Get The Most From Your Laptop Battery – Maximizing Runtime and Service Life – The ‘Book Mystique

The ability to operate under battery power is both the raison d’etre and the Achilles’ heel of portable computers. In theory, battery powered computing is ideal. You can slip the surly bonds of cords and cables and compute freely wherever you please, and with WiFi even surf the Web if you’re within range of a connected wireless router.

The snake in this garden of portable computing delights is the limited duration of battery charge life. This aspect of portable computing is of course better than ever with today’s portables — especially MacBook Airs and iPads than it was in the early days of Mac portable computing. I recall a PowerBook 165c belonging to a friend of mine that could barely squeeze out an hour’s use on a charge of its nickel cadmium (NiCad) battery.

Things improved markedly with the Nickel Metal Hydride (NiMH) cells introduced with Apple’s 500 series PowerBooks and ‘040 Duos in 1994, and carried over in the 5300/190 and 1400 series. I found that I could manage about one and one-half to two hours of the sort of computing I do on battery power with my grayscale 5300.

Battery charge life was extended again with the arrival of Lithium Ion (LiIon) batteries that finally shipped with the PowerBook 3400 Series in 1997. The PowerBook 5300 was originally supposed to have Lithium Ion batteries, but it was one of the Sony LiIon units that caused the legendary and infamous 5300 spontaneous combustion in an Apple test lab that resulted in an across-the-board substitution of the NiMH battery originally intended for the low-end 190 series only.

The Lithium Ion cells improved battery life somewhat over the performance of the NiMH batteries, although I didn’t personally note a dramatic increase in actual charge duration with my 1998 WallStreet 233 MHz com to the 5300, presumably because the faster G3 processor and larger color screen of the WallStreet drew enough extra power to largely negate the Lithium Ion cells’ nominally longer charge life. I could usually get about two hours computing at the outside with the WallStreet on battery power.

The next and most recent battery revolution for Mac portables came with the March 2009 17” unibody MacBook Pro release, followed by a second revision 15” MacBook Pro and newly designated full Pro status 13” models, all featuring Apple’s new lithium polymer built-in, non removable (without a teardown) batteries claimed to provide up 40 percent longer runtime — up to 10 hours on the 13-inch MacBook Pro and 8 to 9 hours on the 15- and 17-inch models).

Apple’s theory was that by eliminating all the parts required for a removable battery and embedding the battery into the notebook, it would create enough space for a battery with significantly greater capacity. The downside of course is that once the battery is discharged, you’re out of business until you find an external power source to plug in and recharge.

The MacBook Pro lithium polymer battery innovations extend beyond physical configuration, and into the chemical makeup of the battery. Battery lifespan is measured in recharges. One recharge is a complete charge and discharge of a battery’s energy. A recharge doesn’t necessarily occur every time you plug in your notebook; many partial charges can add up to a single full recharge. Thanks to their aforementioned advanced chemistry and Adaptive Charging, the built-pin MacBook their original capacity — nearly three times the lifespan of typical notebook batteries.

Normally, the battery recharges automatically when you have its AC power adapter plugged in, charging fastest when the ‘Book is shut down or sleeping, less rapidly if it is in use. PowerBook and early generation MacBook Pro and MacBook lithium ion batteries were designed to last through about 500 charges, but it was futile counting, as there are too many other variables that affect battery service life, making the “500 charges” figure no more than a very loose ballpark estimate. Eventually, the battery will just refuse to hold a charge for useful amount of time, at which point you will need to purchase a replacement. Easy with removable batteries, and if you had two more you could multiply your computing time between charges when you’re away from AC power by how many-x charged units were available.

The main difference between lithium ion and Lithium polymer batteries is that the latter use a solid, ion-conductive, polymer material rather than the liquid electrolyte used in standard Li-ion batteries, although most polymer batteries also contain an electrolyte paste to lower the internal cell resistance. Eliminating the liquid electrolyte allows the polymer battery to be housed in a foil pouch rather than the heavy metal case required for LiIon batteries, which in turn makes non-standard and irregular battery form factors possible, for example allowing Apple to design its built-in notebook battery packs with shapes that can fit into more nooks and crannies of the computers enclosure that would otherwise be occupied by empty space, thus increasing battery capacity without enlarging the computer. Lithium polymer batteries are also cheaper to manufacture than lithium-ion units.

The Energy Saver Preference panel in OS X is provides an avenue of battery conservation defence, offering respective modes for Battery and Power Adapter, switching automatically between them when you unplug/plug in your laptop. You can thus configure the Power Adapter mode for prodigal energy consumption, while setting the Battery mode for power parsimoniousness. The Energy Saver Preference panel enables you to specify intervals between monitor backlight dimming, automatic sleep and wake up, and so on.

Personally, I keep my laptops plugged in 24/7/365 except for when I am on a road trip or doing some portable computing around the house, although this is probably not the ideal strategy for optimizing battery life, it seems to have worked well for the me. A I’ve been using Apple laptops almost exclusively since 1996, and the only ones I’ve ever being obliged to replace the batteries in are my Pismos, but they’ve been in costs and service for going on 10 years. Of course, the original batteries in my PowerBook 5300 and PowerBook 1400 have long since expired, but those machines are not in service anymore. The oldest battery we currently have in active service is the original one in the PowerBook G4 17 inch, which was Apple Certified Refurbished in 2005. It’s of course not 100% anymore, but it still has enough life to do a bit of portable computing after having been essentially plugged in 99 point something percent of the time since I bought it in February, 2006.

What I find really interesting is that while keeping a lithium-ion battery constantly under full charge and in a relatively warm environment ( IE: inside the laptop), after 25 months of that, http://www.coconut-flavour.com/coconutbattery/ CoconutBattery informs me that the original battery in my aluminum unibody MacBook actually still has in excess of 100 percent of its original 4100 mAh charge capacity. however, that’s an observation, not a prescription.

As I understand it, ased on research, it’s not recommended in the interest of longevity to to either maintain a LiIon battery indefinitely in fully charged condition or to run it completely dead or lower than 20 percent retained charge very often. The book on ideal sort of usage for getting long life out of a LiIon battery is to use it frequently, but for relatively shallow discharges of only 20% or 30% of battery charge capacity before recharging, which is said to extend cycle life considerably.

It’s notable that new plug-in hybrid and full electric cars with lithium-ion batteries like the Chevy Volt and Nissan Leaf, for the sake of battery durability, limit system access to only about 65 percent of the “middle” of the battery pack’s charge capacity, leaving large buffer reserves that can only be dipped into for short bursts, like hard acceleration.

As a general rule, for lithium ion batteries, five to 10 shallow discharge cycles can be considered roughly equal to one full discharge cycle., and partial-discharge cycles can number in the thousands over the course of a battery’s useful life. That’s the sort of discharge cycle my laptops usually get when they are called on to run off battery power, but I can’t really say that I’m following the guidance, since my machines (except for my “road” laptop, which is currently a Pismo) often stay plugged in, on charge, battery in place, for literally months at a time without being subjected to a discharge.

Lithium-Ion and lithium polymer batteries are also memory-free in terms of performance deterioration, short discharges with subsequent recharges do not provide the periodic calibration the battery’s state-of-charge time gauge. A deliberate full discharge and recharge every 30 charges corrects this problem. Letting the battery run down to the cut-off point in the equipment will do this. While most laptop manufacturers, including Apple, recommend discharging and recharging the battery about once a month to recalibrate the battery, the that seems too counter-intuitive to me given the contradictory advice to avoid deep discharges, with shallow discharges being the ideal, and I almost never do it.

It is also suggested that laptop battery service life can be extended by removing the battery from the laptop and storing it at about a 40% state-of-charge in a cool but not freezing cold environment (i.e.: the refrigerator but not the freezer). I don’t doubt the theoretical veracity of that, but it would negate one of the marquee reasons that I use laptops by preference in the first place, to wit: that I can cruise through power outages, which are frequent in this neck of the woods, without data loss or even the necessity to pause what I’m doing when the power goes out. At least if I don’t need high-speed Internet, since my wireless router and the ISP tower both go down when the wall current goes away. Dial-up Internet has always worked fine here logging on with battery powered laptops through power outages, and if its a lengthy one I can recharge the laptop (or just run it) from a car battery or 12 volt power pack through an automotive adapter.

Incidentally, while cool storage is said to be ideal, something I have not experimented with myself, be very cautious about storing laptop batteries in the refrigerator. A reader reports that he tried this and ruined a battery due to moisture damage from condensation.

The most comprehensive resource I’ve found on battery care and maintenance is “Batteries in a Portable World” also by Isidor Buchmann, which is book length, so it may be a bit too comprehensive for some, but it contains a ton of useful information on batteries:
http://www.buchmann.ca/

Snippets:

”The Li-ion does not like prolonged storage. Irreversible capacity loss occurs after 6 to 12 months, especially if the battery is stored at full charge and at warm temperatures. It is often necessary to keep a battery fully charged as in the case of emergency response, public safety and defence. Running a laptop (or other portable device) continuously on an external power source with the battery engaged will have the same effect….

“The combination of a full charge condition and high temperature cannot always be avoided. Such is the case when keeping a spare battery in the car for a mobile phone. The NiMH and Li-ion chemistries are most severely affected by hot storage and operation. Among the Li-ion family, the cobalt has an advantage over the manganese (spinel) in terms of storage at elevated temperatures.

“The charge time of all Li-ion batteries, when charged at a 1C initial current, is about 3 hours. The battery remains cool during charge. Full charge is attained after the voltage has reached the upper voltage threshold and the current has dropped and levelled off at about 3 percent of the nominal charge current.

“The charge process of a Li-Polymer is similar to that of the Li-ion. Li-Polymer uses dry electrolyte and takes 3 to 5 hours to charge. Li-ion polymer with gelled electrolyte, on the other hand, is almost identical to that of Li-ion. In fact, the same charge algorithm can be applied. With most chargers, the user does not need to know whether the battery being charged is Li-ion or Li-ion polymer.”

For monitoring your batteries condition and charge status, the little freeware utility, coconutBattery, which I mentioned above, reads and displays battery data and provides live feedback of what’s going on with the battery rather than just a snapshot readout. coconutBattery features:

Current charge:
The current battery charge (in mAh – miliampere-hour)

Maximum charge:
The maximum capacity your battery can be charged with (in mAh – miliampere-hour)

Current capacity:
see ->”Maximum charge”

Design capacity:
The capacity your battery could be charged with when it leaved the factory (in mAh – miliampere-hour)

Mac model:
The Apple model identification string for your Mac

Age of your Mac
Calculates the age of your Mac using the coded production date in the serial number of your Mac

Battery loadcycles
How often was your battery loaded from 0% to 100%? (Apple battery information page)

Battery temperature:
Well, this is the current temperature inside your battery

Battery power usage
Using the MacOS internal power information, coconutBattery calculates the current power consumption of your MacBook

coconutBattery is a useful tool to have, and since it’s a tiny download and free, there’s not really any reason not to. You can download it here:
http://www.coconut-flavour.coconut battery

System requirements:
Mac OS X 10.4 or higher

coconutBattery is freeware

For more information, visit:
http://www.coconut-flavour.com/coconutbattery/index.html

There are a variety of sources for replacementApple laptop batteries. Ones I have used with excellent results include Other World Computing and FastMac. For more information, visit:
http://eshop.macsales.com/shop/powerbook/batteries/
and
http://fastmac.com/laptop.php

You can check out Apple’s battery tips at:
http://support.apple.com/kb/HT2424?viewlocale=en_US

The ‘Book Mystique archive:
http://www.pbcentral.com/columns/hildreth_moore/index.shtml