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.
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.
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.
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.
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.