Yes, you can charge a power bank with another power bank, a process often called “daisy-chaining” or “pass-through charging.” This essential tech hack can be a lifesaver when you’re low on outlets but have multiple power banks. We’ll explore the nuances, safety, and best practices to ensure you’re never left powerless.
Ever found yourself in a situation where your phone is at 5% battery, your laptop is about to die, and your only hope – your trusty power bank – is also depleted? It’s a modern-day crisis! You might then wonder, “Can I charge a power bank with a power bank?” The answer is a resounding yes, but it’s not always as straightforward as plugging two devices together. This guide will demystify the process, cover the safety considerations, and reveal how this simple technique can be a true genius move for staying powered up on the go. We’ll break down exactly how to do it, what to watch out for, and when it makes the most sense to employ this handy trick.
The Ultimate Power Bank Pairing: Can I Charge a Power Bank With a Power Bank?
Charging a power bank using another power bank is a common and often necessary practice. This technique, sometimes referred to as “daisy-chaining,” allows you to replenish one portable charger from another, ensuring you have more power available when you need it most.
This is the core question many users have when faced with a power shortage and multiple portable chargers. The good news is that, in most cases, the answer is yes. It’s a technique that’s becoming increasingly relevant as we rely more on portable devices for our daily lives. Understanding how it works, its limitations, and potential risks is key to mastering this power-saving strategy.
Understanding the Basics: How Power Banks Work
Power banks are essentially rechargeable batteries designed to store electrical energy. They contain a battery cell (or multiple cells), a charging circuit to manage input and output power, and ports (usually USB) for connecting devices. When you charge a power bank, you’re feeding electricity into its battery. When you use it to charge another device, you’re drawing that stored energy out.
This fundamental understanding is crucial because it explains why charging one power bank from another is possible. You’re simply using one power bank’s output to act as the input for the other.
The “Daisy-Chaining” Technique Explained
“Daisy-chaining” power banks refers to the act of connecting one power bank to another, and then connecting your device to the second power bank. More simply, it’s charging a power bank using another power bank. This is typically done using standard USB cables.
You’ll connect a USB cable from the output port (usually USB-A) of the first power bank to the input port (usually Micro-USB or USB-C) of the second power bank. The second power bank then acts like any other device you’d charge, receiving power.
Is It Safe to Charge a Power Bank With a Power Bank?
Generally, it is safe to charge a power bank with another power bank, provided you use compatible cables and ports. However, it’s crucial to be aware of potential inefficiencies and to avoid overloading or damaging your devices.
Safety is paramount when dealing with electronics and batteries. While the act itself is usually safe, there are specific precautions to take. Using the wrong cable or pushing the devices too hard can lead to issues.
Cable Quality: Always use reputable, high-quality USB cables. Cheap or damaged cables can overheat or fail, posing a risk.
Port Compatibility: Ensure the ports you’re using are designed for charging and data transfer (though data transfer isn’t needed here). Standard USB-A to USB-C or USB-A to Micro-USB cables are common.
Device Specifications: Check the input specifications of the power bank you are charging. Most modern power banks are designed to handle standard USB power inputs.
Potential Downsides and Inefficiencies
While convenient, charging a power bank with another power bank isn’t perfectly efficient. There are energy losses involved in this process, meaning you won’t get a full 1:1 charge.
Energy Loss: Every time energy is transferred, some is lost as heat due to internal resistance in the batteries and charging circuitry. This is a fundamental aspect of electrical engineering.
Charging Speed: The charging speed might be slower than plugging directly into a wall adapter, especially if the source power bank has a lower output current.
Wear and Tear: Repeatedly charging and discharging batteries can contribute to their overall wear and tear, potentially reducing their lifespan slightly over time.
How to Properly Charge a Power Bank With Another Power Bank: A Step-by-Step Guide
Follow these simple steps to safely and effectively charge one power bank from another, ensuring you maximize your portable power reserves when you’re away from an outlet.
Here’s how to execute the power bank-to-power bank charge:
1. Identify Ports: Locate the output port (where you’d normally plug in your phone) on the first power bank and the input port (where you’d normally plug in a charger) on the second power bank.
2. Choose the Right Cable: Use a reliable USB cable. A USB-A to USB-C cable is common for modern devices, but USB-A to Micro-USB also works for older models.
3. Connect the Cable: Plug one end of the cable into the output port of the first power bank and the other end into the input port of the second power bank.
4. Initiate Charging: The second power bank should begin charging automatically. Some power banks may require you to press a button to start the charging process.
5. Monitor Progress: Keep an eye on the charging indicator lights on the second power bank to see its progress.
Can All Power Banks Charge Other Power Banks?
Most modern power banks can be charged by another power bank, especially those with USB-C input ports that support Power Delivery (PD). However, older or very basic models might have limitations or slower charging speeds.
The compatibility often depends on the charging protocols and power output capabilities of both devices.
USB-C PD: Power banks with USB-C Power Delivery (PD) are generally more versatile and can often accept higher charging speeds from other PD-capable devices.
Older Models: Some older power banks might only support slower charging via standard USB-A inputs, meaning they’ll take longer to charge from another power bank.
Manufacturer Guidelines: While not always strictly enforced, some manufacturers might advise against charging their power banks with other power banks, though this is rare.
The Concept of Pass-Through Charging
Pass-through charging allows a power bank to be charged while simultaneously charging another device. Not all power banks support this feature, and it can sometimes generate more heat.
This is a slightly different but related concept. Pass-through charging means you can plug your power bank into a wall outlet (or another power source) and also have a device plugged into the power bank, all at the same time. The power bank essentially acts as a hub.
How it works: Power flows from the source, through the power bank, and to your device. The power bank also draws some power to recharge its own battery.
Benefits: Extremely useful when you only have one outlet available.
Considerations: It can generate more heat, and not all power banks are designed for safe pass-through charging. Always check the manufacturer’s specifications.
When is Charging a Power Bank With Another Power Bank Most Useful?
This technique is invaluable during travel, camping, long commutes, or any situation where access to wall outlets is limited, ensuring your essential devices remain powered.
Imagine these scenarios:
Long Flights/Train Journeys: You’ve used your primary power bank for your phone, but it’s also running low. You have a second, smaller power bank. Now you can top up the first one.
Camping or Outdoor Adventures: When you’re miles from civilization, every bit of power counts. Charging a power bank from another allows you to extend your power reserves for devices like GPS, cameras, or even satellite communicators.
Power Outages: During a blackout, wall outlets are useless. Having multiple power banks means you can keep essential communication devices alive by strategically recharging them.
Busy Airports or Cafes: Outlets are often scarce. You can use your laptop’s power bank to charge your phone’s power bank, ensuring you have enough juice for your devices throughout your travels.
Maximizing Power Bank Efficiency: Tips and Tricks
To get the most out of charging a power bank with another, use high-capacity power banks, charge them when fully depleted, and consider the ambient temperature for optimal performance.
Here are some tips to make the process as efficient as possible:
Use High-Capacity Source: If possible, use a higher-capacity power bank as the source to charge a lower-capacity one. This generally leads to better overall power transfer.
Charge When Depleted: For optimal battery health and efficiency, it’s often best to charge power banks when they are nearly or completely depleted.
Avoid Extreme Temperatures: Both extreme heat and cold can affect battery performance and charging efficiency. Try to charge in a moderate environment.
Use Original or Certified Cables: As mentioned, using quality cables is crucial for safety and efficiency.
Comparing Power Bank Capacities and Charging Times
Understanding power bank capacities (mAh) and input/output ratings helps estimate charging times. A larger capacity power bank will take longer to charge, and a lower input rating on the charged power bank will slow the process.
Let’s look at an example.
| Power Bank Model | Capacity (mAh) | Input Rating (USB-C PD) | Output Rating (USB-A) |
| :————— | :————- | :———————- | :——————– |
| Power Bank A | 20,000 | 18W | 18W |
| Power Bank B | 10,000 | 12W | 15W |
If you’re charging Power Bank B (10,000 mAh) from Power Bank A (20,000 mAh), assuming Power Bank B’s input is limited by Power Bank A’s output at 18W, and considering charging inefficiencies (roughly 20-30%), the charging time will be longer than if you were charging Power Bank B from a dedicated 18W wall charger.
A rough estimate for charging Power Bank B from Power Bank A might look like this:
Theoretical Time: (10,000 mAh / 18W) 3.7V (typical battery voltage) ≈ 2 hours.
Realistic Time (with inefficiencies): Likely 2.5 to 3 hours, possibly longer depending on the exact charging circuitry of both devices.
This highlights that while possible, direct charging from a wall adapter is often faster.
Can a Power Bank Charge a Power Bank That’s Already Charging Another Device? (Pass-Through Charging Deep Dive)
Yes, some power banks support pass-through charging, allowing them to be recharged while simultaneously powering another device. This is a highly convenient feature, but it’s important to ensure your power bank model supports it safely.
This is the ultimate power-saving maneuver. If your power bank supports pass-through charging, you can plug it into the wall (or even into another power bank if that one supports pass-through), and then plug your phone into the power bank. It’s like having a portable surge protector and charger all in one.
Check Specifications: Always look for “pass-through charging” or “simultaneous charging” in the product description or manual.
Heat Generation: Be mindful that pass-through charging can generate more heat. Ensure the power bank has adequate ventilation and doesn’t feel excessively hot.
Not Universal: Many budget or older power banks do not support this feature and could be damaged if you attempt it.
Troubleshooting Common Issues
If you’re having trouble charging a power bank with another, check your cables, ensure the power bank you’re charging is compatible, and confirm that the source power bank is sufficiently charged.
Encountering problems is part of the tech experience. Here are some common issues and how to fix them:
Not Charging:
Check Cables: Try a different USB cable.
Check Ports: Ensure the cable is fully inserted into both ports.
Source Power Bank: Make sure the first power bank has enough charge to supply power.
Compatibility: Though rare, some very old or specialized power banks might not be compatible.
Slow Charging:
Lower Output: The source power bank might have a lower output current than a wall charger.
Cable Quality: A thinner or longer cable can reduce charging speed.
Power Bank Gets Too Hot:
Discontinue Use: If a power bank becomes excessively hot, disconnect it immediately and consult the manufacturer. This can indicate a fault.
When to Avoid Charging a Power Bank With Another Power Bank
Avoid charging a power bank with another if either device is damaged, if you’re using questionable cables, or if the power bank you’re charging has very old or incompatible charging technology.
While generally safe, there are times when it’s best to stick to a wall outlet:
Damaged Devices: Never use a power bank that is physically damaged, swollen, or leaking.
Unreliable Cables: Avoid using frayed, damaged, or unbranded/unknown USB cables.
Very Old Technology: If you have an ancient power bank with very specific charging requirements, it might be safer to use its original charger.
The Future of Portable Power: Innovations to Watch
The evolution of power banks includes faster charging technologies like GaN, increased capacities, and even solar integration, promising more efficient and versatile charging solutions.
The world of portable power is constantly innovating. We’re seeing:
GaN Technology: Gallium Nitride (GaN) chargers are becoming more common, allowing for smaller, more efficient, and faster charging.
Higher Wattages: Input and output wattages are increasing, meaning power banks can be charged faster and charge devices quicker.
Smart Features: Some power banks now come with companion apps to monitor battery health and charging status.
These advancements will likely make charging power banks with other power banks even more efficient and practical.
Frequently Asked Questions (FAQ)
Can I charge my phone while charging a power bank from another power bank?
Yes, if the primary power bank you are using to charge the second power bank also supports “pass-through charging.” This allows it to receive power and deliver power simultaneously.
Will charging a power bank with another power bank damage them?
Generally, no, if done correctly with compatible devices and quality cables. However, using damaged equipment or incompatible charging protocols could potentially cause harm.
How long does it take to charge a power bank with another power bank?
This varies greatly. It depends on the capacity of the power bank being charged, the output power of the source power bank, and the charging efficiency. Expect it to take longer than charging directly from a wall adapter.
Is it more efficient to charge a power bank with a wall adapter or another power bank?
Charging with a wall adapter is almost always more efficient. Energy is lost as heat during every power transfer, so daisy-chaining introduces additional losses.
What is the difference between charging a power bank and pass-through charging?
Charging a power bank means replenishing its battery. Pass-through charging means the power bank is being recharged while it is also charging another device.
Can I use any USB cable to charge a power bank with another power bank?
It’s best to use a high-quality USB cable that is rated for the power output. Cheap or damaged cables can lead to slow charging, overheating, or even damage to the devices.
Conclusion: Embrace the Power Bank Hack
Ultimately, yes, you absolutely can charge a power bank with a power bank. This essential genius move offers incredible flexibility when you’re away from power outlets, ensuring your devices stay juiced up no matter where life takes you.
So, the next time you find yourself with two power banks and a single low battery notification, don’t despair! You have the power to extend your power. By understanding the simple steps, the inherent inefficiencies, and the safety precautions, you can confidently use one power bank to charge another. It’s a smart, practical solution that’s become a staple for travelers, outdoor enthusiasts, and anyone who relies heavily on their gadgets. Keep a good quality USB cable handy, and you’ll always have a backup plan for your backup power.
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Belayet Hossain is a Senior Systems Analyst and Web Infrastructure Expert with a Master’s in Computer Science & Engineering (CSE). Specializing in the “Meta” of the digital world, he applies his engineering background to rigorously test hosting services, domain strategies, and enterprise tech stacks. Belayet translates technical specs into actionable business intelligence. Connect with Belayet Hossain on Facebook, Twitter, or read more about Belayet Hossain.