Taking care of one’s batteries has become increasingly important now that consumer electronics come with sealed batteries that aren’t user replaceable. Proper battery utilization can prolong long-term battery life and prevent unwanted trips to the service center for battery replacements. What follows is a run-through of the battery technology used in personal electronics and how one should use and charge their devices to maximize battery longevity.
This article uses information from in-depth write-ups on lithium-ion batteries published at Battery University; additional articles from Apple, Lifehacker, and Ars Technica were also referenced. Links to the articles are listed below.
- Ask Ars: What is the best way to use a Li-ion battery?
- Ask Ars: The best way to use a lithium-ion battery, redux
- How to Prolong Lithium-based Batteries
- Charging Lithium-ion
- How to Charge and When to Charge?
- Basics About Discharging
- Summary of Do’s and Don’ts
- Battery Pack Overview White Paper
- New Developments in Battery Chargers
- Will Lithium-Ion Batteries Power the New Millennium?
- Dell, R., & Rand, D. A. (2001). Understanding batteries. Cambridge: Royal Society of Chemistry.
Lithium Ion Battery Technology
The major points of confusion with battery usage are related to the battery technology implemented in the gadgets. Today’s laptops, smartphones, and tablets all use rechargeable lithium-ion batteries. All references to “battery” or “rechargeable battery” in this piece of writing will refer to lithium-ion batteries unless otherwise specified. Lithium-ion batteries have the following properties:
Lithium Ion Battery Charging
- Lithium-ion batteries are not susceptible to “battery confusion” as they do not have “battery memory” – irregular charging of rechargeable batteries will not prevent the batteries from charging to full when given enough charging time. Hence, they do not need to be fully discharged before they are charged or fully charged before they are unplugged.
- The battery-reading circuits in smartphones, laptops, and tablets can get confused by erratic charging cycles. Said devices need to be calibrated on occasion so that battery capacity is properly measured.
- The chemicals inside the batteries are stressed when maintained at high internal voltage. Battery capacity is directly related to battery internal voltage, so leaving rechargeable batteries at full or near-full capacity for long periods of time will cause the battery to deteriorate.
- Lithium-ion batteries should not be kept at 0% charge. The charging circuit used for rechargeable batteries requires voltage from the battery to operate, and leaving battery charge at zero increases the chances that the charging circuit fails to charge the battery.
- Lithium-ion batteries have a maximum safe value of voltage. If rechargeable batteries are charged to above the safe voltage of 4.2 V, they begin to deteriorate and become a safety hazard.
- For long-term storage, lithium-ion batteries should be left at 40 – 50% to allow for idle discharge in the battery without placing unneeded stress on its internal chemistry.
Lithium Ion Battery Discharging
- Lithium-ion batteries naturally lose capacity over multiple discharge cycles 1.
- The long-term degradation of lithium-ion batteries is dependent on the depth of discharge 2 even when consuming the same total amount of energy. A full discharge cycle (using a battery from 100% to 0% without charging) will wear out a battery more than 4 separate discharges of 100% to 75%.
- Current draw also affects long-term battery life. A higher current/power draw is more stressful to a battery than idle-state, low-current operation even if the total energy used is equal.
- Elevated temperatures accelerate the deterioration of battery capacity.
- Using the battery at low voltage/capacity is not ideal for the long-term life of the chemicals inside a rechargeable battery. Delivering power at low remaining voltage places additional strain on the battery and affects its long-term endurance.
How to Use Maximize Your Battery’s Effective Life and Capacity
With the principles of lithium-ion batteries listed above, best-case scenarios for battery usage can now be discussed. I’ll be doing this in question-and-answer form while citing the above principles plus some additional references:
I’ve just received a [insert gadget with rechargeable batteries here], should I drain it to 0% or charge it to full before using it?
The gadgets I’ve bought have had batteries with roughly 40 – 50% charge out of the box, which matches the standard storage procedure for batteries. Apple and Battery University both instruct users to fully charge their new gadgets upon opening. This helps the internal battery determine its full capacity after a long period of idle time.
Should I wait for my battery to reach 0% before charging it?
Draining the battery to 0% before charging provides no benefit to long-term battery life. Rather, draining the battery to critical levels before charging will be more taxing to the battery and reduce its longevity. It is ideal to charge gadgets before they reach their low-charge state.
Can I use my phone/laptop/tablet while it is charging?
It is ideal for batteries to charge when turned off, but using your device while it is charging will not damage the battery. Battery University states that using the device while charging may cause some small errors in device calibration, but the practice will not damage the battery.
Should I always charge my gadgets to 100%? If I can’t charge it fully to 100%, will I damage the battery?
Lithium-ion batteries can be charged at any time and can accept partial charges. Charging a device from 80% to 100% will not damage battery capacity, nor will charging it from 40% – 80%. Hence, people who intermittently charge their devices during the day will not damage their device’s long-term battery life. Regular charges during the day should actually be better for the battery; keeping the battery at a moderate charge level prevents the aforementioned low-charge state that hurts battery longevity.
Can charge my gadget overnight without damaging it?
You’re contradicting yourself, you said that lithium-ion batteries can’t take too high a voltage without breaking. Won’t leaving it overnight cause it to overcharge and fail?
Not to fake people out, but most modern gadgets with lithium-ion batteries also integrate protection circuits in their internal charging systems that prevent the battery voltage and temperature from going too high or too low. These circuits cut off charging supply at 100%, let the battery drain normally, and supply an intermittent topping charge current as needed to maintain battery charge at close to 100% without exceeding safe voltages. Technical details of protection circuitry can be read in miscellaneous references I’ve listed above.
Not every rechargeable electronic device has the appropriate safety measures I’ve described. I’ve personally had a generic portable speaker blow out after leaving it plugged into my computer for too long. Said speaker produced grotesque sound in its death throes, too. Smartphones, tablets, and computers from branded manufacturers can be charged overnight just fine, however. Phone, tablet, and laptop manufacturers mostly source their motherboards and systems-on-a-chip 3 from suppliers like Intel, Qualcomm, or Mediatek, which all provide the needed protection circuity in their designs to prevent overcharging.
It is still ideal for the device and battery to be disconnected from power upon reaching acceptable battery capacity. As mentioned, batteries suffer from strain when held at high voltage, so unplugging the charger upon reaching full capacity can help extend battery longevity.
Does using power banks help extend the long-term working life of my battery?
Phones and tablets don’t accept power directly from the power bank/charger. Even while connected to by power banks or other power inputs, phones and tablets will draw power from its internal battery while the battery is being charged by the connected power supply. Hence, using power banks or keeping a phone or tablet charged all the time won’t result in “free usage” in terms of battery health.
That being said, keeping battery voltage/charge at healthy voltages is better than letting it drain to critical levels. Power banks help extend battery lifetimes by preventing the low-battery-level operation that compounds battery deterioration.
Laptops, on the other hand, can accept AC power directly. Unless you’re expecting a brownout/blackout, keeping a laptop plugged into AC power with the battery physically disconnected will obviously extend battery lifetime. Laptops with integrated batteries don’t enjoy this advantage though.
How should I use my gadgets to prolong my battery’s lifetime?
At this point in the write-up, it is clear that battery deterioration originates from different factors. Batteries are strained by being held at high voltage, by operating at low voltage, by supplying large amounts of current or power at a given time, and by running at elevated temperatures. Battery lifespan can hence be maximized by avoiding these points of battery abuse.
Batteries retain their lifespan better under usage conditions with shorter and low-power loads at lower temperatures. This means that draining 90% of your battery’s capacity when leaving it in a drawer will reduce battery lifespan less than if you drained 90% of your battery playing games. This doesn’t mean that you shouldn’t play games, but keep in mind that regular strenuous usage will shorten battery lifespan.
Batteries also have ideal operating voltages. Battery University clearly presents that keeping batteries at a voltage lower than their maximum 4.2V will prolong their long term health. At the same time, actually using the battery at low voltage will strain the battery more. This means that battery capacity and battery lifespan have to be balanced based on user need.
Ars Technica summarizes frugal battery usage by emphasizing regular and frequent charging, shallow discharges of the battery, and low-current-low-temperature usage of the battery when possible. Going from ~ 90% to 60% regularly with intermittent charges will be better for battery longevity than always draining the battery from full to empty before charging. Gizmodo, Yahoo, Lifehacker,and Battery University all present similar strategies to preserve battery lifespan. Maintaining the battery at an intermediate voltage between 90 and 60 percent reduces the time the battery spends idling at high voltage or draining at low voltage. Additionally, users are encouraged to avoid the high-load and high-temperature condition that significantly affects battery lifespan. This prescribed usage method hence correlates properly with the battery principles that have been discussed.
Let’s repeat the consensus on ideal battery usage: maintain battery charge somewhere between 40% to 80%, go no lower than 20% charge in the worst case, charge frequently, and avoid high-temperature, high-power-draw usage scenarios.
My phone is draining its charge unnaturally. It started at 100% charge in the morning and reached critical charge by noon! Is there something wrong with my battery?
Following the regular charging methods prescribed can lead to the battery reading circuits in gadgets not reading charge properly. A device may read that the battery has been fully drained and shut off even when the battery has charge remaining. It is recommended that you calibrate your battery every 2 months or so by performing a full discharge from 100% to 0% and then charging the device back to full while it is turned off.
A more likely reason for abnormal battery discharge is that Facebook draining your battery in the background. Read this article on how Facebook gobbles up battery even while not active and how you can fix it on iOS. Here’s another article on how Facebook hammers your battery. Android users should install Greenify to force Facebook to go to idle/sleep state or install an alternative Facebook app altogether.
Summary and Quick Points
Modern computing devices have veered away from user-replaceable batteries, which adds importance to properly managing battery usage. The principles behind rechargeable battery operation and the best practices for maintaining its longevity have both been discussed in this write-up. Users are advised to maintain battery voltage between 40% to 80% while going no lower than 20%, to charge their devices frequently, and to avoid high-temperature, high-power-draw usage scenarios when possible. Commonly asked questions regarding battery charging and usage have also been answered. People interested in learning more about lithium-ion battery technology should refer to the links listed above, especially the articles on Battery University.
I’ll finish with some quick points that I didn’t squeeze into the write-up previously:
- Battery University posts a handy table that summarizes lithium-ion battery usage and charging on this page. If you wanted a tl;dr summary, that table is it.
- Wireless chargers sound great for keeping gadgets charged all the time, but wireless chargers are actually pretty inefficient and convert a lot of the supplied power into heat. Heat is bad for batteries. I personally recommend buying more USB charger cables and leaving them at the places where you spend your time most.
- Irresponsibly coded apps will wreak havoc on battery life by keeping gadgets in a power-on state. Modern gadgets get their longevity from rushing their tasks to completion and switching to an low-power idle state. The mentioned app behavior and the ideal OS operation are obviously antithetical. On Android forums, the action of an app to keep a device in its active state instead of switching to idle is called a wake-lock. Greenify on Android helps force apps to sleep and mostly prevents wake-locks from occurring, hence encouraging the low-power idle state desired for extended battery life. On iOS, general procedure is to monitor which apps are accessing data in the background and turn off background data for apps you don’t prioritize. Common culprits on both platforms are Facebook, social networks, social games, and chat apps.
- It’s nice of Samsung to provide replaceable batteries on the Galaxy S5, but it’s not like anyone actually buys a second battery until they want to replace their old one for good.
- A discharge cycle is a unit of measurement for battery utilization. Standard usage of the term “one discharge cycle” refers to one cycle of consumption of a battery’s full capacity. ↩
- The depth of discharge is conventionally defined as the fraction of a battery’s full capacity delivered during one usage cycle without charging. Depth of discharge is the difference the battery’s full capacity and the remaining capacity at the end of the usage cycle before charging, e.g. using a battery from 100% to 73% is measured as 27% depth of discharge. ↩
- A system on a chip, with the acronym SOC, is a single electronics block that includes the processor, sound chip, wifi, telephony/3G chip, and the interfacing technology a phone or tablet needs to function. Its equivalent in desktops and laptops is the motherboard. An easy-to-understand overview for SOCs can be read at Ars Technica. ↩