how bad is it to overcharge your cellphone?

It’s an issue that has plagued humanity since the dawn of the mobile phone. We use our trusty pocket computers so much that they rarely get through a day with any power left. Many of us plug them in at night and fall asleep, content in the knowledge that we’ll wake up to a fully charged device.

But is it really safe to leave our phones plugged into the charger once they’re fully charged? Is it damaging the battery — or shortening its lifespan?

There are lots of myths and questionable ideas on this topic. You’ll find the Internet awash with opinions masquerading as facts. What’s the truth? We’ve got some answers for you.

Should you leave your phone plugged into the charger overnight?

“Leaving your phone plugged in overnight is okay to do, it will not drastically harm your device,” says Shane Broesky, co-founder of Farbe Technic, a company that makes charging accessories. “Your phone is very smart. Once it’s fully charged, it knows when to stop the current from coming in to protect your phone from overcharging.”

So far so good, but there are situations when leaving that smartphone plugged in overnight can slowly reduce the lifespan of your battery.

“Lithium-ion batteries can react poorly if your phone experiences elevated temperatures, leading to a damaging effect,” explains Shane. “If you have a case on your device that does not allow heat to escape, this heat will increase the temperature of the battery and will cause cell oxidation, which will shrink the capacity and shorten the lifespan.”

Make sure you take your phone case off at night if you’re going to leave your phone plugged in and charging, in other words.

What’s the optimum way to charge your phone?

“The sweet spot for lithium-ion batteries is to keep them charged between 50 and 80 percent. This allows for the charged ions to continue to work and protect the life of your battery,” says Shane. “Charging your device in short spurts throughout the day will give these ions just enough energy to keep them going.”

So frequent top-ups, rather than one daily charge up, is healthier for your battery. It’s not convenient, but that’s the optimal way to charge your smartphone if you want to ensure the longest life possible.

What to avoid

“The major threat to your battery is charge cycles,” Shane explains. “A charge cycle is where your battery goes from empty or near-empty to full — and every phone battery has a limited number of charge cycles before the end of its life.”

You may have a high number of charge cycles before that limit is reached, but eventually the battery is going to noticeably degrade. When it does, you’ll find that it lasts only a very short amount of time, or it will simply not turn on at all.

what some specialists say.
M.E energy storage.

If you have a smartphone produced by a reputable mfr, then the on-board BMS will prevent your battery from over-charged. If I have to charge my phone after its battery is 50% or more depleted, then I put a pen under the phone to provide more space for convective air cooling. If you’re a purest or extremist in maximizing the battery’s life, then you can put an aluminum plate the size of the cell phone or larger under the phone when charging to conduct heat away faster.

Whenever a Li-ion (mainly LCO types or 3.7V nom.) battery is charged, the internal ion exchange heats up chemicals within the cell from internal resistance. The higher the rise in temperature, the greater degradation occurs to the chemistry. The longer the cell experiences the heat, the degradation extends further.

So, to maximize life for a Li-ion battery:

Charge it as often as possible to minimize its depth of discharge (DOD). For example if a battery has been discharged 1/4 of its capacity, then that’s 25% DOD. If 3/4 of its energy has been discharged, then that’s 75% DOD. The longer a battery is being charged, the more heat build-up occurs.

If you have to charge it for more than 5-minutes, then don’t put the phone on a pillow, on a blanket or on any soft surfaces that can insulate the heat from escaping. Put the phone on a metal surface, on a laptop cooling pad with fans or any place with a cool air current to remove the heat generated from charging. Crushed ice with water in a zip-loc bag can help in cases of extremely over-heated mobile phones. Never charge Li-ion batteries when it is below 0°C or 32°F. So, remove the ice pack as soon as the cell phone is back to room temperature.

technology and investment expert

It’s not that bad at all.

The battery itself relies on a redox reaction between two substances. The reaction is constantly trying to maintain equilibrium - when you discharge the battery, the (spontaneous) reaction is moving forward, while when you are charging the reaction is moving the opposite way. Think of it as a set of scales, with both weights constantly battling each other.

When you overcharge your phone, you are just moving the reaction even more, but it reaches a final point, so you can’t really overcharge your phone at all. The degradation of the reaction will often surpass any damage caused by overcharging anyway.

To keep your battery healthy, you can do a “battery cycle”. This re-calibrates the battery sensor on the phone. Simply use your phone until it dies, and then charge it to 100%.