How Do I get Battery Charge Cycles from a connected iOS device?

How to Retrieve Battery Charge Cycles from a Connected iOS Device

Learn how to programmatically access the battery charge cycle count from an iOS device connected to a macOS machine using MobileDevice.framework.

Understanding the health of an iOS device's battery is crucial for diagnostics, refurbishment, or simply for curious users. One key metric for battery health is the 'charge cycle count'. This article will guide you through the process of programmatically obtaining this information from a connected iOS device using Apple's MobileDevice.framework on macOS. While direct access to this framework is often undocumented and requires careful handling, it provides a powerful way to interact with iOS devices at a lower level than typical public APIs.

Understanding MobileDevice.framework

MobileDevice.framework is a private framework used by macOS applications like Xcode, iTunes, and Finder to communicate with connected iOS devices. It offers a wide range of functionalities, from device detection and information retrieval to app installation and diagnostics. Because it's a private framework, its APIs are not officially documented by Apple and can change with macOS or iOS updates, making development against it somewhat challenging but often necessary for specific tasks like reading battery cycle counts.

flowchart TD
    A[macOS Application] --> B{"Load MobileDevice.framework"}
    B --> C[AMDeviceNotificationSubscribe]
    C --> D{Device Connected?}
    D -- Yes --> E[AMDeviceConnect]
    E --> F[AMDeviceStartSession]
    F --> G[AMDeviceCopyValue(kAMDDeviceBatteryCycleCountKey)]
    G --> H[Retrieve Cycle Count]
    H --> I[AMDeviceStopSession]
    I --> J[AMDeviceDisconnect]
    D -- No --> C
    J --> K[End]

Workflow for retrieving battery cycle count using MobileDevice.framework

Prerequisites and Setup

Before you can interact with MobileDevice.framework, you'll need a macOS development environment. You'll typically be writing code in Objective-C or Swift, and linking against the framework. Since it's private, you'll often need to dynamically load it or use specific linker flags. For this example, we'll assume an Objective-C context, as many existing examples and reverse-engineered headers are in Objective-C.

Key Functions and Data Structures

The core of interacting with MobileDevice.framework involves several key functions and data types. You'll need to subscribe to device notifications, connect to a specific device, start a session, and then query for specific values. The battery cycle count is typically exposed via a key like kAMDDeviceBatteryCycleCountKey or similar, which you might need to discover through reverse engineering or existing community resources.

// Example of dynamically loading MobileDevice.framework
void* MobileDeviceHandle = dlopen("/System/Library/PrivateFrameworks/MobileDevice.framework/MobileDevice", RTLD_LAZY);

// Function pointers for key APIs
typedef int (*AMDeviceNotificationSubscribeFunc)(void (*callback)(struct AMDeviceNotificationInfo *), int, int, void *);
typedef int (*AMDeviceConnectFunc)(struct AMDevice *);
typedef int (*AMDeviceStartSessionFunc)(struct AMDevice *);
typedef CFTypeRef (*AMDeviceCopyValueFunc)(struct AMDevice *, CFStringRef, CFStringRef);
typedef int (*AMDeviceStopSessionFunc)(struct AMDevice *);
typedef int (*AMDeviceDisconnectFunc)(struct AMDevice *);
typedef int (*AMDeviceNotificationUnsubscribeFunc)(int);

AMDeviceNotificationSubscribeFunc AMDeviceNotificationSubscribe = (AMDeviceNotificationSubscribeFunc)dlsym(MobileDeviceHandle, "AMDeviceNotificationSubscribe");
AMDeviceConnectFunc AMDeviceConnect = (AMDeviceConnectFunc)dlsym(MobileDeviceHandle, "AMDeviceConnect");
AMDeviceStartSessionFunc AMDeviceStartSession = (AMDeviceStartSessionFunc)dlsym(MobileDeviceHandle, "AMDeviceStartSession");
AMDeviceCopyValueFunc AMDeviceCopyValue = (AMDeviceCopyValueFunc)dlsym(MobileDeviceHandle, "AMDeviceCopyValue");
AMDeviceStopSessionFunc AMDeviceStopSession = (AMDeviceStopSessionFunc)dlsym(MobileDeviceHandle, "AMDeviceStopSession");
AMDeviceDisconnectFunc AMDeviceDisconnect = (AMDeviceDisconnectFunc)dlsym(MobileDeviceHandle, "AMDeviceDisconnect");
AMDeviceNotificationUnsubscribeFunc AMDeviceNotificationUnsubscribe = (AMDeviceNotificationUnsubscribeFunc)dlsym(MobileDeviceHandle, "AMDeviceNotificationUnsubscribe");

// Define the device notification structure (simplified)
struct AMDeviceNotificationInfo {
    struct AMDevice *device;
    unsigned int msg;
};

// Define the AMDevice structure (opaque, usually just a pointer)
struct AMDevice;

// Callback function for device notifications
void deviceNotificationCallback(struct AMDeviceNotificationInfo *info) {
    if (info->msg == 1) { // Device connected
        NSLog(@"Device connected: %@", info->device);
        // Proceed to connect, start session, and get value
    }
}

// In your main code:
int notificationRef;
AMDeviceNotificationSubscribe(deviceNotificationCallback, 0, 0, NULL, &notificationRef);
CFRunLoopRun(); // Keep the application running to receive notifications

Retrieving the Battery Cycle Count

Once you have a connected device and an active session, you can use AMDeviceCopyValue to query for specific properties. The key for battery cycle count is not always explicitly documented, but common keys include BatteryCycleCount or CycleCount. You might need to experiment or consult community resources to find the exact string literal that works for your target iOS version.

// Inside your deviceNotificationCallback or a dedicated function
void getBatteryCycleCount(struct AMDevice *device) {
    if (AMDeviceConnect(device) == 0) {
        if (AMDeviceStartSession(device) == 0) {
            CFStringRef domain = CFSTR("com.apple.mobile.battery"); // Common domain for battery info
            CFStringRef key = CFSTR("CycleCount"); // This key might vary, try others like "BatteryCycleCount"

            CFTypeRef cycleCountValue = AMDeviceCopyValue(device, domain, key);

            if (cycleCountValue) {
                if (CFGetTypeID(cycleCountValue) == CFNumberGetTypeID()) {
                    long cycleCount;
                    CFNumberGetValue((CFNumberRef)cycleCountValue, kCFNumberLongType, &cycleCount);
                    NSLog(@"Battery Cycle Count: %ld", cycleCount);
                } else if (CFGetTypeID(cycleCountValue) == CFStringGetTypeID()) {
                    NSLog(@"Battery Cycle Count (string): %@", (NSString *)cycleCountValue);
                }
                CFRelease(cycleCountValue);
            } else {
                NSLog(@"Could not retrieve battery cycle count for device.");
            }

            AMDeviceStopSession(device);
        } else {
            NSLog(@"Failed to start session with device.");
        }
        AMDeviceDisconnect(device);
    } else {
        NSLog(@"Failed to connect to device.");
    }
}

1. Set up your macOS project

Create a new macOS command-line tool project in Xcode. Ensure you have the necessary build settings to allow dynamic library loading.

2. Dynamically load MobileDevice.framework

Use dlopen() to load the framework at runtime. This avoids direct linking against a private framework, which can cause issues.

3. Define function pointers

Declare function pointers for the MobileDevice.framework APIs you intend to use (e.g., AMDeviceNotificationSubscribe, AMDeviceConnect, AMDeviceCopyValue). Use dlsym() to get the addresses of these functions.

4. Subscribe to device notifications

Call AMDeviceNotificationSubscribe() with a callback function. This function will be invoked when devices are connected or disconnected.

5. Implement the device callback

In your callback, when a device is connected, call AMDeviceConnect() and AMDeviceStartSession() to establish communication.

6. Query for battery cycle count

Use AMDeviceCopyValue() with the appropriate domain (e.g., com.apple.mobile.battery) and key (e.g., CycleCount) to retrieve the battery cycle count. Handle the returned CFTypeRef and extract the numerical value.

7. Clean up

After retrieving the value, call AMDeviceStopSession() and AMDeviceDisconnect(). Remember to CFRelease() any CFTypeRef objects you obtained.