Update battery chemistry protocol with new types

- Rename NMC to LiPo as standard for dev boards
- Add 'none' option for external power (wall-powered devices)
- Add lead acid support (12V solar/off-grid setups)
- Protocol: 0x00=none, 0x01=lipo, 0x02=lifepo4, 0x03=leadacid
- Add migration for old stored values (nmc/liion -> lipo)
- Make return type nullable for 'none' chemistry

lib/connector/meshcore_connector.dart

@@ -225,12 +225,12 @@ class MeshCoreConnector extends ChangeNotifier {
     if (_reportedBatteryChemistry != null) return _reportedBatteryChemistry!;
     // Fall back to user setting
     final deviceId = _device?.remoteId.toString();
-    if (deviceId == null || _appSettingsService == null) return 'nmc';
+    if (deviceId == null || _appSettingsService == null) return 'lipo';
     return _appSettingsService!.batteryChemistryForDevice(deviceId);
   }
 
   // Uses shared utility from battery_utils.dart
-  int _estimateBatteryPercent(int millivolts, String chemistry) {
+  int? _estimateBatteryPercent(int millivolts, String chemistry) {
     return estimateBatteryPercent(millivolts, chemistry);
   }
 
@@ -1882,18 +1882,13 @@ class MeshCoreConnector extends ChangeNotifier {
     // [1-2] = battery_mv (uint16 LE)
     // [3-6] = storage_used_kb (uint32 LE)
     // [7-10] = storage_total_kb (uint32 LE)
-    // [11] = battery_chemistry (optional, 0=NMC, 1=LiFePO4, 2=LiPo)
+    // [11] = battery_chemistry (optional: 0=none, 1=lipo, 2=lifepo4, 3=leadacid)
     if (frame.length >= 3) {
       _batteryMillivolts = readUint16LE(frame, 1);
 
       // Check for optional chemistry byte at offset 11 (protocol extension)
       if (frame.length > 11) {
-        final chemByte = frame[11];
-        _reportedBatteryChemistry = switch (chemByte) {
-          0x01 => 'lifepo4',
-          0x02 => 'lipo',
-          _ => 'nmc',
-        };
+        _reportedBatteryChemistry = chemistryFromByte(frame[11]);
       }
 
       final volts = (_batteryMillivolts! / 1000.0).toStringAsFixed(2);

lib/l10n/app_en.arb

@@ -206,9 +206,10 @@
     }
   },
   "appSettings_batteryChemistryConnectFirst": "Connect to a device to choose",
-  "appSettings_batteryNmc": "18650 NMC (3.0-4.2V)",
-  "appSettings_batteryLifepo4": "LiFePO4 (2.6-3.65V)",
-  "appSettings_batteryLipo": "LiPo (3.0-4.2V)",
+  "appSettings_batteryNone": "No Battery (External Power)",
+  "appSettings_batteryLipo": "LiPo (3.7V)",
+  "appSettings_batteryLifepo4": "LiFePO4 (3.2V)",
+  "appSettings_batteryLeadAcid": "Lead Acid (12V)",
   "appSettings_mapDisplay": "Map Display",
   "appSettings_showRepeaters": "Show Repeaters",
   "appSettings_showRepeatersSubtitle": "Display repeater nodes on the map",

lib/l10n/app_localizations.dart

@@ -1108,23 +1108,29 @@ abstract class AppLocalizations {
   /// **'Connect to a device to choose'**
   String get appSettings_batteryChemistryConnectFirst;
 
-  /// No description provided for @appSettings_batteryNmc.
+  /// No description provided for @appSettings_batteryNone.
   ///
   /// In en, this message translates to:
-  /// **'18650 NMC (3.0-4.2V)'**
-  String get appSettings_batteryNmc;
+  /// **'No Battery (External Power)'**
+  String get appSettings_batteryNone;
+
+  /// No description provided for @appSettings_batteryLipo.
+  ///
+  /// In en, this message translates to:
+  /// **'LiPo (3.7V)'**
+  String get appSettings_batteryLipo;
 
   /// No description provided for @appSettings_batteryLifepo4.
   ///
   /// In en, this message translates to:
-  /// **'LiFePO4 (2.6-3.65V)'**
+  /// **'LiFePO4 (3.2V)'**
   String get appSettings_batteryLifepo4;
 
-  /// No description provided for @appSettings_batteryLipo.
+  /// No description provided for @appSettings_batteryLeadAcid.
   ///
   /// In en, this message translates to:
-  /// **'LiPo (3.0-4.2V)'**
-  String get appSettings_batteryLipo;
+  /// **'Lead Acid (12V)'**
+  String get appSettings_batteryLeadAcid;
 
   /// No description provided for @appSettings_mapDisplay.
   ///

lib/l10n/app_localizations_bg.dart

@@ -548,13 +548,16 @@ class AppLocalizationsBg extends AppLocalizations {
       'Свържете се с устройство, за да изберете.';
 
   @override
-  String get appSettings_batteryNmc => '18650 NMC (3.0-4.2V)';
+  String get appSettings_batteryNone => 'No Battery (External Power)';
+
+  @override
+  String get appSettings_batteryLipo => 'Литиев полимер (3.0-4.2V)';
 
   @override
   String get appSettings_batteryLifepo4 => 'Литиево желязо фосфат (2.6-3.65V)';
 
   @override
-  String get appSettings_batteryLipo => 'Литиев полимер (3.0-4.2V)';
+  String get appSettings_batteryLeadAcid => 'Lead Acid (12V)';
 
   @override
   String get appSettings_mapDisplay => 'Карта за показване';

lib/l10n/app_localizations_de.dart

@@ -545,13 +545,16 @@ class AppLocalizationsDe extends AppLocalizations {
       'Verbinde ein Gerät, um zu wählen';
 
   @override
-  String get appSettings_batteryNmc => '18650 NMC (3,0–4,2 V)';
+  String get appSettings_batteryNone => 'No Battery (External Power)';
+
+  @override
+  String get appSettings_batteryLipo => 'LiPo (3,0–4,2V)';
 
   @override
   String get appSettings_batteryLifepo4 => 'LiFePO4 (2,6–3,65 V)';
 
   @override
-  String get appSettings_batteryLipo => 'LiPo (3,0–4,2V)';
+  String get appSettings_batteryLeadAcid => 'Lead Acid (12V)';
 
   @override
   String get appSettings_mapDisplay => 'Kartendarstellung';

lib/l10n/app_localizations_en.dart

@@ -540,13 +540,16 @@ class AppLocalizationsEn extends AppLocalizations {
       'Connect to a device to choose';
 
   @override
-  String get appSettings_batteryNmc => '18650 NMC (3.0-4.2V)';
+  String get appSettings_batteryNone => 'No Battery (External Power)';
 
   @override
-  String get appSettings_batteryLifepo4 => 'LiFePO4 (2.6-3.65V)';
+  String get appSettings_batteryLipo => 'LiPo (3.7V)';
 
   @override
-  String get appSettings_batteryLipo => 'LiPo (3.0-4.2V)';
+  String get appSettings_batteryLifepo4 => 'LiFePO4 (3.2V)';
+
+  @override
+  String get appSettings_batteryLeadAcid => 'Lead Acid (12V)';
 
   @override
   String get appSettings_mapDisplay => 'Map Display';

lib/l10n/app_localizations_es.dart

@@ -546,13 +546,16 @@ class AppLocalizationsEs extends AppLocalizations {
       'Conéctate a un dispositivo para elegir';
 
   @override
-  String get appSettings_batteryNmc => '18650 NMC (3.0-4.2V)';
+  String get appSettings_batteryNone => 'No Battery (External Power)';
+
+  @override
+  String get appSettings_batteryLipo => 'LiPo (3.0-4.2V)';
 
   @override
   String get appSettings_batteryLifepo4 => 'LiFePO4 (2.6-3.65V)';
 
   @override
-  String get appSettings_batteryLipo => 'LiPo (3.0-4.2V)';
+  String get appSettings_batteryLeadAcid => 'Lead Acid (12V)';
 
   @override
   String get appSettings_mapDisplay => 'Visualización del Mapa';

lib/l10n/app_localizations_fr.dart

@@ -548,13 +548,16 @@ class AppLocalizationsFr extends AppLocalizations {
       'Connectez un appareil pour choisir';
 
   @override
-  String get appSettings_batteryNmc => '18650 NMC (3,0-4,2V)';
+  String get appSettings_batteryNone => 'No Battery (External Power)';
+
+  @override
+  String get appSettings_batteryLipo => 'LiPo (3,0-4,2V)';
 
   @override
   String get appSettings_batteryLifepo4 => 'LiFePO4 (2,6-3,65V)';
 
   @override
-  String get appSettings_batteryLipo => 'LiPo (3,0-4,2V)';
+  String get appSettings_batteryLeadAcid => 'Lead Acid (12V)';
 
   @override
   String get appSettings_mapDisplay => 'Affichage de la carte';

lib/l10n/app_localizations_it.dart

@@ -545,13 +545,16 @@ class AppLocalizationsIt extends AppLocalizations {
       'Connetti a un dispositivo per scegliere';
 
   @override
-  String get appSettings_batteryNmc => '18650 NMC (3,0-4,2V)';
+  String get appSettings_batteryNone => 'No Battery (External Power)';
+
+  @override
+  String get appSettings_batteryLipo => 'LiPo (3,0-4,2V)';
 
   @override
   String get appSettings_batteryLifepo4 => 'LiFePO4 (2,6-3,65V)';
 
   @override
-  String get appSettings_batteryLipo => 'LiPo (3,0-4,2V)';
+  String get appSettings_batteryLeadAcid => 'Lead Acid (12V)';
 
   @override
   String get appSettings_mapDisplay => 'Visualizzazione Mappa';

lib/l10n/app_localizations_nl.dart

@@ -543,13 +543,16 @@ class AppLocalizationsNl extends AppLocalizations {
       'Verbind met een apparaat om te selecteren';
 
   @override
-  String get appSettings_batteryNmc => '18650 NMC (3,0-4,2V)';
+  String get appSettings_batteryNone => 'No Battery (External Power)';
+
+  @override
+  String get appSettings_batteryLipo => 'LiPo (3,0-4,2V)';
 
   @override
   String get appSettings_batteryLifepo4 => 'LiFePO4 (2,6-3,65V)';
 
   @override
-  String get appSettings_batteryLipo => 'LiPo (3,0-4,2V)';
+  String get appSettings_batteryLeadAcid => 'Lead Acid (12V)';
 
   @override
   String get appSettings_mapDisplay => 'Kaartweergave';

lib/l10n/app_localizations_pl.dart

@@ -548,13 +548,16 @@ class AppLocalizationsPl extends AppLocalizations {
       'Połącz się z urządzeniem, aby wybrać';
 
   @override
-  String get appSettings_batteryNmc => '18650 NMC (3,0-4,2V)';
+  String get appSettings_batteryNone => 'No Battery (External Power)';
+
+  @override
+  String get appSettings_batteryLipo => 'LiPo (3,0-4,2V)';
 
   @override
   String get appSettings_batteryLifepo4 => 'LiFePO4 (2,6-3,65 V)';
 
   @override
-  String get appSettings_batteryLipo => 'LiPo (3,0-4,2V)';
+  String get appSettings_batteryLeadAcid => 'Lead Acid (12V)';
 
   @override
   String get appSettings_mapDisplay => 'Wyświetlanie mapy';

lib/l10n/app_localizations_pt.dart

@@ -547,13 +547,16 @@ class AppLocalizationsPt extends AppLocalizations {
       'Conecte-se a um dispositivo para escolher';
 
   @override
-  String get appSettings_batteryNmc => '18650 NMC (3,0-4,2V)';
+  String get appSettings_batteryNone => 'No Battery (External Power)';
+
+  @override
+  String get appSettings_batteryLipo => 'LiPo (3,0-4,2V)';
 
   @override
   String get appSettings_batteryLifepo4 => 'LiFePO4 (2,6-3,65V)';
 
   @override
-  String get appSettings_batteryLipo => 'LiPo (3,0-4,2V)';
+  String get appSettings_batteryLeadAcid => 'Lead Acid (12V)';
 
   @override
   String get appSettings_mapDisplay => 'Exibição do Mapa';

lib/l10n/app_localizations_ru.dart

@@ -546,13 +546,16 @@ class AppLocalizationsRu extends AppLocalizations {
       'Подключитесь к устройству, чтобы выбрать';
 
   @override
-  String get appSettings_batteryNmc => '18650 NMC (3.0–4.2 В)';
+  String get appSettings_batteryNone => 'No Battery (External Power)';
+
+  @override
+  String get appSettings_batteryLipo => 'LiPo (3.0–4.2 В)';
 
   @override
   String get appSettings_batteryLifepo4 => 'LiFePO4 (2.6–3.65 В)';
 
   @override
-  String get appSettings_batteryLipo => 'LiPo (3.0–4.2 В)';
+  String get appSettings_batteryLeadAcid => 'Lead Acid (12V)';
 
   @override
   String get appSettings_mapDisplay => 'Отображение карты';

lib/l10n/app_localizations_sk.dart

@@ -540,13 +540,16 @@ class AppLocalizationsSk extends AppLocalizations {
       'Pripojte sa k zariadeniu na výber';
 
   @override
-  String get appSettings_batteryNmc => '18650 NMC (3,0-4,2V)';
+  String get appSettings_batteryNone => 'No Battery (External Power)';
+
+  @override
+  String get appSettings_batteryLipo => 'LiPo (3,0-4,2V)';
 
   @override
   String get appSettings_batteryLifepo4 => 'LiFePO4 (2,6–3,65V)';
 
   @override
-  String get appSettings_batteryLipo => 'LiPo (3,0-4,2V)';
+  String get appSettings_batteryLeadAcid => 'Lead Acid (12V)';
 
   @override
   String get appSettings_mapDisplay => 'Zobrazenie mapy';

lib/l10n/app_localizations_sl.dart

@@ -542,13 +542,16 @@ class AppLocalizationsSl extends AppLocalizations {
       'Za izbiro se poveži z napravo';
 
   @override
-  String get appSettings_batteryNmc => '18650 NMC (3,0-4,2V)';
+  String get appSettings_batteryNone => 'No Battery (External Power)';
+
+  @override
+  String get appSettings_batteryLipo => 'LiPo (3,0-4,2V)';
 
   @override
   String get appSettings_batteryLifepo4 => 'LiFePO4 (2,6–3,65 V)';
 
   @override
-  String get appSettings_batteryLipo => 'LiPo (3,0-4,2V)';
+  String get appSettings_batteryLeadAcid => 'Lead Acid (12V)';
 
   @override
   String get appSettings_mapDisplay => 'Prikaz zemljevida';

lib/l10n/app_localizations_sv.dart

@@ -537,13 +537,16 @@ class AppLocalizationsSv extends AppLocalizations {
       'Anslut till en enhet för att välja';
 
   @override
-  String get appSettings_batteryNmc => '18650 NMC (3.0-4.2V)';
+  String get appSettings_batteryNone => 'No Battery (External Power)';
+
+  @override
+  String get appSettings_batteryLipo => 'LiPo (3.0-4.2V)';
 
   @override
   String get appSettings_batteryLifepo4 => 'LiFePO4 (2,6–3,65V)';
 
   @override
-  String get appSettings_batteryLipo => 'LiPo (3.0-4.2V)';
+  String get appSettings_batteryLeadAcid => 'Lead Acid (12V)';
 
   @override
   String get appSettings_mapDisplay => 'Kartvisning';

lib/l10n/app_localizations_uk.dart

@@ -544,13 +544,16 @@ class AppLocalizationsUk extends AppLocalizations {
       'Підключіть пристрій, щоб вибрати';
 
   @override
-  String get appSettings_batteryNmc => '18650 NMC (3.0-4.2В)';
+  String get appSettings_batteryNone => 'No Battery (External Power)';
+
+  @override
+  String get appSettings_batteryLipo => 'LiPo (3.0-4.2В)';
 
   @override
   String get appSettings_batteryLifepo4 => 'LiFePO4 (2.6-3.65В)';
 
   @override
-  String get appSettings_batteryLipo => 'LiPo (3.0-4.2В)';
+  String get appSettings_batteryLeadAcid => 'Lead Acid (12V)';
 
   @override
   String get appSettings_mapDisplay => 'Відображення карти';

lib/l10n/app_localizations_zh.dart

@@ -517,13 +517,16 @@ class AppLocalizationsZh extends AppLocalizations {
   String get appSettings_batteryChemistryConnectFirst => '连接到设备以进行选择';
 
   @override
-  String get appSettings_batteryNmc => '18650 型号，NMC 电池（3.0-4.2V）';
+  String get appSettings_batteryNone => 'No Battery (External Power)';
+
+  @override
+  String get appSettings_batteryLipo => '锂离子电池 (3.0-4.2V)';
 
   @override
   String get appSettings_batteryLifepo4 => '磷酸铁锂 (2.6-3.65V)';
 
   @override
-  String get appSettings_batteryLipo => '锂离子电池 (3.0-4.2V)';
+  String get appSettings_batteryLeadAcid => 'Lead Acid (12V)';
 
   @override
   String get appSettings_mapDisplay => '地图展示';