How to Charge and Care for Your Mobile Device Battery

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Rechargeable batteries that use nickel-cadmium (NiCad) and nickel-metal hydride (NiMHi) are known to have a “memory effect.” If you don't “teach” your rechargeable batteries their full potential by cycling them from completely full to completely empty, they'll “forget” how much energy they can store. But that’s not true for batteries that use lithium-ion, like the ones used in portable computers, tablets, and phones.

Below is a quick guide to ensuring long service life, maximum charge per day, and safe storage of any device that uses a lithium-ion battery.

Charge frequently.

To get the most out of a lithium-ion battery, you should try to keep it between 40% and 80% capacity as often as possible. Generally speaking, completely draining and charging won’t help. In fact, it will reduce the lifespan of the battery over time.

Don’t keep your devices charging all the time.

Lithium-ion batteries can overheat. Fortunately, battery chargers (and device electronics) are smart enough to monitor the battery capacity and will stop charging once the battery charge is full. To keep their capacity to hold a long charge, it’s best to unplug once a battery is fully charged, and let it get some use before recharging again.

In a perfect world, you would charge to about 90%, and use the device until it reaches a 40-50% charge. Then recharge and repeat. It’s better to charge more frequently in this manner than to go from 100% down to 10% and back up again less frequently.

The next danger you’ll face is heat.

Lithium-ion batteries will degrade much faster when they’re hot, regardless of whether they’re being used or not.

At an average temperature of 32°F, a lithium-ion battery will lose about 5-6% of its maximum capacity per year. At 77°F that number jumps to about 20%. And at 104°F it skyrockets to over 30% per year. I’m not suggesting that you keep your phone in the refrigerator, but knowing how important it is to keep your device cool should help as a reminder to keep your phone out of a hot car, or your tablet out of direct sunlight.

Speaking of heat, wireless (inductive) chargers create more heat than a traditional charger and cable combination. So try to avoid using them if possible.

Store your device with a good charge.

Lithium-ion batteries degrade rapidly when they have no charge. In fact, over time they can become unstable. They can even inflate in size and rupture. Charging them can then become dangerous. Manufacturers usually include circuitry that detects this state and permanently disables the battery. Even when your device tells you it has no power left and shuts itself off, it actually does still have power, and that’s to avoid damage to the battery. Fortunately, lithium-ion batteries don’t lose power very quickly when not being used. They will generally lose 5-10% of their charge each month, provided they are completely powered off and not in standby mode. A good rule of thumb is to charge the battery to 50%-80% prior to storing it, powered off, for extended periods.

A typical lithium-ion battery lasts 3-5 years.

This means that the charge capacity is high enough that you can effectively use your device during that time period. But once you notice battery life waning, it’s time to replace the battery. Many manufacturers provide walk-in or mail-in service for a reasonable fee.

And for batteries that you must discard or replace yourself, I highly recommend that you take the old battery to your local Lowe’s, Radio Shack, or other location that accepts old batteries and recycles them. It’s the right thing to do, and is safer than shoving it in a drawer or having it end up in a landfill.

Michael directs all design initiatives, heads marketing, and builds cool software for Fynydd. He's also a husband, father, avid reader, advocate for reason and science, and autodidact.

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