The Best Way to Charge Your Electronic Devices
Isn’t it annoying that you have to buy a new phone just because of a dead battery while your device still works smoothly? There are different tales telling you how to optimise battery life. An old-fashion rumour says you should fully charge your portable devices at low battery. Another claims that Li-batteries are now designed to be smarter than before, so just charge your phone whenever you can. Which statement is correct then?
Why does your battery go flat faster?
It’s too normal to find a phone’s battery drops faster than a brand-new one when you have used it for a couple of years. This is because the electricity carrier, Li ions, moves back and forward between the cathode and the anode when the battery is used and charged. Over time, more and more Li ions permanently ‘migrate to’ the anode so the cathode has less Li, which results in a loss in capacity. Generally, manufacturers claim that a lithium-ion battery can undergo 300-500 cycles of discharge and recharge. The actual number of cycles does depend on your charging habit. For example, the temperature under which you charge your phone, and at what percentage you plug it in.
Low battery by Helen Lin (Helen’s own private collection)
What’s the best charging strategy?
A group of researchers give a straightforward answer by their experiment. As demonstrated in Figure 1, charging a phone at 65% battery and stopping, not when the battery is fully charged, but at 75%, results in the longest battery life. Obviously, nobody can regularly charge electronic devices in this way. So a simple but practical tip is: charge your phone often, earlier before the low-battery alert pops up. It’s also better to avoid hot or cold charging condition and do it under normal room temperature.
Figure 1. Capacity loss given different charge and discharge ranges. (Bolun Xu et al, 2016)
Should you unplug your charger as soon as the device is charged?
Don’t worry. Your laptop will not be harmed if it’s kept plugged in, no matter you are using it or not. The power system will automatically stop charging when the battery is full. The device can protect itself from overcharge so you don’t have to do anything. Also, modern chargers consume omittable amount of energy when they are plugged in. You won’t observe any change on your bill even though you manage to disconnect them as soon as the devices are fully charged.
Should I keep my laptop plugged in to conserve the battery?
Your laptop will switch to AC supply from DC when it’s connected to a power point. Since it is off-duty, the battery can rest after it is recharged. Keeping plugged in seems to be a way to protect the battery. However, occasional use of DC supply is necessary because it keeps electrons active so the battery maintains a ready-to-use condition.
An analogy can perfectly explain why you should neither drain the battery nor avoid using it at all. A person needs some exercise to keep fit. Ordinary people don’t train as harsh as professional athletes, who may otherwise get injured when they have excessive workout. Rather, if you don’t exercise at all, your muscle will certainly lose its strength. Likewise, a battery will not do its job if it hasn’t been used for too long.
Now you can see, to prolong battery life follows a similar rule to maintaining good health: don’t leave it to starve, and make sure it has moderate exercise!
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