Lithium-ion batteries have been in the news lately for causing fires and explosions. Explosions have happened with e-cigarettes, hoverboards, and the Samsung Galaxy Note 7, which was banned from all flights by the FAA due to its explosion risk. Despite the risks, most of today’s most popular gadgets have a battery.
Fred Langa at Windows Secrets Newsletter posted an article on how to get the most out of the lithium-ion (Li-ion) batteries. Li-ion batteries need very different care and feeding than the nickel-cadmium (Ni-Cd) and nickel-metal-hydride (Ni-MH) batteries used in earlier devices. Proper care of a Li-ion battery can result in as much as 15 times longer service life than with an improperly cared-for battery.
Steps to extend the battery service life
The article does not cover ways to get more run time between recharges; those techniques are already well-known. Most portable devices offer ample manual and automatic power-saving modes and methods such as adjusting screen brightness, slowing CPU speed, and reducing the number of apps running.
Rather, the article focused on ways to extend the battery’s overall service life. Follow these five important tips, and you’ll help make sure that your Li-ion batteries will deliver long, full, safe service lives in your new portable devices.
Keep your lithium batteries cool
Heat is the number-one enemy of Li-ion batteries. Heat issues can be caused by usage factors such as the speed and duration of battery charging and discharging. The physical environment also matters. Simply leaving your Li-ion powered device in the sun or in an enclosed car, even if the device isn’t being used, can significantly reduce the battery’s ability to take and hold a charge according to the article.
Li-ion batteries perform best at about normal room temperature (68F/20C). If the device warms to 86F/30C, its ability to hold a charge drops by about 20%. Mr. Langa says if the battery is used at 113F/45C — a temperature easily reached by devices that are working hard or that are in the sun, battery capacity can be reduced by 50%.
So if your device or battery becomes noticeably warm while you’re using it, the article recommends moving to a cooler place. If that’s not possible, try reducing the amount of power the device is using by turning off unneeded apps, reducing screen brightness, or activating the device’s power-saving mode.
Of course, you can turn the device fully off until its temperature returns to normal. For fastest cooling, remove the battery, if possible Windows Secrets recommends. The battery and the device will cool off faster if they’re physically separated according to the article.
Low temperatures aren’t as much of a worry. Low temps usually won’t cause any long-term damage, although a cold battery won’t produce as much power as it otherwise would. The power drop becomes very noticeable at temperatures lower than about 40F/4C. Most consumer-grade Li-ion batteries are essentially useless at temperatures below freezing.
If your Li-ion powered device becomes excessively chilled for any reason, don’t try to use it. The article says to leave it powered off and move it to a warm place until the device is at normal temperature. Once the battery warms to a normal temperature, so will its electrical performance.
Unplug the charger
Overcharging, leaving a battery connected to a too-
high voltage source for too long, can reduce a Li-ion battery’s ability to hold a charge, shorten its life, or kill it outright according to the author. Most consumer-grade Li-ion batteries are designed to work at around 3.6 volts per cell but will accept a temporary overvoltage of around 4.2 volts while charging. Mr. Langa warns that if a charger outputs the higher voltage for too long, internal battery damage can occur.
In severe cases, Windows Secrets warns that overcharging can lead to what battery engineers delicately refer to as “catastrophic failure.” Even in moderate instances, the excess heat produced by overcharging will negatively affect battery life, as you saw in Tip #1.
High-quality chargers can work in concert with circuitry inside well-designed Li-ion-powered devices and their batteries, reducing the danger of overcharging by properly tapering off the charging current. The article says the simplest, can’t fail method is not to leave your Li-ion devices connected to any charger longer than needed.
These properties are quite different from those of older Ni-Cd and Ni-MH battery technologies, which did best when left on their chargers for as long as possible. That’s because those older battery types have a high rate of self-discharge; that is, they start losing a significant amount of stored energy the moment you take them off the charger, even if the device they power is turned off.
In fact, a Ni-Cd battery can self-discharge at a rate of 10% in the first 24 hours. The self-discharge curve flattens after that, but a Ni-Cd battery will still lose an additional 10–20% charge per month. Ni-MH batteries are even worse. Their self-discharge rate is about 30% higher than that of Ni-Cd.
But Li-ion batteries have a very low rate of self-discharge. A healthy, full, lithium battery will self-discharge at about only 5% in the first 24 hours off the charger — with only 2% or so per month after that.
It’s simply not necessary to leave a Li-ion device on the charger until the last possible moment. For best results and the longest battery life, unplug the charger when it or the lithium-powered device shows a full charge.
It’s also not necessary to give new Li-ion devices an extended charge before first use. (Ni-Cd or Ni-MH devices used to come with warnings to do an initial charge of anywhere from 8 to 24 hours.) Li-ion batteries are fully ready for use when the charger or the device reads 100% charge. No extended charging is needed.
Don’t deep-discharge your battery
Not all discharge cycles exact the same toll on a battery. Long and heavy usage generates more heat, putting more stress on the battery; smaller, more frequent discharges extend the overall life of lithium batteries.
You might think that a higher number of small discharge/recharge cycles would eat into the battery’s overall lifespan. That was true with older technologies, the author says it’s not the case with Li-ion. Battery specs can be confusing because most manufacturers count a full Li-ion charge cycle as whatever it takes to add up to a 100% charge. For example, three 33% discharge/recharge cycles equal one full-charge cycle, five 20% cycles equal a full charge, and so on.
In short, a higher number of small discharge/recharge cycles doesn’t reduce a lithium battery’s total available full-charge cycles.
Again, heat and stress from heavy discharges cut battery life. So try to keep your deep-discharge events to a minimum. Mr. Langa recommends that you don’t let your device routinely run down to zero charge (where the device turns itself off). Instead, think of the bottom 15–20% of battery capacity as a reserve — for emergency use only. Get into the habit of swapping in a fresh battery (if possible) or plugging the device into external power well before the battery is empty.
Slow and steady is best
As you now know, both fast discharging and fast recharging generate excess heat and exact a toll on battery life. Windows Secrets says if you’ve run a device long and hard, let the battery cool to room temperature before recharging it. Batteries won’t accept a full charge when hot. And when recharging, make sure your charger doesn’t make the battery become hot to the touch, a hot battery is a sign the charger is pumping too much current, too fast, through the battery.
Overcharging is more likely with chargers that are cheap, off-brand models; that use fast-charge circuitry; or that are wireless (inductive). These “dumb” chargers simply pump out current, accepting little or no feedback from the device being charged. Overheating and overvoltages can easily occur, damaging or even destroying the battery.
Fast chargers provide a useful charge to a drained battery in minutes and not hours. The author explains there are various approaches to fast-charging technology, and not all of them are compatible with all lithium batteries. Unless the charger and the lithium battery are specifically designed to work together, fast charging could cause overheating and overvoltages. Generally, it’s best not to use one brand of fast charger on a different brand’s device.
Wireless (inductive) chargers use a special charging mat or surface to restore a battery’s power. It sounds wonderfully convenient, but inductive charging always generates excess heat, even when it’s working normally.
Not only is the excessive heat produced by a wireless charger not good for lithium batteries, it also wastes energy. By its nature, inductive charging’s efficiency is always going to be lower than a standard charger’s. Mr. Lunga says that higher heat and less efficiency easily outweigh convenience.
In any case, the safest approach is to use only chargers sold by the OEM of your lithium-powered device. It’s the only way to be sure that the charger will keep temperatures and voltages within specs. The article recommends that if a OEM charger isn’t available, use a low-output charger that’s unlikely to pump damaging amounts of power into the device you’re charging.
One source of low-output, non-OEM charging that’s often available is the USB port on a standard PC. A typical USB 2.0 port provides 500mA (.5 amps) per port; USB 3.0 provides up to 900mA (.9 amps) per port. In contrast, some dedicated chargers will output 3,000-4,000mA (3-4 amps). The low amperage offered by USB ports will usually provide cool, safe charging of almost any Li-ion device.
If possible, carry a spare battery
If your device allows for easy battery replacement, carrying a spare battery is cheap insurance. It will give you twice the run time. When the in-use battery approaches 15–20% charge, simply swap out the drained battery for a fresh, cool one — you get instant full power, with no heat worries.
A spare battery also allows for other benefits. For example, if you find yourself in a situation where the installed battery is running hot, you can swap out the hot battery to let it cool. Having two batteries should also eliminate any need to use fast chargers — you can charge the spare at a safe, slow rate while the other is in use.
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For more tips on how to keep your Apple iPhone battery in tip-top shape, check out this post from 2014.
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Ralph Bach has been in IT long enough to know better and has blogged from his Bach Seat about IT, careers, and anything else that catches his attention since 2005. You can follow him on LinkedIn, Facebook, and Twitter. Email the Bach Seat here.
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The peacock effect – We might want to impress a possible partner with our fancy phones. The researchers compared the phenomenon to “displays of affluence by wearing designer fashion clothes or jewelry … to enhance or affirm a person’s social standing and to attract a suitable mate.”
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