diff --git a/app/src/main/java/com/sockenklaus/batterytracker/ui/fragments/add_battery/AddBatteryFragment.kt b/app/src/main/java/com/sockenklaus/batterytracker/ui/fragments/add_battery/AddBatteryFragment.kt
index a76b51c..3d40c1a 100644
--- a/app/src/main/java/com/sockenklaus/batterytracker/ui/fragments/add_battery/AddBatteryFragment.kt
+++ b/app/src/main/java/com/sockenklaus/batterytracker/ui/fragments/add_battery/AddBatteryFragment.kt
@@ -14,17 +14,16 @@ import androidx.compose.runtime.*
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.res.stringResource
-import androidx.compose.ui.text.TextStyle
 import androidx.compose.ui.text.input.KeyboardType
 import androidx.compose.ui.unit.dp
-import androidx.constraintlayout.compose.ConstraintLayout
-import androidx.constraintlayout.compose.Dimension
+import androidx.lifecycle.asLiveData
 import androidx.lifecycle.lifecycleScope
 import com.sockenklaus.batterytracker.R
 import com.sockenklaus.batterytracker.databinding.FragmentAddBatteryBinding
 import com.sockenklaus.batterytracker.room.BatteryTrackerDB
 import com.sockenklaus.batterytracker.room.entities.Battery
 import com.sockenklaus.batterytracker.ui.theme.BatteryTrackerTheme
+import com.sockenklaus.batterytracker.ui.theme.Gray500
 import com.sockenklaus.batterytracker.util.validateDecimal
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.launch
@@ -45,13 +44,26 @@ class AddBatteryFragment : Fragment() {
     ): View {
 
         _binding = FragmentAddBatteryBinding.inflate(inflater, container, false)
+        val db = BatteryTrackerDB.getInstance(requireContext())
         val view = binding.root
 
+        val batteries = db.batteryDao().getBatteries().asLiveData()
+        var listBatteries = emptyList<Battery>()
+
+        batteries.observe(viewLifecycleOwner) {
+            listBatteries = it
+        }
+
         binding.root.setContent {
             BatteryTrackerTheme {
                 var batteryId by remember { mutableStateOf("") }
                 var declaredCapacity by remember { mutableStateOf("")}
 
+                var batteryIsError by remember { mutableStateOf(false) }
+                var batteryHelper: Int? by remember { mutableStateOf(null) }
+                var chargeIsError by remember { mutableStateOf(false) }
+                var chargeHelper: Int? by remember { mutableStateOf(null) }
+
                 val outerPadding = 24.dp
                 val innerPadding = 16.dp
 
@@ -60,9 +72,19 @@ class AddBatteryFragment : Fragment() {
                 ) {
                     MyOutlinedTextField(
                         value = batteryId,
-                        onValueChange = { batteryId = it },
+                        onValueChange = { value ->
+                            batteryId = value
+                            onChangeBatteryId(
+                                value = value,
+                                batteries = listBatteries,
+                                changeHelper = { ch -> batteryHelper = ch },
+                                changeIsError = { ce -> batteryIsError = ce }
+                            )
+                        },
                         labelId = R.string.hint_enter_battery_id,
-                        leadingIcon = { Icon(Icons.Default.Tag, "Icon Tag") }
+                        leadingIcon = { Icon(Icons.Default.Tag, "Icon Tag") },
+                        isError = batteryIsError,
+                        helperTextId = batteryHelper
                     )
 
                     Spacer(Modifier.size(innerPadding))
@@ -72,7 +94,9 @@ class AddBatteryFragment : Fragment() {
                         onValueChange = { declaredCapacity = validateDecimal(it, declaredCapacity) },
                         labelId = R.string.hint_enter_declared_capacity,
                         keyboardOptions = KeyboardOptions(keyboardType = KeyboardType.Decimal),
-                        leadingIcon = { Icon(Icons.Default.BatteryFull, "Icon Battery Full") }
+                        leadingIcon = { Icon(Icons.Default.BatteryFull, "Icon Battery Full") },
+                        isError = chargeIsError,
+                        helperTextId = chargeHelper
                     )
 
                     Spacer(Modifier.size(outerPadding))
@@ -101,23 +125,49 @@ class AddBatteryFragment : Fragment() {
         labelId: Int,
         leadingIcon: (@Composable () -> Unit)? = null,
         isError: Boolean = false,
-        helperText: String = ""
+        helperTextId: Int? = null
     ) {
+        val helperTextColor = if(isError){
+            MaterialTheme.colors.error
+        } else {
+            Gray500
+        }
+
         OutlinedTextField(
             value = value,
             onValueChange = onValueChange,
             keyboardOptions = keyboardOptions,
             label = { Text(stringResource(labelId)) },
             leadingIcon = leadingIcon,
+            isError = isError,
             modifier = Modifier.fillMaxWidth()
         )
         Text(
-            text = helperText,
+            text = stringResource(helperTextId ?: R.string.helper_required),
             style = MaterialTheme.typography.caption,
+            color = helperTextColor,
             modifier = Modifier.padding(start = 16.dp)
         )
     }
 
+    private fun onChangeBatteryId(
+        value: String,
+        batteries: List<Battery>,
+        changeIsError: (Boolean) -> Unit,
+        changeHelper: (Int?) -> Unit
+    ) {
+        changeIsError(false)
+        changeHelper(null)
+        if(batteries.any{ it.id.lowercase() == value.lowercase() }){
+            changeIsError(true)
+            changeHelper(R.string.helper_battery_not_unique)
+        }
+        if(value.isEmpty()){
+            changeIsError(true)
+            changeHelper(null)
+        }
+    }
+
     /*
     TODO: Implement the action
      */
diff --git a/app/src/main/java/com/sockenklaus/batterytracker/ui/theme/Color.kt b/app/src/main/java/com/sockenklaus/batterytracker/ui/theme/Color.kt
index 3870eb0..1227bc9 100644
--- a/app/src/main/java/com/sockenklaus/batterytracker/ui/theme/Color.kt
+++ b/app/src/main/java/com/sockenklaus/batterytracker/ui/theme/Color.kt
@@ -5,4 +5,5 @@ import androidx.compose.ui.graphics.Color
 val Purple200 = Color(0xFFBB86FC)
 val Purple500 = Color(0xFF6200EE)
 val Purple700 = Color(0xFF3700B3)
-val Teal200 = Color(0xFF03DAC5)
\ No newline at end of file
+val Teal200 = Color(0xFF03DAC5)
+val Gray500 = Color(0xFF9E9E9E)
\ No newline at end of file
diff --git a/app/src/main/res/values/strings.xml b/app/src/main/res/values/strings.xml
index dd4ee42..8e76dda 100644
--- a/app/src/main/res/values/strings.xml
+++ b/app/src/main/res/values/strings.xml
@@ -27,4 +27,6 @@
     <string name="declared_capacity">Declared Capacity</string>
     <string name="button_save_battery">Save Battery</string>
     <string name="title_activity_add_battery">AddBattery</string>
+    <string name="helper_required">* Required</string>
+    <string name="helper_battery_not_unique">Battery-ID not unique!</string>
 </resources>
\ No newline at end of file