How to accurately obtain the iPhone battery level?

Question

I want to get the battery level,and Accurate to 1%. I googled and find this,

    CFTypeRef blob = IOPSCopyPowerSourcesInfo();
CFArrayRef sources = IOPSCopyPowerSourcesList(blob);

CFDictionaryRef pSource = NULL;
const void *psValue;

int numOfSources = CFArrayGetCount(sources);
if (numOfSources == 0) {
    NSLog(@"Error in CFArrayGetCount");
    return -1.0f;
}

for (int i = 0 ; i < numOfSources ; i++)
{
    pSource = IOPSGetPowerSourceDescription(blob, CFArrayGetValueAtIndex(sources, i));
    if (!pSource) {
        NSLog(@"Error in IOPSGetPowerSourceDescription");
        return -1.0f;
    }
    psValue = (CFStringRef)CFDictionaryGetValue(pSource, CFSTR(kIOPSNameKey));

    int curCapacity = 0;
    int maxCapacity = 0;
    double percent;

    psValue = CFDictionaryGetValue(pSource, CFSTR(kIOPSCurrentCapacityKey));
    CFNumberGetValue((CFNumberRef)psValue, kCFNumberSInt32Type, &curCapacity);

    psValue = CFDictionaryGetValue(pSource, CFSTR(kIOPSMaxCapacityKey));
    CFNumberGetValue((CFNumberRef)psValue, kCFNumberSInt32Type, &maxCapacity);

    percent = ((double)curCapacity/(double)maxCapacity * 100.0f);

    return percent;
}
return -1.0f;

but it's not accurate. So I am asking for help here.

Answer 1

From UIDevice Class Reference:

You can use the UIDevice instance to obtain information and notifications about changes to the battery’s charge state (described by the batteryState property) and charge level (described by the batteryLevel property).

[UIDevice currentDevice].batteryMonitoringEnabled = YES;
float batteryLevel = [UIDevice currentDevice].batteryLevel;

NSLog(@"battery level: %f", batteryLevel * 100);