With a smartphone in every person’s pocket these days, the reliability of a device’s battery is crucial.
Due to the restrictions of early cellphone batteries, owners were advised to let the battery drain completely before charging it again – along with other safety and reliability tips.
While the lithium-ion batteries used in modern smartphones are far more reliable than their predecessors, users worry that their charging habits are hurting battery capacity.
The answer as to how to correctly charge and maintain a lithium-ion battery has received many answers from experts over the years – several of them conflicting at a fundamental level.
We examined evidence and expert opinions to determine if any of these “charging myths” have merit.
Charging to 100%
Speaking to The Verge, Princeton associate professor Daniel Steingart said the easiest thing to do is to “just keep the device plugged in all the time, or as much as you can.”
A smartphone’s software will recognise when its battery is charged and will stop charging the device.
This means you technically can’t overcharge your device, and it should be fine to charge it to 100%, or leave it on overnight.
ACCESS director Venkat Srinivasan refuted Steingart’s assertion, however, saying that you should never charge your battery to 100%.
“Get it up to 90%, and then stop it,” he said.
Srinivasan said users should keep their batteries between 30-80%, as once they reach 100%, certain reactions can occur which degrade electrolytes and decrease battery capacity.
Steingart agreed that this process occurs, but said keeping your device at 100% does not worsen the severity of these reactions.
This means that once you charge your device to 100%, you can keep it fully charged as long as you like. Keeping your device in the 30-80% battery range could increase its lifespan, though.
Samsung has said charging your device overnight is not a good idea, and that leaving your phone connected to a charger when it is fully charged could lower battery life.
“Technically, you should not be charging your phone for extended spans of time – so overnight phone charging is a big no,” it said.
“Avoid charging it to 100% and then leaving it connected to a charger.”
It agreed with Srinivasan’s assertion that Lithium-Ion batteries perform better if you do not charge them to 100%.
Overcharging a lithium-ion battery can cause a plating of metallic lithium to form on the cells, compromising safety.
According to Battery University, most lithium-ion batteries used in smartphones are of the cobalt-blended variety, which means they are vulnerable to this stress.
Device manufacturers account for this, however, by stopping the flow of current into the battery when it is fully charged.
Battery University recommends turning off your device when charging it for an extended amount of time, although the amount of stress placed on your device by a continuous charge would depend on your device’s charging control hardware.
Fully depleting your battery before charging it in order to train it is an old myth, according to Galeas Consulting president Bruno Scap.
Scap said that certain batteries may even disable themselves as a safety mechanism if they are discharged too much.
In fact, lithium-ion batteries function at their best when above a 50% charge, as repeatedly draining the battery may shorten its lifespan and decrease overall capacity.
Samsung advised users to keep their battery above 50%, agreeing that draining the device many times could shorten its lifespan.
“One full drain a month is allowed for calibration purposes, but anything more than this will shorten your battery’s lifespan.”
It is important to note that the durability and capacity decay of the lithium-ion batteries used in smartphones are measured in cycles, which consist of full 0-100% discharges and recharges.
If you want your battery to last as many cycles as it can before it degrades, experts recommend constantly keeping the device above 50%, but below 80%, turning it off when charging, and never allowing it to deplete fully or to become fully charged.
The increased lifespan gained by following these tips has not been measured, however, and may not be significant in many cases.