble as? HasCase)?.let { snapshot ->
+            snapshot.batteryCasePercent?.let { return BatteryReading(it, snapshot.batteryCaseResolution) }
+        }
+        cached?.case?.percent?.let { return BatteryReading(it, BATTERY_RESOLUTION_DECILE) }
+        return null
+    }
diff --git a/app/src/main/java/eu/darken/capod/pods/core/apple/ble/PodDeviceExtensions.kt b/app/src/main/java/eu/darken/capod/pods/core/apple/ble/PodDeviceExtensions.kt
index 3c45ef37..ea2d9d3e 100644
--- a/app/src/main/java/eu/darken/capod/pods/core/apple/ble/PodDeviceExtensions.kt
+++ b/app/src/main/java/eu/darken/capod/pods/core/apple/ble/PodDeviceExtensions.kt
@@ -21,6 +21,12 @@ import kotlin.math.roundToInt
 
 const val BATTERY_UNKNOWN = -1f
 
+/** Step size of a percent-granularity reading: AAP battery notifications and the encrypted payload. */
+const val BATTERY_RESOLUTION_PERCENT = 0.01f
+
+/** Step size of the public advertisement's battery nibble, which only carries deciles. */
+const val BATTERY_RESOLUTION_DECILE = 0.10f
+
 fun isKnownBattery(percent: Float): Boolean = percent.isFinite() && percent >= 0f
 
 fun batteryProgress(percent: Float): Float =
diff --git a/app/src/main/java/eu/darken/capod/pods/core/apple/ble/devices/DualApplePods.kt b/app/src/main/java/eu/darken/capod/pods/core/apple/ble/devices/DualApplePods.kt
index 07fd298c..4a982bfa 100644
--- a/app/src/main/java/eu/darken/capod/pods/core/apple/ble/devices/DualApplePods.kt
+++ b/app/src/main/java/eu/darken/capod/pods/core/apple/ble/devices/DualApplePods.kt
@@ -4,6 +4,8 @@ import eu.darken.capod.common.debug.logging.log
 import eu.darken.capod.common.isBitSet
 import eu.darken.capod.common.lowerNibble
 import eu.darken.capod.common.upperNibble
+import eu.darken.capod.pods.core.apple.ble.BATTERY_RESOLUTION_DECILE
+import eu.darken.capod.pods.core.apple.ble.BATTERY_RESOLUTION_PERCENT
 import eu.darken.capod.pods.core.apple.ble.DualBlePodSnapshot
 import eu.darken.capod.pods.core.apple.ble.DualBlePodSnapshot.Pod
 
@@ -137,6 +139,13 @@ interface DualApplePods : ApplePods, HasChargeDetectionDual, DualBlePodSnapshot,
             }
         }
 
+    /** The encrypted payload carries whole percents; the public nibble only carries deciles. */
+    override val batteryCaseResolution: Float
+        get() = when {
+            payload.private?.asBatteryState(3) != null -> BATTERY_RESOLUTION_PERCENT
+            else -> BATTERY_RESOLUTION_DECILE
+        }
+
     override val isCaseCharging: Boolean
         get() {
             payload.private?.asBatteryState(3)?.let { return it.isCharging }
diff --git a/app/src/main/java/eu/darken/capod/pods/core/apple/ble/devices/HasCase.kt b/app/src/main/java/eu/darken/capod/pods/core/apple/ble/devices/HasCase.kt
index a196d909..c9695823 100644
--- a/app/src/main/java/eu/darken/capod/pods/core/apple/ble/devices/HasCase.kt
+++ b/app/src/main/java/eu/darken/capod/pods/core/apple/ble/devices/HasCase.kt
@@ -2,14 +2,23 @@ package eu.darken.capod.pods.core.apple.ble.devices
 
 import androidx.annotation.DrawableRes
 import eu.darken.capod.R
+import eu.darken.capod.pods.core.apple.ble.BATTERY_RESOLUTION_DECILE
 
 interface HasCase {
 
     val batteryCasePercent: Float?
 
+    /**
+     * Step size of [batteryCasePercent]. Deciles unless a decoder knows it read a finer source, so
+     * a caller reasoning about how much the true value may exceed the reading errs on the coarse
+     * side.
+     */
+    val batteryCaseResolution: Float
+        get() = BATTERY_RESOLUTION_DECILE
+
     val isCaseCharging: Boolean
 
     @get:DrawableRes
     val caseIcon: Int
         get() = R.drawable.device_airpods_gen1_case
-}
\ No newline at end of file
+}