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HOW DOES THE POWER BANK WORK?

Power banks are devices that are used to charge mobile phones, tablets, laptops, mp3 players and mp4 players anytime and anywhere. With the use we subject are devices to, it is important to have a power bank to be able to keep these devices up and running all the time.

Power banks can give you uninterrupted access to play games on your laptops. Instant message on the internet, use social networking platforms and book airline, train and bus tickets at the drop of a hat.

There are certain specifications that you ought to keep in mind before laying your hands on the ideal power bank for your need.

Grab a power bank that is double in battery capacity to be able to charge your mobile phone, tablet, laptop, mp3 player and mp4 player at least once. Today I will introduce you How Does a Power bank Work? To understand things a bit better, let’s take a look at a block diagram of how these devices work, after that we will see some of the major and minor components of it.

Major components:

Moving on to the main question, How does a power bank work? To my knowledge all of these devices use Lithium Ion/Lithium Polymer battery as their power source, so in the inside they have these type of batteries. Remember this is the same type of battery that is inside of your phone, tablet, laptop or most of the portable devices that we use these days.

These cells are so popular and widespread due to their high weight to power ratio. Lithium batteries can provide about 300W per kg where the other ever popular lead acid can only do 180W per kg. So more power, less weight that’s what is needed on a portable device.

So we have got the battery for such devices, lithium ion or polymer. Now we need to make sure it can provide proper voltage and current to the device. Lithium cells has a nominal voltage of 3.7V and can go all the up to 4.2V while fully charged. But the USB ports that we use has 5V with strict regulation. So we need to change this cell voltage to 5V.

How can it be done?

Usually it is done by a boost converter that provides a steady 5V on its output regardless of the battery voltage being at 3.7V or 4.2V or anything in between them. If more than one cell is used. What I have seen is manufacturer uses them in parallel. So they can use the same circuit just have better service time. Although the one that I made, I used two 18650 cells in series and use a buck converter to lower the voltage to 5V. Either way output voltage is 5V, we got it on USB so we can charge any device. Another important thing about this boost converter is,

it usually limits the output current too, depending on the circuit it can provide different amount of current. In some cases, where it is suppose to charge a laptop however. The output voltage can be 12V or 19V depending on the model or depending on the device that it’s manufacturer is aiming at. So we have a power source inside and a circuit that can provide our desired voltage and current. Everything is fine so far but we need to charge this cell right?

So next part, charging the battery that is inside of them. Charging a lithium ion is a bit tricky. You have to make sure to put proper voltage and current in and change the charging profile. When necessary and you have to control the voltage otherwise it can blow up.

Lithium ion takes a steady/constant current up until they reach their 60-70% capacity then it charges at a constant voltage. Steadily declining the input current to them. So you need a charging circuit that have such ability. Also it is safe to use a charging current that is half of it’s amp-hour rating.

For smaller capacity power banks, usually an USB input is provided for charging it up. As smaller capacity devices have smaller cells it is easy to top them up with a smaller current from any USB port.

Larger capacity ones however include their own power brick or AC adapter with them to charge it from AC main line.

Now we have a working power bank that can take in power from USB or an AC adapter(similar one that is found with any phone, tablet or laptop, but might have a different output voltage). And charge a battery inside it and can power your device using that stored energy. Done? Not really, there are some more bits and pieces of stuffs in their. Let’s talk about them

Minor components

Usually these devices, or at-least the good ones have indicator that shows the battery percentage. So you can see how much power it has left or should you charge it or not. So we need a circuit that can sense the battery capacity . And show us by maybe a multi-color LED or maybe a bar graph or maybe with a LCD. Some of these devices have some built in meters for measuring voltage and current. Usually on the output section and they use LCD or LED display to show that. It without these circuits. The power bank will still work but they make stuffs a lot easier and more suitable for using.

There are some more circuit to ensure the safety of these devices, like temperature sensor or current sensor. What it does is while charging or supplying a load it keeps on checking. The battery or the circuit temperature to ensure that both of them are within their standard operating range. If something goes sideways it automatically turns itself off. They also measure output current too to see if the output current is within it’s limit, if not, it will automatically turn off.

Another protection circuit is there to protect the battery from going below a certain voltage level. Some battery has this protection built in but if it doesn’t have that circuit it might be added to the design to ensure good health of the battery.

This is pretty much how does a power bank work. But all the circuit blocks that I have mentioned here might not be available in many designs but reputed manufacturer will have them for sure.

There are huge amount of power banks available with many different capacities. And it is pretty overwhelming in most cases to select the perfect one. Yet simple advice go for the reputed manufacturer or the one with better warranty policy. Some power banks might come with torch light too, get them if you find it necessary.

Some power banks might have wireless or induction charging that uses different circuitry to make magnetic field to transfer power. This post is already kind of long so won’t get into details.

CAN I CHARGE MY POWER BANK USING THE MOBILE CHARGER?

It entirely depends on what your charger and powerbank are rated at, but: as a rule of thumb, if it uses USB, then the answer is very likely a yes.
Keep in mind that, depending on the powerbank’s capacity and the phone charger’s rated output. The powerbank may place a load on the charger which the latter will not be able to fully satisfy safely:

the powerbank may not charge fully,
the charger may become hot, or shut itself down due to overcurrent, and
the charging process may take a very long time to complete (assuming it ever does).
Cheap knock-off chargers that are known to catch fire may catch fire during this process. But the probability is generally low. 😉
Additional note: be aware that some very old chargers designed to work with Nokia feature-phones (the ones with physical keyboards) may use a micro-USB port. But actually deliver ~3.8V (which is not only incredibly insufficient, but also wildly outside of USB specification). This is due to the fact that Nokia has historically been caught using the micro-USB port as a feature port combo (back in the days when they still used 3.8V to charge their batteries). Notably, all of such chargers I’ve seen have the cable moulded into the charger.

POWER BANK RENTAL STATION, WHAT ABOUT THEM?

Power bank rental companies began to appear three years ago amid ridicule by Chinese netizens. Then in a span of four days in 2017, the industry raised USD 111 million. More charging stations popped up in train stations, hospitals, malls, restaurants and other public spaces. You pay, charge your phone and leave. But mind you, the skeptics are still lurking. As Chinese startups brace up for a “capital winter”, the lens is back on the market for power bank sharing.

The development of the sharing economy

Shared portable phone chargers are no longer the hot topic among venture capitalists. Many companies have given up. LeDian (乐电), for instance, was founded in March 2017 and closed in October the same year. According to business portal ICEO.com.cn, which has published a report on the industry’s situation, the players Laidian (来电), Jiedian (街电 ), Xiaodian (小电) and Guaishou (怪兽) are likely to survive.
On May 5, 2017, when news of Jumei International investing CNY 300 million in Jiedian was out. The son of Wang Jianlin, one of China’s richest tycoons, posted on WeChat: “If shared portable phone chargers can succeed, I will eat my own arm”. The comment was viral.
Three hours later, Jumei’s CEO Chen Ou posted on microblogging site Weibo: “Wang Sicong, thank you for your attention. Entrepreneurship is about taking risks, we know the chances for a startup to succeed are slim.”

After the shared bicycles boom. There was an explosion of startups that focused on the “sharing economy”: shared umbrellas, shared concrete mixers and even shared basketballs. Investors who were late to the shared bikes craze were desperately looking for the next unicorn.

Co-founder of a mobile phone power bank startup based in Shanghai, who prefers to use the alias Hu Tian, said no investor showed interest in his idea in 2015. He had failed to find funds for his startup. However, just a year later, the tide had changed. Investors contacted him so often that it was he who had to turn them down. Hu says the threshold in the industry was low, and most startups only had to show some numbers to get enough financing.

During interviews, CMO of Laidian, Ren Mu, likes to stress that they were the first to come up with the idea back in 2014, before shared bikes were in vogue. In the first half of 2016. The company’s finances were tight, after almost spending the CNY 10 million they had painstakingly raised from the company’s founding team. Facing indifference from investors, the company’s entrepreneurs invested their own money again, CNY 7 million in total. They tried out several locations for renting stations. Eventually, they could lease each power bank 7 or 8 times a day in the best performing locations.

In the second half of 2016, following the success of shared bikes, investment institutions started to pay attention to shared power banks. In April 2017, Laidian received investment from SIG and Redpoint China Ventures.

As opposed to Laidian, which endured many hardships before things started to work, Jiedian had it easy. From its inception, Laidian used smaller stations that could fit on a restaurant table. Users could take the charger with them and leave them in a different station whenever they want. Jiedian, on the other hand, was using a big station in each location, which was not as convenient as the smaller ones. If customers take chargers with them and forget to return, the deposit paid upon registration compensates the companies.

Some companies install big charging stations at malls. Others set up ones that fit on a restaurant table.
Tang Yongpo is the founder of Xiaodian, another player the market is hopeful about. Thanks to his expertise in understanding the shared portable chargers’ industry. He was able to secure a financing of hundreds of millions of yuan from players like Tencent, Sequoia, Gaorong VC and CDH in March 2018. Xiaodian offers charging stations on restaurants’ tables and other venues, but they are not portable. According to Tang, “this model is more convenient than the portable power bank”.

Among investors of Guaishou are big firms such as Gaorong VC, Shunwei and Xiaomi. Thanks to its partnership with Xiaomi, Guaishou has the advantage of supply of reliable and good quality devices.

With such fierce competition, how big can a company grow?

Henry he says when the industry was booming, restaurants, malls and other locations started to charge much higher fees to let companies offer their portable chargers. The most popular spots were charging thousands or even tens of thousands of yuan to allow the presence of a company. The fierce competition led these firms to sometimes offer twice as much as their competitor to set up on a particular spot.

WILL CHARGING WITH A PORTABLE POWER BANK DAMAGE CELLPHONE’S BATTERY LIFE?

The actual phone charger is in your phone. It doesn’t matter where the power comes from, charging is always the same.

Modern Lithium Ion and Lithium Poly cells do benefit from being “topped off”. There is no lifetime penalty for charging before they’re depleted. In fact, letting a battery get too low will reduce its lifetime. You count on the phone’s software to prevent the most extreme form of this, but it’s far better to charge before the battery dies.

A typical Lithium battery will have between 300 and 500 full charge cycles. So if you let your phone die every day, you could need a new battery in less than a year. Most people don’t do that, and so it’s more common to get two or so years out of that cell.

Hybrid ccars don’t have dramatically different batteries, but they only run through a fraction if the battery’s capacity. If you had a charger that would only charge to about 80% of the battery’s capacity, and the phone cut off at 20% or so, the battery might last a decade (assuming that power cycling is the only aging mechanism… sone Lithium chemistries don’t last more than 3-5 years even without any use). Of course, you’d hate the battery life, and the phone makers would eliminate one reason people upgrade to new phones, so this is unlikely to happen.