In December 2011, I purchased the iPad 2 and integrated it deeply into my workflow. Since then I’ve saved energy by not turning on my main PC for most of my tasks, improved my posture—not sitting on the same chair for hours—thus reducing my chronic back pain, made my experience (browsing, reading, writing, watching) more interactive and fun, and I’ve spent less time on the Internet. A thing that I’ve been obsessing over is battery life. I want to discuss about the battery more.
The battery life of my iPad 2 has been excellent. Prior to that I used an iPhone 3G that didn’t conserve much battery and in short, it sucked. The advertised battery life for the iPad 2 is at ten hours on a single charge. That makes it more efficient than any laptop — and most netbooks — on the market today. I’ve been able to squeeze eleven, hell even twelve, hours on a single charge.
I want to present to you the results of some experiments that I conducted. Aside from the conventional tips for saving battery life, I’ll discuss some other tips I came up with.
Conventional tips for conserving battery life
Here are the tips that even my grandma knows:
- Lower the brightness of the screen
- Switch off 3G and use WiFi when possible
- Switch off Bluetooth when not in use
- Minimise the use of location services
- Turn off push notifications
- Turn off push main (or fetch mail less frequently)
- Turn off EQ when listening to songs
- Do less CPU intensive tasks (like watching movies or reading). Don’t constantly switch between apps
- Set to lock the screen automatically (auto-lock)
- Turn off device if not used for long time
- Charge battery 100% and let it run completely (shuts down) at least once per month
- Disconnect the device once it has charged completely (thus prolonging battery life)
Advanced battery experiments
Aside from the aforementioned tips, I wanted to test some other scenarios and what effect they have on battery life. I couldn’t find any mentions of these particular scenarios over the Internet, so I decided to test them myself. The scenarios that I tested were:
- Scenario 1: In sleep mode: apps running in the background with WiFi on VS apps in the background with WiFi off
- Scenario 2: In sleep mode: apps running in the background VS no apps in the background
- Scenario 3: App left on screen when in sleep mode VS app minimised (background) when in sleep mode
The apps that were selected for this experiment were: Twitter, Facebook, Flipboard, Mail, Safari. For the Mail app I had “fetch new data” turned off (no mail fetched automatically). All other apps had push notifications enabled. Bluetooth was turned off at all times, location services was enabled and brightness was at a minimum. The tests were conducted over a period of 4 days, with battery life at 70% (charging the battery up to that point throughout the day). All the tests were conducted at night from 12:00 AM to 10:00 AM (10 hours).
For the first scenario, it’s better to have WiFi turned off even if you have apps running in the background. When apps were running with WiFi turned on, it consumed a total of 3% of the battery in 10 hours, whereas when apps were running with WiFi turned off it consumed around 0.5% (no change in percentage through the night, but once iPad was used for a couple of minutes, percentage dropped faster).
Results were similar to the previous scenario: it’s better to have no apps running in the background but the fact of having running apps in the background consumed very little power (around 0.5%).
I further investigated this issue and it turns up that the iOS “freezes” the app when it’s minimised (background) and little activity is allowed (push notifications) and once you click on the app, it becomes “unfreezed” and fully working again. So, when double tapping the home button you basically have a list of recently used apps, not a list of running apps in the background. I now, contrary to the past, find it useless going every once in a while and removing all those apps from the list.
Even if you leave an app running on screen once the device is put to sleep it makes no difference on the battery life. The main application used in this test, along with the others running in the background, was Kindle.
I hope you found these tests useful . The way I like to preserve battery, aside from the tips expressed in this post, is turning the Airplane mode on when I won’t be using the device for a long time (at night, before going to sleep). This takes care of turning my WiFi and Bluetooth off.
I managed to squeeze even more battery life from my device (up to 12 hours) when reading. The Kindle app has a brightness slider that reduces the brightness of the screen even more. Moreover, it also allows you to set your reading preferences to white text on black background, a preference which should conserve even more battery. I would love to have those features incorporated in iBooks as well (Update: Now you can customise iBook as well).
When watching an hour-long documentary on YouTube (via WiFi streaming), with the brightness at a minimum and Bluetooth off, the battery percentage only dropped by 7,5%-8%. Let me do the math for you: 12 hours X 8% = 96%. That leaves you battery life to also update your Facebook and Twitter accounts, and also check your emails (device turns off when it reaches 1-2% battery life).
Finally, I found out that when charging the battery, it takes some time for the battery to charge completely, from 98% to 100%. If you leave your device plugged in a bit more it will charge beyond 100% (even if it still says 100%).
Now, if the iPad was more powerful (CPU-wise), I could completely ditch my main bulky workstation that I still use for my photo editing (Photoshop) and video editing (After Effects/Premiere) needs. I was a bit disappointed with the release of the iPad 3 because it didn’t have an awesome quad-core powerful CPU. Not only that, but the retina display, a whooping 2048-by-1536 resolution, is a resource killer making the iPad 3 not much faster than its predecessor, the iPad 2.
If I were Apple, seeing the massive success the iPad has gained, I’d be looking at eliminating the laptops out of the equation. As you can see from the graph above, even without a powerful device that would suit my needs, they beat other laptop manufacturers in sales.
But I’m not Apple nor Tim Cook to order the production of a beasty iPad (CPU/RAM-wise), and it seems that they have different goals in prospect, like releasing an iPad Mini to compete with Amazon’s and Kindle…