Incredible Battery Life

I’ve publicly praised Apple for its honesty in reporting battery life over the past couple of years, and the iPhone 4 gives me no reason to stop.

The 4 has an integrated 5.25Whr battery. That’s around 95% of the battery capacity of the HTC EVO 4G, despite having much lower power frequirements. It’s also a 16% increase over the 4.51Whr battery that was in the iPhone 3GS. This means at bare minimum, assuming the iPhone 4 doesn’t draw any more power than the 3GS, we should get 16% more battery life.

In reality, we get much more.

When Apple introduced the iPhone 3G it dropped battery life to a level that we’d been stuck at ever since. The 3GS improved battery life a bit through better CPU power efficiency but you still didn’t have enough juice to get through a day without charging.

The iPhone 4 changes all of that. The combination of a larger battery and a more power efficient SoC results in an incredible amount of battery life.

Our first test is a basic web browsing benchmark. We've scripted almost two dozen webpages to load, pause for 20 seconds, then forward on to the next page. None of the pages use any Flash. This process repeats until the battery is dead. Screen brightness on the iPhones was set to 50% and the screens remained on the whole time.

Battery life improved nearly 38% with the iPhone 4. It's clear that while the A4 improved performance, the real improvement was in battery life. This test has enough idle time where good power management and low idle power can really impact the results. There's simply no other similar smartphone that can touch the 4's battery life.

We then repeated the same test over WiFi instead of 3G:

Apple claims the iPhone 4 will last for up to 10 hours over WiFi, we measured just under that at 9.96 hours. The improvement here is only 12.8%, which tells me that we're nearing the limit of how efficiently Apple can manage power in WiFi mode. There's a wall that we're quickly approaching with this current architecture.

To measure talk time we play MP3s on repeat into the mic of a phone and use it to call the phone being tested. The process continues until the test phone dies. In this case the screen is allowed to go to sleep, as it normally would be if you were talking on the phone:

Apple promised up to 7 hours of 3G talk time with the iPhone 4. We measured 7.47 hours. That's an increase of 54.9% over the iPhone 3GS. While in a phone call the majority of the A4 SoC is powered down, so the efficiency improvements here have to do with how much less power the A4 consumes while off and the new Skyworks 3G modem (the iPhone 3GS used an Infineon modem).

In our iOS 4 review we looked at the impact multitasking had on the iPhone 3GS' web browsing battery life. I ran our 3G web browsing test while playing music through Pandora in the background. I repeated the test with the iPhone 4 for today's article:

We actually see our largest battery life improvement in this test. With a 57.7% increase in battery life over the 3GS, the iPhone 4 is not only more efficient at idle workloads but also when the SoC is constantly busy. The A4 SoC is rumored to be built on a 45nm process compared to the 65nm SoC used in the 3GS. With a moderate increase in clock speed we should be seeing a lot of the power savings that a full node shrink brings to the table.

The battery life offered by the iPhone 4 is spectacular. My iPhone 3GS could hardly get through a full day of work while traveling, I'd always need to hunt for an outlet before heading into my dinner meeting. I'm about to take my first trip with the iPhone 4 but I get the feeling that I might finally be able to make it through dinner.

Early reports of 20 and 30 hours of battery life are simply exaggerated. They're only possible if you let the phone idle in your pocket for the majority of that time. In other words, if you don't use the phone it lasts for a long time. While that's a testament to the platform's incredible idle power, the real world usage is good enough to stand on its own. It's better than any iPhone or Android phone I've tested thus far.

Performance An iPhone with Bumpers


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  • MisterQED - Wednesday, October 20, 2010 - link

    I am not a member of the “tin foil hat” crowd, I’m a guy with a physics degree and a Ham license, so I know a bit about radios. What I am about to point out seems so obvious to me, but I have never heard it discussed anywhere. Your article discusses the effects of having a exposed antenna as it effects phone reception, but that misses the main point, this is a receiving and transmitting antenna. Having skin contact with a transmitting antenna is not safe. Allow me to explain my thought process and tell me if I have a flaw in my logic.

    1) Constant irritation causes cancer. Whether it is fiberglass fibers, silica dust or coal dust in our lungs, to UV radiation from skin exposed to the sun, if you irritate an area consistently for long periods of time, you are just asking for cancer.

    2) RF radiation from most phones is a subject of worry and present discussion, but it doesn’t worry me. RF radiation is a worry because it will cause electrical conduction thru body tissue. This would be an irritation and consistent irritation can lead to cancer. RF radiation from most phones has two methods of conduction, capacitive and inductive.

    a) Capacitive needs: a sizable area, small dielectric distances and high frequencies. Cell phones have the high frequencies, but all other designs keep minimal gaps between antennas and the operator’s skin. Also the operator’s finger tips provide a rather small area to support capacitive conductance.

    b) Inductive conduction needs frequency matched radiators to allow conduction i.e. a good antenna on each end. Body parts make poor antennas, and bodily dimensions generally don’t match the proportions of ideal radiators, so inductive conduction isn’t really a worry.

    3) iPhone 4s, unlike any previous device, allow a third and a magnitude more effective connection between an operator and a transmitting antenna, a resistive connection. All a resistive connection needs is a low resistance, which skin has when sweaty or damp and the antenna has if it is not covered by a non-conductive coating. To add insult to injury, this contact de-tunes the antenna making it less efficient. This inefficiency causes the transmitter to up the power output as cell phones work on a “yell loud enough to be heard” system, so the worse the reception the more power the phone will pump into the antenna to be able to communicate with the cell tower.

    So unless you can show me where my logic has lead me astray, I would expect that in the future some percentage of the population that use an iPhone without a case may find a small possibly cancerous mole forming on one of their fingertips.

    That is a bigger problem than some dropped calls, so why didn’t you mention it.
  • smithpercy - Sunday, November 14, 2010 - link

    Does this mean that I could cold weld a suitable socket to the gsm antenna side strip to allow a patch cable to an external antenna and get reception in the very marginal areas that I spend most of my time in?? I know that the shield would have to be grounded but that could be done thru one of the other connectors. I understand that would void the warranty, and give apple a conniption fit but that is their problem. Reply
  • keri - Thursday, February 24, 2011 - link

    serious question here. Reply
  • Rizi - Friday, July 13, 2012 - link

    The iPhone 4S doesn't offer much in the way of camera controls. The sensitivity settings, white balance and exposure, for example, are all set automatically with no way of adjusting them prior to taking a shot. There's not even an exposure compensation facility to tweak the exposure. A camera manufacturer wouldn't be able to sell a compact camera with such a limited level of control unless it was for a child. However, it does make the camera of this <a href=" very easy to use and of course extra functionality can be added via apps. One useful option that is available is the ability to manually select whether the flash fires or not. Those who prefer to handover complete control can leave this set to 'Auto' - and generally we found it fired at the correct points, often appearing to improve shots we considered already well-lit. The flash is weak, but it's useful for illuminating very dark scenes or adding a little sparkle to eyes in daylight. It's a very small light source, so if it is the main one for an image, expect strong shadows and highlights – it's not the most flattering option for a night-time portrait, but very strong for a single LED. A tap of the screen is all that is required to set the focus point. The camera then usually does a quick backwards and forwards focus adjustment before the subject is made sharp. There's no clear focus indicator, the subject just looks sharp when the focussing has completed. Although the touchscreen is core to the iPhone, Apple hasn't given the camera a touch-shutter facility. This would trigger than camera to focus and take the shot with a single touch of the screen. Instead, after choosing the focus point, the shutter icon needs to be hit to take the shot. The 'up' volume control can now also be used as the camera shutter button too - however, it was very stiff indeed on our test sample, meaning there was an element of shakiness about some of the photos that simply pressing the screen could accomplish. However, it's still a nice touch to have - taking pictures of yourself is much easier with this as an option. Although there is no optical zoom facility, the iPhone 4s camera allows users to zoom digitally into the scene using the pinch to zoom option on the touchscreen. Plus you could always look SUPER COOL and get one of those optical attachments for the iPhone 4S to make it into a longer range shooting device - but you'd have to be really dedicated to do that. Rather than reducing the size of the images, however, the iPhone interpolates the digitally-zoomed shots so they have the same 3264x2448 pixel dimensions. On-screen icons provide access to the secondary camera and the grid display, flash and HDR options. These icons can be difficult to see when you're shooting from an awkward angle and it's easy to touch one accidentally when you are trying to set the focus point. It's helpful that, if the camera is active when the iPhone 4S is put into sleep mode, the camera is available as soon as the lock screen is swiped open. You can also jump straight into the camera from the lock screen with a double tap of the Home Button, although you can only see the snaps you've taken from that session, meaning you can't sneak into the photo gallery of a code-locked iPhone. Reply
  • Rizi - Tuesday, July 17, 2012 - link

    When Apple announced the new Siri software for the <a href=" 4s</a> it was easy to just dismiss it as another company trying to get on board with the voice recognition gimmick we've seen companies trying to make work for years. But there are a couple of things to remember here: firstly, this is Apple, a brand that will always make something seem cool and work pretty well. And secondly, it's not a technology that it's had to develop fully in house, with the company buying voice recognition development app-maker Siri. We've played with some pretty advanced voice recognition software on the likes of the Samsung Galaxy S2, so we've also taken a look to see how the same command is registered on both phones. Long pressing the home button will result in the Siri voic icon popping up - or alternatively, you can set the iPhone 4S to activate the service when you hold the phone up to your ear in standby mode, so you don't look as ridiculous when talking to your handset. From there, you've got quite a range of things you can achieve with speech alone, be it sending a message, playing a song (or even a playlist), setting the alarm, creating a reminder... we were very impressed with the range of options on offer. And the system is quick too - where with many other phones you have to open up the voice recognition function (often in a long winded way) and then wait for the beep to speak, Siri opens up in around a couple of seconds from anywhere in the phone. The voice recognition is pretty darn good too - we were straight away impressed with how many phrases it managed to get right on the first go, including some pretty obscure bits and pieces of speech. You do have to pronounce your words a little more clinically than you might do normally, but even garbled speech comes through pretty well. To put a number on it: we went through the list of functions Siri offers, and found that around one in three or four attempts went awry, which is miles better than the one in two we encounter on most other phones. However, before we get into the comparison, we should say this about Siri in the UK - the full range of services aren't available, and that's a real shame. This means you can't ask where the nearest McDonald's or petrol station is, a feature that's been talked up in the US. We do have high hopes that the same features will eventually be enabled in the UK, as it's just a matter of licensing the information and incorporating it into the system, but it will be annoying for a number of users to see that Siri comes back with 'I cannot do that' time and time again for cool functionality. But what it does do well is work out the context of what you're saying, something that most other voice recognition software fails to do. So if you say 'Tell Andy his hair looks amazing today' it will work out that you'll want to tell him by message, rather than asking what method you'd prefer to speak to him. Messaging isn't as straightforward as we'd like though, as using the 'Send message' command to a person in your address book will result in you being asked whether you'd like to do it using the phone number or email address - and there's no way to set a personalized choice. Reply

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