diff --git a/src/app/admin/rentals/[id]/page.tsx b/src/app/admin/rentals/[id]/page.tsx
index 1ca36cf..4fe5a4a 100644
--- a/src/app/admin/rentals/[id]/page.tsx
+++ b/src/app/admin/rentals/[id]/page.tsx
@@ -128,6 +128,7 @@ const mockRentals: Rental[] = [
     dailyRate: 150,
     weeklyRate: 900,
     monthlyRate: 3500,
+    batteryRent: 1500,
     totalPaid: 38500,
     dueRental: 0,
     pendingRent: 0,
@@ -287,6 +288,23 @@ const mockHubs = [
   { id: 'HUB-004', name: 'Mirpur Hub' },
 ];
 
+interface BatteryOption {
+  id: string;
+  brand: string;
+  model: string;
+  soc: number;
+  monthlyRent: number;
+  status: 'available' | 'in-use';
+}
+
+const mockBatteries: BatteryOption[] = [
+  { id: 'BAT-DH-001', brand: 'Galaxy', model: '72V 45Ah', soc: 85, monthlyRent: 1500, status: 'available' },
+  { id: 'BAT-DH-002', brand: 'Titan', model: '72V 50Ah', soc: 92, monthlyRent: 1800, status: 'available' },
+  { id: 'BAT-DH-003', brand: 'PowerMax', model: '60V 40Ah', soc: 78, monthlyRent: 1200, status: 'available' },
+  { id: 'BAT-DH-004', brand: 'UltraCell', model: '72V 55Ah', soc: 88, monthlyRent: 2000, status: 'available' },
+  { id: 'BAT-DH-005', brand: 'EcoVolt', model: '48V 30Ah', soc: 65, monthlyRent: 800, status: 'available' },
+];
+
 const mockDamageHistory = [
   { id: 'DMG-001', date: '2024-02-10', description: 'Minor scratch on left mirror', severity: 'minor', status: 'resolved' },
   { id: 'DMG-002', date: '2024-03-05', description: 'Front fender dented', severity: 'moderate', status: 'reported' },
@@ -334,6 +352,8 @@ export default function RentalDetailPage() {
   const [documents, setDocuments] = useState(mockDocuments);
   const [showUploadModal, setShowUploadModal] = useState(false);
   const [uploadDocName, setUploadDocName] = useState('');
+  const [showAddBatteryModal, setShowAddBatteryModal] = useState(false);
+  const [selectedBatteryId, setSelectedBatteryId] = useState('');
 
   const [acceptPermission, setAcceptPermission] = useState(false);
   const [rejectPermission, setRejectPermission] = useState(false);
@@ -486,6 +506,31 @@ export default function RentalDetailPage() {
     setRental(prev => prev ? { ...prev, status: 'active', activatedAt: new Date().toISOString().split('T')[0] } : null);
   };
 
+  const handleAddBattery = () => {
+    if (!selectedBatteryId || !rental) return;
+    const battery = mockBatteries.find(b => b.id === selectedBatteryId);
+    if (!battery) return;
+
+    const newBatteryHistory: BatteryRentalHistory = {
+      id: `BAT-RENT-${Date.now()}`,
+      batteryId: battery.id,
+      batteryName: `${battery.brand} ${battery.model}`,
+      assignedAt: new Date().toISOString().split('T')[0],
+      monthlyRent: battery.monthlyRent,
+      status: 'active',
+    };
+
+    setRental(prev => prev ? {
+      ...prev,
+      batteryId: battery.id,
+      batteryName: `${battery.brand} ${battery.model}`,
+      batteryRent: (prev.batteryRent || 0) + battery.monthlyRent,
+      batteryHistory: [...(prev.batteryHistory || []), newBatteryHistory],
+    } : null);
+    setShowAddBatteryModal(false);
+    setSelectedBatteryId('');
+  };
+
   const handleAddNote = () => {
     if (!newNote.trim()) return;
     setNotes(prev => [...prev, { id: `n${Date.now()}`, text: newNote, createdAt: new Date().toISOString().split('T')[0] }]);
@@ -702,12 +747,36 @@ export default function RentalDetailPage() {
                 <div className="space-y-2">
                   <div className="flex justify-between"><span className="text-sm text-slate-600">Type</span><span className="text-sm font-medium text-slate-800 capitalize">{rental.subscriptionType}</span></div>
                   <div className="flex justify-between">
-                    <span className="text-sm text-slate-600">Rate</span>
+                    <span className="text-sm text-slate-600">Bike Rate</span>
                     <span className="text-sm font-medium text-slate-800">
                       ৳{rental.subscriptionType === 'daily' ? rental.dailyRate : rental.subscriptionType === 'weekly' ? rental.weeklyRate : rental.monthlyRate}/
                       {rental.subscriptionType === 'daily' ? 'day' : rental.subscriptionType === 'weekly' ? 'week' : 'month'}
                     </span>
                   </div>
+                  {rental.batteryRent && rental.batteryRent > 0 && (
+                    <>
+                      <div className="flex justify-between">
+                        <span className="text-sm text-amber-600">Battery Rate</span>
+                        <span className="text-sm font-medium text-amber-700">
+                          ৳{Math.round(rental.batteryRent / (rental.subscriptionType === 'daily' ? 30 : rental.subscriptionType === 'weekly' ? 4 : 1))}/
+                          {rental.subscriptionType === 'daily' ? 'day' : rental.subscriptionType === 'weekly' ? 'week' : 'month'}
+                        </span>
+                      </div>
+                      <div className="pt-2 mt-2 border-t border-slate-100">
+                        <div className="flex justify-between">
+                          <span className="text-sm font-medium text-emerald-700">Total (Bike + Battery)</span>
+                          <span className="text-sm font-bold text-emerald-700">
+                            ৳{rental.subscriptionType === 'daily' 
+                              ? rental.dailyRate + Math.round(rental.batteryRent / 30)
+                              : rental.subscriptionType === 'weekly' 
+                                ? rental.weeklyRate + Math.round(rental.batteryRent / 4)
+                                : rental.monthlyRate + rental.batteryRent}/
+                            {rental.subscriptionType === 'daily' ? 'day' : rental.subscriptionType === 'weekly' ? 'week' : 'month'}
+                          </span>
+                        </div>
+                      </div>
+                    </>
+                  )}
                 </div>
               </div>
 
@@ -729,11 +798,16 @@ export default function RentalDetailPage() {
             </div>
 
             {/* Battery Rental History */}
-            {rental.batteryHistory && rental.batteryHistory.length > 0 && (
-              <div className="bg-white p-4 rounded-xl border border-slate-200">
-                <h3 className="font-semibold text-slate-700 mb-3 flex items-center gap-2">
+            <div className="bg-white p-4 rounded-xl border border-slate-200">
+              <div className="flex items-center justify-between mb-3">
+                <h3 className="font-semibold text-slate-700 flex items-center gap-2">
                   <Battery className="w-5 h-5 text-amber-500" /> Battery Rental History
                 </h3>
+                <button onClick={() => setShowAddBatteryModal(true)} className="px-3 py-1.5 bg-amber-600 text-white rounded-lg text-xs font-medium hover:bg-amber-700 flex items-center gap-1">
+                  <Plus className="w-3 h-3" /> Add Battery
+                </button>
+              </div>
+              {rental.batteryHistory && rental.batteryHistory.length > 0 ? (
                 <div className="overflow-x-auto">
                   <table className="w-full">
                     <thead className="bg-slate-50">
@@ -764,14 +838,80 @@ export default function RentalDetailPage() {
                     </tbody>
                   </table>
                 </div>
-                {rental.batteryHistory.some(b => b.status === 'active') && (
-                  <div className="mt-3 p-3 bg-amber-50 border border-amber-200 rounded-lg">
-                    <p className="text-sm text-amber-700">
-                      <span className="font-medium">Active Battery Rent: </span>
-                      ৳{rental.batteryHistory.filter(b => b.status === 'active').reduce((sum, b) => sum + b.monthlyRent, 0)}/month
-                    </p>
+              ) : (
+                <p className="text-sm text-slate-500">No battery assigned yet.</p>
+              )}
+              {rental.batteryHistory?.some(b => b.status === 'active') && (
+                <div className="mt-3 p-3 bg-amber-50 border border-amber-200 rounded-lg">
+                  <p className="text-sm text-amber-700">
+                    <span className="font-medium">Active Battery Rent: </span>
+                    ৳{rental.batteryHistory.filter(b => b.status === 'active').reduce((sum, b) => sum + b.monthlyRent, 0)}/month
+                  </p>
+                </div>
+              )}
+            </div>
+
+            {/* Add Battery Modal */}
+            {showAddBatteryModal && (
+              <div className="fixed inset-0 bg-black/50 flex items-center justify-center z-50 p-4">
+                <div className="bg-white rounded-xl shadow-xl w-full max-w-md">
+                  <div className="p-4 border-b border-slate-100 flex justify-between items-center">
+                    <h3 className="font-semibold text-slate-800">Add Battery to Rental</h3>
+                    <button onClick={() => setShowAddBatteryModal(false)} className="text-slate-400 hover:text-slate-600">
+                      <X className="w-5 h-5" />
+                    </button>
                   </div>
-                )}
+                  <div className="p-4 space-y-4">
+                    <div>
+                      <label className="text-sm text-slate-600 mb-1 block">Select Battery</label>
+                      <select
+                        value={selectedBatteryId}
+                        onChange={(e) => setSelectedBatteryId(e.target.value)}
+                        className="w-full px-3 py-2 border border-slate-200 rounded-lg text-sm"
+                      >
+                        <option value="">Select Battery...</option>
+                        {mockBatteries.map(bat => (
+                          <option key={bat.id} value={bat.id}>{bat.brand} {bat.model} - SOC: {bat.soc}% - Rent: ৳{bat.monthlyRent}/month</option>
+                        ))}
+                      </select>
+                    </div>
+                    {selectedBatteryId && (() => {
+                      const batteryMonthlyRent = mockBatteries.find(b => b.id === selectedBatteryId)?.monthlyRent || 0;
+                      return (
+                        <div className="p-3 bg-amber-50 border border-amber-200 rounded-lg space-y-2">
+                          <p className="text-sm text-amber-700">
+                            Battery Monthly Rent: <span className="font-bold">৳{batteryMonthlyRent}/month</span>
+                          </p>
+                          <div className="text-xs text-amber-600 pt-2 border-t border-amber-100">
+                            <p className="font-medium mb-1">Calculated Rate by Subscription:</p>
+                            <p>• Daily: ৳{Math.round(batteryMonthlyRent / 30)}/day (৳{batteryMonthlyRent}/30)</p>
+                            <p>• Weekly: ৳{Math.round(batteryMonthlyRent / 4)}/week (৳{batteryMonthlyRent}/4)</p>
+                            <p>• Monthly (30 days): ৳{batteryMonthlyRent}/month</p>
+                            <p>• Monthly (31 days): ৳{batteryMonthlyRent}/month</p>
+                          </div>
+                          <div className="pt-2 mt-2 border-t border-amber-100">
+                            <p className="text-xs font-medium text-amber-700">Your Current Subscription: {rental.subscriptionType}</p>
+                            <p className="text-sm font-bold text-amber-800">
+                              You will pay: ৳{rental.subscriptionType === 'daily' 
+                                ? Math.round(batteryMonthlyRent / 30)
+                                : rental.subscriptionType === 'weekly' 
+                                  ? Math.round(batteryMonthlyRent / 4)
+                                  : batteryMonthlyRent}/{rental.subscriptionType}
+                            </p>
+                          </div>
+                        </div>
+                      );
+                    })()}
+                    <div className="flex gap-2 pt-2">
+                      <button onClick={() => setShowAddBatteryModal(false)} className="flex-1 py-2 px-4 border border-slate-200 text-slate-600 rounded-lg text-sm hover:bg-slate-50">
+                        Cancel
+                      </button>
+                      <button onClick={handleAddBattery} disabled={!selectedBatteryId} className="flex-1 py-2 px-4 bg-amber-600 text-white rounded-lg text-sm hover:bg-amber-700 disabled:opacity-50">
+                        Add Battery
+                      </button>
+                    </div>
+                  </div>
+                </div>
               </div>
             )}