Picture this: You're in the middle of a long-awaited hiking adventure in a remote mountain range. The stunning views are breathtaking, and you've been eagerly capturing every moment with your phone. But as day wears on, your phone is starting to blink that dreaded low-battery warning.
Thankfully, you remembered to bring your power bank, your trusted travel companion. Before setting off on this journey, you charged it to its full capacity, relying on the label that boasted it could recharge your phone multiple times.
But as you plug your phone into the power bank, your hopes start to fade. After just one charge, the power bank's indicator lights are already dwindling, and your phone is still far from being fully charged. What went wrong?
This isn't a one-off experience. Countless power bank users around the world have faced this exact same disappointment. There's a persistent and often frustrating gap between the rated battery capacity printed on the power bank's packaging and the actual amount of charge that makes it to your device. Is your power bank lying to you?
The rated capacity is like a promise on paper. It tells you how much power the internal batteries of the power bank are supposed to hold under specific conditions set by the manufacturer, such as temperature, discharge rate, and voltage. However, the real-world capacity, the amount of charge that actually reaches your device in the hustle and bustle of daily life, can be a different story.
It might seem confusing at first glance. But fear not! This article is here to be your guide. We'll break down the difference between these two capabilities, explain why this gap exists, and provide you with practical tips you need to make the best-informed decisions when choosing a power bank. So, let's dive in and uncover the truth about power bank capacities!
Actual Capacity VS. Rated Capacity: What's the Difference
When you first set your eyes on a power bank, the rated capacity is the number that immediately catches your attention. It's prominently displayed on the packaging, often a large, bold printed figure like 10,000 mAh or 20,000 mAh. This rated capacity is essentially the theoretical maximum amount of electrical charge that the power bank's internal battery can hold when it's fully charged. It's like a stated potential, a sort of promise from the manufacturer about what the power bank could potentially offer in ideal conditions.
The actual capacity of the power bank, on the other hand, is the amount of charge that your device will actually receive during the charging process. This is the real-world, practical amount of power you can rely on to juice up your device.
As we've seen, the difference between the two can be quite substantial. The rated capacity is based on laboratory-scenario testing. It assumes that everything from the battery's performance to the charging process is without any hitches. However, in real-life situations, there're numerous factors that come into play. In the following section, we'll delve deeper into these elements, unearthing the hidden truths that make the stated capacity just a fraction of the full story.
Conversion Efficiency: Why it Matters
One of the main reasons for this is the conversion efficiency. Power banks don't transfer energy from their internal batteries to your device with 100% efficiency. There are losses during the conversion process, mainly due to heat generation and the inefficiencies of the circuitry. For example, if a power bank has a rated capacity of 10,000 mAh, and an energy conversion efficiency rate of around 80%, the actual amount of charge that can reach your device would be around 8000 mAh.
Understanding Actual Capacity
Usually, the power banks are made with 3.7V lithium-ion battery cells. And the printed capacity is based on 3.7V as well. But when it comes to charging a smartphone, which usually requires 5V, the power bank has to boost the voltage. This voltage increase is essential for the charging process to take place.
However, this voltage-boosting process isn't without consequences. It leads to a decrease in the total amount of electricity that the power bank can output. Then the actual capacity of the power bank needs to be calculated as below:
Actual Capacity = (3.7V * Rated Capacity) / 5V
Think calculating a power bank's capacity is a piece of cake? Hold on, it's way more complex!
Power Loss: The Hidden Factor You Can't Overlook
Power loss is a crucial factor that gets overlooked in basic calculations. This loss occurs predominantly during the voltage conversion from the power bank's 3.7V internal voltage to the 5V needed for charging devices, often manifesting as heat.
The amount of power loss is determined by the following factors:
• Battery Quality: High-quality batteries are power-efficient and degrade slowly. Low-quality ones, on the contrary, start losing power rapidly after just a few charge-discharge cycles.
• Circuit Quality: Poor-quality internal circuits waste a significant amount of power as heat during voltage conversion. In contrast, well-designed circuits can minimize this loss. So, the next time you're choosing a power bank, think about what's inside!
• Battery Age: As you use a power bank more and more, its battery weakens. Batteries that have endured numerous charging cycles lose far more power compared to new ones.
• Storage Conditions: Temperature significantly affects battery life and performance of lithium-ion batteries. To maintain power banks' optimal performance, it is recommended to store and use them in cool environments.
How Do You Calculate Actual Capacity
With a deeper understanding of power bank functionality, we can calculate a power bank's actual capacity more accurately for real-world scenarios using the formula:
Actual Capacity = 3.7V * Rated Capacity * Efficiency Rate / 5V
Formula explanation:
- Rated Capacity is the rated capacity indicated on the power bank (e.g. 10000mAh).
3.7V is the nominal voltage of the lithium battery. - Efficiency Rate is the efficiency of the power bank, usually due to losses in power conversion (typical range is 85%-95%, depending on the specific product).
- 5V is the voltage output by the USB, and the output voltage of the power bank is usually 5V.
Substitute into the calculation example:
Assuming the power bank is 90% efficient:
calculate:
Therefore, a 10000mAh power bank actually has a capacity of about 6660mAh, which is the capacity that can be used to charge other devices.
Table example:
| Rated Capacity (mAh) | Actual Capacity (85% Efficiency, mAh) | Actual Capacity (90% Efficiency, mAh) | Actual Capacity (95% Efficiency, mAh) |
|---|---|---|---|
| 10000 | 6290.0 | 6660.0 | 7030.0 |
| 15000 | 9435.0 | 9990.0 | 10545.0 |
| 20000 | 12580.0 | 13320.0 | 14060.0 |
Conclusion: Practical Advice for Making the Right Power Bank Selection
As we've discovered, the relationship between a power bank's rated and actual capacity is intricate. Factors such as voltage conversion and power loss can create a significant gap, making it seem as if our power banks aren't as powerful as they claim. So, when hunting for the perfect power bank, it's crucial to look beyond the rated capacity.
Instead, prioritize power banks with clear and precise markings. These details are a tell-tale sign of a trustworthy manufacturer. Quality should be at the top of your list too. Seek out power banks crafted from top-notch batteries and electronic components. This ensures better performance and a longer lifespan.
Moreover, how you use and maintain your power bank matters. Keep it in a cool, dry spot and refrain from over-charging or over-discharging it. This simple care routine can extend its usability and keep it operating at its best.
Pisen is renowned for its high-quality power banks that feature clear capacity markings, reliable voltage conversion, and durable build quality. Meticulously designed to fuel your daily adventures, Pisen power banks add not only a touch of convenience, but also make the most out of every charge. Whether you're commuting, traveling, or simply going about your day, Pisen power banks are a reliable companion that won't let you down.
Related reading:
Power Bank Capacity: What You Need to Know Before You Buy
Portability vs Capacity: The Best Power Bank for Your Devices
Leave a comment
This site is protected by hCaptcha and the hCaptcha Privacy Policy and Terms of Service apply.