Although lithium batteries have a wide range of applications, including in cars, electric vehicles, mobile phones, tablets, laptops, and many other devices, and perhaps even more devices will use them in the near future, for now, mobile phones and tablets are still the most commonly used lithium battery-powered devices. Therefore, it is necessary to provide special usage instructions for mobile phone lithium batteries.
1. Charging
It's important to note that lithium batteries enter a dormant state after being stored for a period of time, at which point their capacity is lower than normal, and their usage time is shortened. However, lithium batteries are easily activated; just 3-5 normal charge-discharge cycles are sufficient to activate them and restore their normal capacity. Due to the inherent characteristics of lithium batteries, they have virtually no memory effect. Therefore, new lithium batteries in a user's mobile phone do not require special methods or equipment for activation. This is not only theoretically true, but in my own experience, using the standard charging method from the beginning—a "natural activation" method—is the best approach. Regarding the "activation" of lithium batteries, many claim that charging time must exceed 12 hours, repeated three times, to activate the battery. This claim of "charging for more than 12 hours for the first three times" is clearly a continuation of the misconception from nickel batteries (such as nickel-cadmium and nickel-metal hydride). Therefore, this claim is fundamentally flawed. The charge-discharge characteristics of lithium batteries and nickel batteries are very different, and I can clearly state that all the serious, official technical documents I have consulted emphasize that overcharging and over-discharging can cause significant damage to lithium batteries, especially liquid lithium-ion batteries. Therefore, it's best to charge your phone according to the standard time and method, and especially avoid charging for more than 12 hours. Generally, the charging method described in the phone's instruction manual is the standard charging method suitable for that phone.
Furthermore, lithium-ion battery phones or chargers automatically stop charging once the battery is fully charged, unlike nickel-cadmium battery chargers which offer the supposed "trickle" charging for over 10 hours. In other words, leaving a fully charged lithium-ion battery on the charger is pointless. Since no one can guarantee the battery's charge/discharge protection circuit will remain unchanged or flawlessly reliable, your battery will be constantly teetering on the edge of danger. This is another reason we oppose prolonged charging. Additionally, on some phones, if the charger isn't removed after a certain charging time, the system not only doesn't stop charging but also begins a discharge-charge cycle. While manufacturers may have their reasons for this, it's clearly detrimental to the battery and the phone/charger's lifespan. Also, prolonged charging often requires overnight charging, which is problematic given my country's power grid, where voltage is often higher and fluctuates significantly at night. As mentioned earlier, lithium-ion batteries are delicate and far less tolerant of voltage fluctuations during charging and discharging than nickel-cadmium batteries, adding further risks. Finally, it's crucial to understand that lithium-ion batteries are also unsuitable for over-discharge, as this is equally detrimental. This leads to the following question.
2. When should charging begin during normal use?
On forums, you often see the claim that because the number of charge-discharge cycles is limited, you should completely drain your phone's battery before recharging. However, I found an experimental table about lithium-ion battery charge-discharge cycles, and the data on cycle life is listed below:
Cycle life (10% DOD): >1000 cycles
Cycle life (100% DOD): >200 cycles
DOD stands for Depth of Discharge. As the table shows, the number of rechargeable cycles is related to the depth of discharge; the cycle life at 10% DOD is much longer than at 100% DOD. However, when considering the relative total capacity of actual charging: 10% * 1000 = 100, 100% * 200 = 200, the latter's complete charge-discharge is still better. Under normal circumstances, you should recharge according to the principle of using up the remaining battery power before recharging. However, if the battery is not expected to last the entire day the next day, you should start charging promptly. Of course, if you're willing to carry a charger to the office, that's another matter. When you need to charge for an upcoming important event that will cause heavy communication, even if the battery still has a lot of power, you can charge it in advance, because you haven't actually lost "1" charge cycle life, only "0.x" cycles, and often this x will be very small. The principle of using up the remaining battery power before recharging doesn't mean you should go to extremes. A widely circulated saying, similar to long charging times, is "try to use up the phone battery power completely, ideally until it automatically shuts down." This practice, originally used in nickel-cadmium batteries to avoid the memory effect, has unfortunately also been adopted in lithium-ion batteries. There have been instances where people continued using their phones after receiving low battery warnings, continuing until the phones automatically shut down. In one such case, the phone became unresponsive to charging and powering on, requiring repair. This was because the battery had been over-discharged, resulting in excessively low voltage, rendering it incapable of charging and powering on.
3. Important tips for the correct use of lithium battery mobile phones
In summary, my most important advice regarding charging and discharging lithium battery mobile phones is:
1. Charge according to the standard time and procedure, even for the first three times;
2. When your phone displays a low battery warning, you should start charging it as soon as possible;
3. Lithium batteries do not require special activation methods; they will activate naturally during normal phone use. Insisting on using the widely circulated method of "activating with three 12-hour long charges" will not be effective. Therefore, all practices that pursue 12-hour ultra-long charging or using lithium battery phones until they automatically shut down are incorrect. If you have been following these incorrect methods, please correct them as soon as possible; it may not be too late. Of course, if the phone and charger's own protection and control circuits are of good quality, the protection of the lithium battery is fairly guaranteed. Therefore, understanding the charging rules is key, and in some cases, compromises can be made. For example, if you find that your phone must be charged before you go to sleep at night, you can start charging it before going to bed. The crucial point is to know the correct method and not deliberately follow incorrect methods.
II. Battery Maintenance
In reality, there aren't many usage precautions to take with batteries; in other words, even if you were, they wouldn't be very helpful. The number of times a battery can be used depends more on individual differences in the battery's manufacturing process than on how it's used. Aside from the battery's inherent quality, its lifespan is limited. Once a battery leaves the production line, its lifespan begins to decline. Regardless of whether you use it or not, the lifespan of a lithium battery is only two to three years. One of the major reasons for battery capacity decline is the increased internal resistance caused by oxidation. Eventually, the electrolytic cell resistance reaches a point where, even if the battery is fully charged, it cannot release the stored charge. Many people believe that lithium batteries should be charged for more than 16 hours for the first time to fully activate them. This is unfounded; it's a charging method used for older nickel-metal hydride or nickel-cadmium batteries and doesn't apply to lithium-ion batteries. These lithium polymer batteries theoretically have no memory effect, or if they do, it's negligible. Therefore, charging for about 3 hours is sufficient. If the charging indicator shows it's complete and you don't need external power for the time being, you can unplug the power cord without waiting that long.
Myth 1: A PSP needs to be charged and discharged three times to activate the battery. Unless the PSP you bought is a product that has been in stock for more than a year, you don't need to do this. Modern battery cells are already activated at the factory, and they undergo another activation-like test when packaged into a PSP battery. Therefore, the battery you receive is already activated; performing three charge-discharge cycles only unnecessarily increases battery wear.
Myth 2: The first charge must be 12 hours. This might have worked for early NiMH battery devices without battery control circuitry, but it's a joke for today's PSPs with their intelligent charge/discharge control modules. Once the PSP battery is fully charged, the charging current is automatically cut off, and the system displays it as "external power." Even if you continue charging for 120 hours, the status won't change. Generally, it's fully charged in 3 hours; the remaining "charging" is just a waste of time. Instead, you should completely discharge the battery before recharging a new device.
Myth 3: Batteries need to be fully charged and discharged once a month. For nickel-metal hydride batteries with a strong memory effect, this is necessary. However, for lithium-ion batteries, this cycle is too frequent. Lithium-ion batteries theoretically eliminate the memory effect, or if it exists, it is greatly reduced to a negligible level. If you use the battery frequently, you should discharge it to a relatively low level (about 10-15%) before recharging. However, discharging it to the point where the device cannot even turn on (0-1%) is considered a deep discharge, which can cause significant damage to the lithium-ion battery. Generally, doing this every two months is sufficient. If you rarely use the battery, then doing this every three months is enough.
Myth 4: Using the device while charging, or continuing to use external power after charging, will damage the device and battery. This is the most ridiculous argument. How much of the theoretical explanations regarding hole electrons, secondary charging, and other mechanisms actually apply in practice? The battery industry and academic circles are not unified on this point. If there are disagreements on the theory, how can it guide actual consumer use? Battery wear is divided into normal wear and damage. The wear caused by using external power and using the device while charging is well within the normal wear range. In other words, no matter how systematic the theoretical maintenance measures are, the battery will age. This is like how even the most miraculous cosmetics and skincare cannot prevent a beautiful woman from becoming an old woman; at most, they can only delay it. But how much real effect does superficial embellishment have? This is something that cannot be explained by theory—respecting actual usage experience is the correct and scientific approach. Some might say that the only way to avoid battery aging is not to use the device (which is why many people choose to remove the battery), but this defeats the purpose of the PSP's portability, and even when stored in a sealed state, the battery will naturally age over time. Batteries are actually a semi-consumable item. As long as batteries bring you enough convenience and joy, I think their sacrifice is worthwhile.
