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?

Charging by Colin Harris  ADE  (CC BY-NC-ND 2.0)

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.

Electrification by Linda on the bridge to NewWhere (CC BY-NC-ND 2.0)


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!


Further readings for your interest:

Battery University – What causes a Li-ion battery to die?

Battery University – How to prolong battery life

Battery University – How to maximise battery runtime

Xu, B., Oudalov, A., Ulbig, A., Andersson, G., & Kirschen, D. S. (2016). Modeling of lithium-ion battery degradation for cell life assessment. IEEE Transactions on Smart Grid, 9(2), 1131-1140.


22 Responses to “The Best Way to Charge Your Electronic Devices”

  1. Weiyu Lin says:

    I’m glad this post interests you! Unfortunately I have no idea if there is an emerging substitute for Li batteries. I feel like there have been many technology improvements in Li batteries and energy effeciency of OS, but as far as I know, there’s not yet an alternative to Li batteries. Let me know if you encounter any fantastic news about this. It’s such a interesting topic!

  2. Weiyu Lin says:

    Thank you! Happy to know that my post helps people who are looking for these tips that I was looking for.

  3. Weiyu Lin says:

    Yeah I found it a bit hard to understand the chemistry behind this when I read the articles. I’m sorry that I didn’t make it clear in the post. Basically it’s a natural phenomenon that the chemicals decay over time so that the amount of effective ‘electricity carriers’ reduces, which results in capacity drop of a battery.

  4. Weiyu Lin says:

    Unfortunately I’m not a tech savvy person and I can’t tell how that particular program works. This is actually the first time I hear about such one. I guess programs like that may calculate and adjust charging rate (basically by controling voltage) to ensure that the phone is charged in time. Thank you for sharing this!

  5. Weiyu Lin says:

    Thanks! Hope you find them helpful!

  6. Weiyu Lin says:

    Thank you! I’m glad you like it!

  7. Weiyu Lin says:

    I’m glad that you find it useful! Hopefully tech can always dismiss our worries instead of adding confusion.

  8. Weiyu Lin says:

    To be honest I don’t completely understand why electrons or ions become less mobile if the battery is not used for a long time. All I tried to say with that analogy was that the activity of ions would decay if they were not forced to move by charging or discharing. Sorry that it confused you.

  9. Weiyu Lin says:

    Thanks mate!

  10. Weiyu Lin says:

    I’m glad that you find this post helpful! Thanks!

  11. Weiyu Lin says:

    Thank you for these euqstions! I actually never thought about that because I seldomly use my phone while it’s charging. I found some answers on Quora which seem reaonable. The answer may be: try not to use apps that heat up your phone while charging. The reason is that your phone gets hot when you charge it, and it’s very likely to be hotter if you play a game with it while charging. Using your phone in fact slows down charging rate, which is good for the battery, however, a higher temperature makes the battery feel sick. If you want to see the answers in detail, check this link:

  12. Liqun Yang says:

    A really good story to help me change the ‘charge habite’. I had a question about whether the phone has a similar function to laptop ‘switch between DC and AC’? When I charge the phone could I play as well? Will this habit also influence the phone battery?

  13. yufeizhang says:

    This is a really good blog post, because it contains useful advises for people to charge their smart phones. However, for me, I prefer to like charge my phone all night, because I think it is inconvenient to carry the charging cable and charger with me everywhere. One purpose of using smart phone is to make our life easier. But I can also get some good advises from you. For example, I will charge it before my smart phone’s electricity is running very low. Besides, I will charge it at a low temperature. Thank you very much!

  14. afujii says:

    This is very interesting topic and something I always wanted to know.

  15. Danni says:

    Awesome tips! This is something I’ve always wondered about but never bothered to look at scientifically. Great reminder that I can always do that with the little things in life! 🙂

    Though I am confused about the analogy between keeping an electron healthy and our body healthy. Or rather, I understand the parallel you are trying to draw, but I am not sure why electrons need to move around such that they will continue to do so. Don’t the negative charge of electron innately draws it to positive charges? Why does that need to be exercised?

  16. Lau Li Ken says:

    Ever since my previous phone started developing horrendous battery issues (you could call a friend only to find that the previously charged phone had started running on dregs) I’ve been increasingly worried about phone battery life. Paranoid, even!

    A great read to alleviate my worries about overcharging. I am well pleased to know it’s nothing to worry about. I also enjoyed the analogy at the end too.

    What a fickle bit of technology, can’t ever make them happy.

  17. elarsson says:

    Found this post really interesting and applicable to my everyday life! Thanks for sharing!

  18. Jemima James says:

    Thanks for the tips!

  19. loik says:

    That was a interesting and somewhat mindblowing read! Personally, I’m the type who tries to drain my phone down to when the “low battery” alert pops up before actually charging it, unless if I can’t help it. Same for my laptop.
    But for both, I still do leave it in to charge for longer periods than it takes to reach 100%.
    For my laptop, I’m rarely using it when I’m charging it (since I have my desktop computer anyway!) and there’s actually no light indicator for fully charged, only when low battery (some sort of Lenovo design flaw, perhaps?) unlike other laptops I’ve previously had.
    For my phone, it has some sort of battery care system which makes it stop charging at 100%, timed to when you wake up and become ‘active’ or according to your phone alarm clock? I used to not charge my very old phones overnight because of I didn’t want it to ‘overcharge’, but I do with this phone because of the promise of ‘battery care’. I wonder how this system works with programming the Li-ion battery to charge to full at that timing?
    Let me know if you happen to know the answer to that question!

  20. Yue Li says:

    Good to know how to charge my batteries right. It’s a little hard to understand why batteries go flat faster overtime, otherwise it’s a interesting read.

  21. Devanshi says:

    This is really interesting, thanks for sharing! I’ll definitely be trying some of these tips.

  22. tharding1 says:

    I’ve never seen any data on charging patterns, it’s interesting to know! I guess there is a lot of apocryphal ideas about some bits of technology like charging patterns. It will be interesting to see if there is a successor to Li batteries in the short or medium term future. Are you aware of any?