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Debunking Battery Life Myths for Mobile Phones, Tablets, and Laptops

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Batteries need to be cared for properly — they’re a critical part of our mobile devices and battery technology hasn’t advanced as fast as other technologies. Unfortunately, there’s a lot of incorrect information about batteries out there.

Some of the big myths come from old battery technologies and are actively harmful when applied to new battery technologies. For example, nickel-based batteries needed to be fully discharged, while modern lithium batteries shouldn’t be fully discharged.

Perform Shallow Discharges; Avoid Frequent Full Discharges

Old NiMH and NiCd batteries had a “memory effect” and had to be completely discharged from 100% to 0% to keep their capacity. Modern devices use Lithium Ion batteries, which work differently and have no memory effect. In fact, completely discharging a Li-ion battery is bad for it. You should try to perform shallow discharges — discharge the battery to something like 40-70% before recharging it, for example. Try to never let your battery go below 20% except in rare circumstances.

If you were to discharge your battery to 50%, recharge it, and then discharge it to 50% again, that would count as a single “cycle” with modern Li-ion batteries. You don’t need to worry about performing shallow charges.

There’s only one problem that shallow discharges can cause. Laptops can get a bit confused by shallow discharges and may show you wrong estimates for how long your device’s battery will last. Laptop manufacturers recommend you perform a full discharge about once per month to help calibrate the device’s battery time estimate.

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Heat (and Cold) Can Damage Batteries

Heat can reduce a battery’s capacity. This affects all types of devices — even smartphones heat up when performing demanding tasks — but laptops can become hottest of all when under load. The battery is in the laptop, near the electronics that become hot while working heavily — this contributes to battery wear.

If you have a laptop that you use plugged in all of the time and it gets quite hot, removing the battery can increase the battery’s life by limiting the battery’s exposure to the heat of your laptop. This won’t make too much of a difference in normal use, but if you’re using a laptop to play a lot of demanding games and it’s heating up quite a bit, it may be helpful. Of course, this only applies to laptops with removable batteries.

Your climate is also a concern. If it gets very hot where you live or you store your device somewhere that gets very hot — say, a hot car left in the sun on a summer day — your battery will wear down faster. Keep your devices near room temperature and avoid storing them in very hot places, such as hot cars on summer days.

Extreme cold temperatures can decrease the lifespan of your battery, too. Don’t put a spare battery in the freezer or expose any device with a battery to similarly cold temperatures if you’re in a region with cold temperatures.

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Don’t Leave the Battery At 0%

You shouldn’t leave the battery in a fully discharged state for very long. Ideally, the battery wouldn’t discharge all the way to zero very often — but if it does, you should recharge it as soon as possible. You don’t have to race to a power outlet when your smartphone dies, but don’t throw it in your drawer and leave it there for weeks without charging it. If you let the battery discharge completely and leave your device in a closet, the battery may become incapable of holding a charge at all, dying completely.

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Store Batteries at 50% Charge

On the other hand, leaving the battery charged fully for an extended period of time could result in a loss of capacity and shorten its life. Ideally, you’d store the battery at 50% charge if you weren’t going to use it for a while. Apple recommends you leave the battery at 50% if you intend on storing the device more than six months. If you’re using it regularly, you shouldn’t need to worry about its state — although you never want to leave a battery at 0% for too long.

Storing the battery while fully discharged could result in the battery dying completely, while storing the battery at full charge could result in the loss of some battery capacity and shorten your battery’s life.

This applies to both batteries in devices and spare batteries you may have lying around — keep them at 50% if you won’t be using them for some time.

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Leaving Your Laptop Plugged in All The Time Is Okay, But…

This one appears to be fairly controversial. We’ve previously covered the eternal question of whether it’s okay to leave your laptop plugged in all the time. We concluded that it’s okay and the battery’s temperature is the main thing you need to worry about. Apple disagrees, recommending against leaving its Macbook Air and Macbook Pro notebooks plugged in all the time.

Ultimately, we’re both saying the same thing. It’s fine to leave your laptop plugged in at your desk when you’re using it, as the laptop won’t “overcharge” the battery — it will stop charging when it reaches capacity. However, just as you shouldn’t store your laptop’s battery at full capacity in a closet, you shouldn’t leave your laptop plugged in for months on end with the battery at full capacity. Allow your laptop’s battery to occasionally discharge somewhat before charging it back up — that will keep the electrons flowing and keep the battery from losing capacity.

Battery University says that “the worst situation is keeping a fully charged battery at elevated temperatures.” If your laptop produces a lot of heat, removing it might be a good idea. If you have a fairly cool laptop that you occasionally let discharge a reasonable amount, leaving it plugged in — even for days on end — shouldn’t be a problem. If your laptop gets extremely hot, you may want to remove the battery, as we mentioned above.

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Batteries Will Always Wear Down

Like all other types of batteries, Li-ion batteries will wear down over time, holding less and less charge. Apple says its laptop batteries will reach 80% of their original capacity after “up to” 1000 full discharge cycles. Other manufacturers commonly rate their batteries 300 to 500 cycles.

The batteries can still be used after this point, but they’ll hold less electricity and will power your devices for shorter and shorter periods of time. They’ll continue losing capacity the more you use them. Heat and aging will reduce the battery’s life, too.

Whatever you do, your devices’ batteries will slowly wear down over time. With proper care, you can make them hold a long charge for longer — but there’s no stopping entropy. Hopefully, your device will be due for an upgrade by the time its battery dies.

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For more tips on increasing your battery life, read our complete guide to maximizing your Android phone’s battery life, instructions to finding the root cause of your Android battery problems, tips for maximizing your iPad, iPhone, or iPod Touch’s battery life, and introduction to using the Windows power troubleshooter to increase battery life.

Image Credit: John Seb Barber on Flickr

Chris Hoffman is a technology writer and all-around computer geek. He's as at home using the Linux terminal as he is digging into the Windows registry. Connect with him on Google+.

  • Published 08/6/13

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