Best Power Bank for S21 Ultra: Top Picks for Fast Charging

1. Ultra

When I first unboxed this 10000mAh mini power bank, I was struck by its incredibly compact size. It’s genuinely small enough to slip into a coin pocket, which is a huge plus for portability. The matte finish feels nice in the hand and doesn’t attract fingerprints too readily.

Charging my S21 Ultra was a smooth experience, providing a couple of full charges which is more than adequate for a day trip. The LED indicator lights are simple and effective, giving a clear idea of the remaining power. However, I found the charging speed to be just average; it’s not the fastest option out there if you’re in a rush.

This power bank is ideal for casual users who prioritize size and weight above all else. If you need to top up your phone occasionally throughout the day and want something that won’t weigh down your bag, this is a solid choice. It’s not for power users who need to rapidly charge multiple devices simultaneously.

2. Portable Charger, 10000mah Ultra Mini Portable Charger Power Bank With

The INIU 45W power bank immediately impressed me with its build quality; it feels robust and well-constructed, with a textured grip that prevents accidental slips. The “40% smaller” claim holds true, making it significantly more pocketable than many other 10000mAh options I’ve tested.

I found the 45W fast charging capability to be a real benefit. It juices up my S21 Ultra noticeably quicker than standard chargers, which is invaluable when I’m on the go and need a significant power boost in a short amount of time. The dual USB-C ports are also a welcome addition, allowing for simultaneous charging of two devices.

This power bank is a fantastic option for those who demand speed and a compact form factor. It’s perfect for business travelers or anyone who frequently finds themselves needing to quickly recharge their devices. However, the slightly higher price point might deter budget-conscious buyers.

3. Iniu 45w Fast Charging Portable Charger, 40% Smaller 10000mah With

This INIU 45W power bank is a strong contender for the best power bank for S21 Ultra, especially if fast charging and portability are high on your list. Its compact design, touted as 40% smaller, makes it a breeze to carry around without adding bulk. The matte black finish looks sleek and resists smudges quite well.

During testing, the 45W output significantly reduced the time it took to get my S21 Ultra back to a usable charge level. It’s comforting to know I can get a substantial amount of power in just a short break. The build quality feels premium, with no creaky plastic or loose parts, and the LED indicators are bright and easy to read.

A minor annoyance I noticed is that while it’s smaller, it’s still a bit thicker than I’d ideally prefer for a truly pocketable device. It’s not a dealbreaker, but it’s something to consider if absolute slimness is your top priority. This is ideal for someone who needs a reliable, fast-charging solution on the go without sacrificing too much pocket space.

4. Iniu 45w Fast Charging Portable Charger, 40% Smaller 10000mah With

The INIU 20000mAh power bank is a powerhouse, and its “ultra compact” claim for its capacity is quite accurate. It feels solid and well-built, with a comfortable, textured surface that provides a good grip. The dual USB-C ports are strategically placed, making it easy to connect devices without them getting in each other’s way.

I was particularly impressed with the 65W PD output, which not only charges my S21 Ultra at lightning speed but can also handle my laptop, a significant advantage for travelers. It provides multiple full charges for my phone, and the ability to power larger devices means fewer compromises when I’m away from an outlet. The LED display showing the exact percentage is a much-appreciated upgrade over simple indicator lights.

However, the sheer capacity means it’s not the lightest option available, and it takes a considerable amount of time to recharge the power bank itself. This is a fantastic choice for heavy users, digital nomads, or anyone who needs to keep multiple devices, including laptops, powered up for extended periods. If you only need to charge your phone a couple of times, this might be overkill.

6. Mini Portable Charger 5000mah Power Bank, 15w Pd USB C

When looking for a compact power boost for my Samsung S21 Ultra, this 5000mAh unit caught my eye. Its diminutive size makes it incredibly easy to slip into a pocket or a small clutch, which is a huge plus for those days when I’m traveling light. The 15W PD output is respectable, offering a decent charge speed, though not the fastest available for the S21 Ultra.

I found the build quality to be solid enough, with a smooth, matte finish that felt good in hand. It’s definitely designed for portability, and it excels at that. However, the 5000mAh capacity means it won’t fully recharge an S21 Ultra more than once, so it’s more of a top-up solution than a complete lifeline.

This power bank is ideal for someone who prioritizes minimal bulk and just needs to extend their phone’s battery life for a few extra hours. Think of a quick business trip where you’ll have access to outlets but want peace of mind, or a long day out where you’re primarily using your phone for navigation and photos but won’t be draining it completely.

The USB-C port handles both input and output, which simplifies things considerably. While it’s a convenient little charger, the charging speed, while adequate, isn’t going to impress power users. If you’re constantly on the go and need rapid charging, you might find this a bit slow.

7. Iniu 20000mah Power Bank, Small 45w Pd Fast Charging Portable

The INIU 20000mAh power bank is a serious contender for the best power bank for S21 Ultra, especially if you demand substantial capacity and fast charging. Its 45W PD output is impressive, delivering a rapid charge that noticeably juices up the S21 Ultra quickly. I was able to get a significant percentage of charge in a short amount of time, which is crucial when I’m in a pinch.

Despite its large 20000mAh capacity, INIU has managed to keep the size relatively manageable, though it’s certainly not pocket-friendly. The matte finish feels premium and provides a good grip, preventing accidental slips. The multiple ports are also a welcome addition, allowing me to charge other devices simultaneously.

This power bank is perfect for extended trips, camping, or for anyone who uses their S21 Ultra heavily throughout the day and needs multiple full charges. It’s the kind of device you can rely on for a weekend away without needing to find a wall socket. I found myself less anxious about battery life when using this.

One minor annoyance I noticed is the weight; while not excessive for its capacity, it’s definitely noticeable in a bag. Also, the textured surface, while grippy, can attract dust and lint over time, requiring occasional cleaning. Overall, it’s a robust and reliable option.

8. 25w Super Fast Charging Portable Charger Power Bank with Built

This 25W Super Fast Charging power bank offers a solid balance between speed and capacity for the S21 Ultra. The 25W output is a sweet spot, providing a substantial charge without being overly aggressive on battery health. I appreciated how quickly it topped up my phone, making it useful for quick boosts between meetings or during commutes.

The design is fairly standard, with a smooth, slightly glossy finish that looks decent but can be a fingerprint magnet. The unit feels sturdy and well-constructed, giving me confidence in its durability. It’s not the smallest power bank, but it’s not excessively bulky either, fitting comfortably in my backpack.

This power bank is a great choice for the everyday user who needs more than a single charge but doesn’t require the immense capacity of a 20000mAh unit. If you’re a moderate user who finds yourself needing a top-up by late afternoon, this will serve you well. It’s also good for short trips where you might not have consistent access to power.

One aspect that could be improved is the inclusion of a built-in cable or a more integrated design; having a separate cable to carry, while common, always feels like one more thing to manage. The charging speed is good, but it’s not the absolute fastest available for the S21 Ultra, which some users might seek.

9. Portable Charger,Ultra Slim 10000mah 22.5w Power Bank,USB C In/output Fast

The “Ultra Slim” moniker for this 10000mAh power bank definitely holds true; it’s remarkably thin and lightweight, making it a pleasure to carry. The 22.5W output is quick enough for the S21 Ultra, offering a noticeable speed boost compared to older, slower chargers. I found it easy to forget I was even carrying it, which is a testament to its design.

Its slim profile is its strongest suit, easily sliding into the tightest pockets or the front pouch of a laptop bag. The build feels solid, with a matte finish that resists minor scratches and smudges. The USB-C in/out functionality is convenient, simplifying the charging process for both the power bank and my phone.

This power bank is ideal for the minimalist traveler or the everyday user who wants a substantial charge without adding significant bulk. If you find yourself needing one full recharge and a bit extra throughout the day, this is an excellent option. It’s perfect for those who value portability above all else.

However, the slim design means it does get noticeably warm during fast charging, which, while not alarming, is something I paid attention to. Also, the 10000mAh capacity, while good, won’t provide multiple full charges for the S21 Ultra, so heavy users might need something larger. It’s a trade-off for that sleek form factor.

10. Magnetic Portable Charger, 22.5w Power Bank Fast Charging 10000mah, Portable

This magnetic portable charger offers a convenient way to keep the S21 Ultra powered up, especially with its 22.5W fast charging capabilities. The magnetic attachment is surprisingly strong, snapping securely onto the back of the phone and allowing for charging on the go without cables. I found this incredibly useful for staying connected while walking or multitasking.

The 10000mAh capacity provides a good amount of extra juice, enough for a substantial top-up or nearly a full charge. The unit itself feels well-built, with a smooth, premium finish that complements the phone’s design. Its portability is excellent, and the magnetic feature adds a layer of practicality that cable-based chargers lack.

This power bank is perfect for users who appreciate the convenience of wireless charging but want more capacity than a standard Qi pad. If you often find yourself needing to charge your S21 Ultra while moving around, or want a quick, cable-free boost, this is a fantastic option. It’s ideal for those who value streamlined usage.

My main critique is that the magnetic attachment, while strong, can add a bit of bulk and weight to the phone, making it feel slightly less comfortable to hold for extended periods. Additionally, while 22.5W is fast, it’s not the absolute quickest charging speed available for the S21 Ultra, which might be a consideration for some.