Why Two Power Banks With the Same Capacity Give Different Results

Everyone has had a similar experience, you buy a portable charger because it says 10,000mAh on the package. You've checked your phone's battery capacity and it has a 5,000mAh battery so it seems reasonably safe to say you'll get 2 full charges before running out of power.

Then when you begin using the charger, you charge your smartphone to '100%' and then realize there are already 1 or 2 lights blinking on the power bank before you charged your smartphone again. By the time you reach for your smartphone to charge it again it is at '60%' and by the time that you plug it in, the power bank has already exhausted its power supply and shut down.

What is happening? How can you purchase two various models of a power pack with the exact same amount of milliamps but get differing performance results? And why does one C-type charging bank seem to last forever and the other seems to go out of the way and be underwhelming?

In order to answer these questions we have to look beyond the marketing numbers that claim to represent the charge capacity of a product and instead look at what actually happens when power is transferred from a plastic case into your pocket.

The big "mAh" lie (well, it’s more of a misunderstanding)

When you see "10,000mAh" or "20,000mAh" on portable power banks, that number refers to the internal battery cells inside the device.

Here is the catch: those internal cells usually run at 3.7 Volts. However, to charge a phone through a USB port, that power has to be pushed out at 5 Volts (or even higher if you are using a fast charging power bank).

When a battery is "up-converted" from its nominal voltage, the voltage converted to a higher voltage will result in a "loss" of capacity. This loss of capacity occurs because of the difference in size and shape of the container to hold the same amount of water (a wide shallow bucket compared to a tall narrow bottle). Because of this difference between size and shape, there will be some spillage during the pouring process.

To put it simply, if you have a 10,000 mAh battery, this is not necessarily going to give you 10,000 mAh of "usable" power. In fact, usually you are only getting approximately 6,000-6,600 mAh of usable power from most batteries with this capacity. It’s usually referred to as "Rated Capacity" and is also one reason why one manufacturer may provide results inconsistent with the other. It could also indicate that one manufacturer uses better or less accurate methods to calculate conversion efficiency.

Efficiency: The silent energy thief

When we compare two different usb c pd power banks (both rated at 10,000mAh), one of them may last longer than the other after they both have been drained down by one full cycle of charging because of how efficiently they were charged.

Every time electricity moves, it creates heat. If your portable charger feels warm while it’s working, that heat is actually wasted energy. It’s electricity that should have gone into your phone but turned into heat instead.

Higher-quality power banks use better internal circuits that don't get as hot. A cheap, generic power bank might have an efficiency of 70%, while a reliable power bank Australia needs for those long outback drives or flights might hit 85% or 90%. In spite of not being a huge Percentage number; 15% can mean charging to 100% or stopping at 80% before the battery runs out of juice.

Fast charging: The speed vs. stamina trade-off

This paragraph is where the confusion starts. Everyone wants a portable charger that is capable of charging quickly, but no one wants to use a bulky wall socket-style charger for 3 hours.

Fast chargers are usually not as efficient at charging devices as a standard charger; this is because fast chargers provide an output of much higher than normal Voltage (typically 9V or 12V). Because of this, the Cell phone pulls more power much faster which creates additional heat and causes your batteries and chips to work harder.

The conclusion is that the faster you charge your device the more energy will be wasted in the charging process.

If you have two identical power banks:

1. One charges a phone at a standard, slow speed.
2. The other uses fast charging to finish the job in half the time.

The slow one will almost always get "more" total charge into the phone before it dies. If you’re on a long-haul flight and you just need the most juice possible, slow and steady actually wins. But for an everyday portable charger where you just need a quick boost between meetings, the speed is worth the energy trade-off.

Cable quality matters more than you think

Sometimes the power bank isn't the problem at all, it’s the "pipe" connecting it to your phone.

If you’re using a cheap, thin cable with a high-end usb c power bank, that cable creates resistance. If you thought that greater resistance equals greater heat, then you would be correct! By using a cheap or poorly made charging cable, your device could lose several watts of power to heat production before it even receives any actual charge.

So when choosing a power bank, you must ensure you purchase a very good quality USB-C cable. The best quality cables provide for the highest level of Power Delivery (PD) handshake between both devices so they can communicate and determine how to provide power with the highest efficiency possible.

Real-world scenarios: Why your results vary

Two of the most important considerations for using a power bank are power consumption and temperature. These factors are often overlooked when evaluating power banks.

The problem of using your phone while it is charging can be viewed through the lens of these two variables. By charging your mobile device, you're actually using the same power bank source; therefore when you charge your mobile device you use the same amount of energy consumed from the power bank.

As such, when your power bank is discharging to charge your mobile phone and at the same time you're using a GPS or playing a video game, you're consuming all of the power being supplied by your power bank to your mobile device. Consequently, although your mobile device is discharging from your power bank faster than normal, it may cause the overall performance of your mobile device to be somewhat unpredictable.

In addition to using the power bank, another factor to consider is temperature. Temperature changes how lithium batteries will respond to the energy they are receiving from a power bank, and the energy supply of the power bank will be affected if stored in either too cold or too hot an environment. When lithium batteries are stored in extreme environments (particularly hot areas such as on top of a car in Sydney) or very cold environments (like a freezer tent in Tasmania), the electrochemical reaction that occurs inside the battery will be impacted.

Just like other batteries, the lifespan of portable power banks is limited. The number of times you've charged your battery (300-500) will determine the maximum capacity the battery can hold (e.g., 10,000mAh). The number of cycles will also dictate how much energy that power bank can deliver to your device.

What should you look for?

When considering a purchase, you may want to look at both Speed and Size when reviewing the different options of power banks. However, before deciding on which Power Bank to buy, do not only take into account the highest number you see in each category, but think more closely about what you need from a Power Bank:

1. For Commuters: A slim portable power bank is great because it fits in a pocket. It might have less total capacity, but it’s easier to carry every day.
2. For Travellers: Look for an airline safe power bank. Most airlines limit you to 100Wh (roughly 27,000mAh). If you go over that, security might take it away. A power bank for travel needs to balance high capacity with these legal limits.
3. For Heavy Users: If you need a power bank for phone and tablet at the same time, look for multiple ports and high "Total Output."

The honest truth about "Capacity"

In simple words, don't expect 100% of what’s written on the box to end up in your phone.

When it comes to high-capacity power banks, one helpful rule of thumb is the "Two-Thirds Rule." This means that when you see a power bank claiming to have 10,000mAh capacity, you will realistically encounter around 6,500mAh of usable capacity and similarly; with a claim of having a 20,000mAh capacity, this would equal about 13,000mAh usable capacity in real-world scenarios.

If a manufacturer tells you that you will have "100% efficiency", they are lying and are not being truthful. Physics does not work that way and energy losses are a part of life.

Summary: How to get the most out of your portable charger

To maximize the efficiency and longevity of your Portable Power Bank, follow these simple rules;

• Keep It Moderate: Don't Store It In Very Cold Or Hot Temperatures.
• Don't Let It Charge To 0%: It Is More Efficient To Charge A Mobile Device From 20% To 80% Than To Charge It From 0% To 100%.
• In terms of charging ports: It Is Always Best To Use A Dedicated USB-C Port To Charge Your Portable Power Bank. This will provide greater efficiency for charging purposes.
• Turn off screens: If you are really trying to conserve battery life on your mobile device, you may choose to plug-in your mobile device and leave it unplugged for 30 minutes. This will put your device into a dormant state whilst providing the same amount of charge.

By understanding that capacity is not merely a number on a sticker, it will assist you in determining the proper tool to meet your power needs and expectations. Whether you are searching for a handy power bank that is suitable for camping trips in Australia or a small power bank that will fit into your handbag, knowing the reasoning behind the power behind your device provides a connection when it is most needed.