Suggestions for Optimizing Battery Life in Mobile Devices

November 22, 2006

I found this article that I wrote for a local techie magazine a couple of years ago on mobile power and battery life. The devices are old, but the suggestions are still valid. Unfortunately, its a pretty long article. Happy reading…


Published in mPH Magazine – July 20, 2004
by Christopher H. Cheng

This month’s Primer was supposed to be on batteries for mobile devices. However, I have taken the liberty of stretching the original concept of this article to a topic that I believe is quite a bit more useful in daily life – Power. All mobile devices today are faced with a number of limitations, CPU speed, hard disk space, memory, video and sound quality, network connectivity, and others. However, the critical factor of battery life often remains overlooked by many mobile device buyers. This article will briefly discuss power or battery life as it relates to the individual’s purchasing decision for a new mobile device and will likewise talk about my experiences as a mobile user focusing on power conservation and things I’ve picked up over the years on the topic.

Life is Always a Balance

In general, the smarter a mobile device gets, the more important battery life fits into the buying decision. The important thing to know about mobile devices is that there is always a trade off somewhere – a flash memory based MP3 player will always have better battery life than a higher capacity, hard disk based iPod, a lower CPU and lighter OS based Palm or BlackBerry would generally have better battery life than a fast, powerful, but heavy OS based PocketPC, while a basic cellphone would almost always have better battery life than these hot, new, full featured smartphones. With notebooks, it’s a little different because the balancing act is made on two dimensions, size and power. In general, big notebooks with those 17 inch screens and 3 GHz processors may be really cool to look at and use, but due to the power requirements of driving such a high spec device, usually have less battery life. The thinking of the manufacturers is that these behemoths would generally not be very portable anyway. On the other hand, an ultraportable is very different. Computing power is often sacrificed for weight, form factor, battery life, heat dissipation capability, and size. Business notebooks (sometimes called “thin and light” models), on the other hand really balance out the manufacturers’ product offering.

So why is this bit of knowledge useful for purposes of this discussion? Simply put, the mobile device buyer should be aware of the features and limitations of the device he wishes to purchase to enable him to make an informed comparison and decision based on his intended use. When people think of buying their next mobile device, whether it is a mobile phone, a notebook, a PDA or PDA-Phone, or other similar devices, more often than not, the first things people check are CPU speed, memory, disk capacity, screen size and resolution, built-in cameras, Bluetooth, WIFI, physical appearance or style, and other similar features. Battery life is generally overlooked completely or would fall within the second or third tier of the purchase criteria. Again, while mobile devices are getting smarter and arguably more PC-like with every release, it is dangerous to base buying decisions of these devices on a PC based purchase-decision model, as there is one major difference between mobile devices and PCs: the mobile device user simply does not have access to something that a PC user would take for granted – immediate availability of a power outlet.

Therefore, the game of mobile power really starts by the buyer internalizing what exactly he wants to do with the mobile device and should base his product purchase from there. For instance, I have a desktop in the office but need a second computer for work. I am often mobile both here and abroad but would generally just use my notebook for presentations, demos, note talking, surfing, and email. I therefore switched to a Mac because it provided a balance of mobility, power, excellent battery life, a fresh, new user experience, while still keeping full compatibility to my windows based network. From a PDA-Phone perspective, I needed a device that I could use heavily for voice, SMS, and particularly corporate email. Again, battery life was pretty important because I am usually mobile (either in a meeting room in the building or outside the office) and a heavy cellphone user for both voice and data. I selected the Treo 600 as it had the qwerty keyboard for SMS and email, had basic PIM functionality I needed in an acceptable, but not exceptional, color screen, and had 6 hours of talktime which is excellent for a PDA-Phone device. Had a wanted to listen to MP3s, watched videos, take pictures, worked with email attachments, and have easy access to a power outlet, I would have probably chosen a PocketPC Phone. I am now using a BlackBerry device because my PDA-Cellphone use profile has not changed but the BlackBerry provides much better power management and the critical BlackBerry push email and OTA calendar sync provided by GlobeSolutions.

Bottom line is not just to study the products out there before you buy, but more importantly to determine exactly what you will use the device for and narrow down your search and compare mobile devices that fit your usage profile (now and in the near future). As a more extreme example, I carry a personal cellphone line as well, used simply to contact friends or family via voice and SMS. All I use is a Nokia 8310 for this and I have been satisfied for years.

Interesting devices I am looking at to fit my profile are the following:
SE K700i – I understand that battery life is not great but I will only use it for my extra line and connectivity for GPRS with my Mac.

PalmOne Treo 600 – The first usable PDA-Phone device in my book with excellent battery life, qwerty keyboard, available corporate email services from Globe, and decent screen. It has some support for multimedia which is unimportant for me.
BlackBerry 7230 – My current device of choice because of the excellent battery life, qwerty keyboard, premium corporate email and calendaring solution from Globe. A zero frills device with no support for video, no camera, etc., made for business.

IBM X31 / X40 – These are both ultraportables in size and weight with decent processing power. The X31 is a bit larger than the X40 but has a faster processor with something like 4 to 5 hours of available battery power. The X40, on the other hand, is smaller and lighter than the X31 but with slower processor and only 2.5 to 3 hours battery life on the standard, small battery but significantly longer, I think 6+ hours on the large battery.
Apple 12 inch Powerbook G4 – An all in one package with a fast processor, excellent graphics, great OS experience, and excellent battery life, while remaining lighter than the iBook. My current notebook of choice.


There are always a number of steps that can be taken to squeeze every ounce of power from your mobile devices, whether new or current. Being mobile quite often, I have picked up a few interesting tidbits and practices here and there to make the most of the precious battery life at my disposal:

1. Turn Those Radios Off! – Most mobile devices now come with either or both WIFI and Bluetooth built-in. Typically, users would leave either or both these features on due to ignorance of the implications of this or simply convenience of instant availability. It is important to note that keeping these radios on actually drains quite a bit of battery power as they are constantly searching for signal. A cool trick I learned from a fellow Mac user is to set different “Locations” corresponding to how I connect to different networks. For example, I have a Location for “Mobile – WLAN” that I use when I am in a WIFI hotspot, and one for “Office” which turns off WLAN but turns on my Ethernet port. Bluetooth is always off except when I intend to connect via GPRS, in which case I set my location to “Mobile – GPRS” and manually turn on Bluetooth. I actually notice the remaining uptime on the battery monitor increase or decrease depending on the mode I am in.
2. Eject Unused Peripherals – Techies know that powered peripherals without external adaptors like USB CD ROM Drives and PC Cards actually draw their power from the USB or PC Card slots themselves. While the device may not actually be in use, just keeping the device connected and powered on actually does consume power from the notebook. It is therefore a good idea to keep unnecessary peripherals disconnected, again without unduly hampering user experience. For instance, during my TabletPC days, I only connected my CD ROM drive when needed, and just for the period it was in use. On the other hand, I did have a Nokia D211 multi-mode GSM/GPRS/WIFI radio card permanently plugged into the notebook just because it was so convenient to just turn the software on and connect immediately. All in all a pretty good balance between usability versus effect on battery life.
3. Custom Configure Power Management – This is an absolutely critical step on all mobile devices and ranks as the second most important thing I do whenever I get a new or reformatted device (the most important for me being configuration of network/connectivity settings). I just noticed that default power options presented just could never just match my usage habits and battery requirements. I therefore adjust everything with careful attention to the screen (both brightness and being on or off), and for notebooks hard disk access and CPU power. As a guide, I always set my “on battery” settings such that I get minimum acceptable screen brightness (which I further adjust while using depending on ambient light), backlight shutoff of about 1 minute or less for PDA/PDA-Phones and cellphones, and screen blackout of about 3 minutes for notebooks and PDA/PDA-Phones. In addition, I set my hard disk on my notebook to turn off as often as practicable as a spinning hard drive is a real battery hog. I even had a notebook once that went as far as to allow me to set variable CPU speed, screen brightness, and hard disk speed depending on the battery level, i.e., 80% to 100% battery would allow the CPU to run at 100% speed but 20% battery power would only allow the CPU to run at 30% speed.
4. Be Battery Aware – Being a “battery aware” mobile user really means a whole lot of things:
a. Turn off unused applications – You may not notice it, but applications running in the background actually use up CPU cycles periodically. Turning off these applications, aside from making your computer a bit faster by freeing up more RAM, will reduce CPU load, which should marginally increase battery life.
b. Manage sound and vibration modes – Sound can really eat up your battery, especially when at loud volumes for ringtones and especially speakerphone mode. I normally fully configure sound for each device not just for battery purposes but also to lessen irritation from a noisy device. On a Windows PC, in particular, the startup and shutdown sounds are a large battery drain. Depending on the device, turning on vibrate mode is also a large battery drain.
c. Go to sleep – For notebooks, sleep mode offers a great way to increase battery life. Note that the startup process for a notebook is a huge battery drain because the CPU and hard disk is running at full speed. Sleep mode will avoid this while making startup time quite quick. I noticed that some platforms actually manage this better than others.
d. Avoid unnecessary multimedia usage – This is important for all devices but in particular for PDA-Phones and color cellphones. While it is tempting to watch music videos, dvds, porn, or streaming audio or video on your device, note that video and sound also significantly shorten battery life. The worst thing you can have while out of the office all day is a PDA-Phone with no battery, or what the people in Mapalad fondly call a “paperweight”.
5. Charge When You Can – No need to talk about this in great detail, but suffice it to say that batteries of today are nothing like the Ni Cd batteries of old where a full drain is necessary to avoid the “memory effect”. Charging can be done at any time, subject to what your device instruction manual says about battery calibration, periodic conditioning, or other similar items.

Power Peripherals

Regardless of how much a battery is optimized, the user will inevitably need charge the device. Since I carry quite a number of mobile devices (notebook, personal cellphone, work issued PDA-Phone, iPod) the cables and power adaptors would probably add up in weight quite significantly. To keep myself traveling light, I have tried to move as much as possible into USB based charging devices. For example, I have two Brando retractable cables in my notebook bag, one for my iPod and one for my T68i (which I use to connect the notebook via GPRS). I also have a USB to cigarette lighter adaptor in the car and a USB to AC power adaptor which I leave in my room so I can plug into my notebook while mobile, but can just plug into the car or AC if available.

On my to do list from a power management perspective is to try out these mobile power inverters that are available in the market. There are generally two flavors, one for car power and another for airplane in-seat power. The car power inverter is more relevant to me as I rarely get to sit in an airline seat with in-seat power. I heard that these inverters sometimes break the battery of the device, so I will tread carefully, but this should be an interesting proposition for the true road warrior.


One comment

  1. The Notebook is of course one of Nick Sparks best tear jearker novel. Nick is really very talented guy :””

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