What is a Power Bank? How do Power Banks work?

How do Apple Watch power banks work?

Today’s society is driven by technology. From mobiles, tablets, and laptops, to portable speakers, GoPros, drones, and more. We’re always connected. Or at least we always want to be connected. Until the unimaginable happens and our battery runs out. Just as you’re about to post that beautiful sunset photo during prime Instagram engagement hours. There’s nothing worse. Unless you have a power bank at hand to save the day.


What is a power bank?

What is a power bank?Power banks are portable battery charging devices that are designed to be used on the go. Think of them as the new and improved version of the ‘rechargeable battery’ that used to come with an accompanying charging dock. For a short time, they appeared everywhere. And aimed to replace the single-use battery.

The modern-day power bank works a little differently. Storing electrical energy inside the ‘bank’ to use as and when it’s needed. The charger sits inside a specially designed case and has a circuit breaker to control the power flow. This ensures the energy or ‘charge’ isn’t drained. Allowing you to use the power bank as a spare battery back-up when your device is running low and you aren’t in reach of a plug socket to recharge your device.


How does the power bank work?

Power banks are portable device charges, specifically designed for when you’re on the move. The built-in-power bank sits inside a case and has a special circuit located inside to control the power flow. This smart technology will only charge your battery when it needs to be charged, saving power and ensuring your device never becomes overcharged. Power banks are also referred to as battery banks, battery packs, fuel banks or power stations, to name but a few.


Inside a battery pack power bank

How do I use a power bank?

Power banks are compatible with any device that can be plugged into a USB port. Take the iPhone charger, for example, one end can be inserted into a USB port, while the other end inserts directly into the iPhone, making it perfectly compatible with the power bank. Power banks work by producing power through a USB port, via built-in Lithium-ion batteries, and can juice up multiple devices that have run out of battery. They can also be recharged via the same USB port, meaning they are reusable time and time again.


What can a power bank charge?

Almost anything that can be charged using a USB cable that’s connected to a device can be charged by a power bank. Think smartphones, the Apple Watch, drones, portable speakers, cameras, MP3 players, GoPros, GPS systems, iPads, and even some tablets. The list goes on. Just don’t forget to keep your power bank fully charged too.


Power bank charging phone

How many times can a power bank charge my phone?

The answer to this question is not as straightforward as the question. The number of charges depends on several factors, such as the device you’re charging; what you’re doing while the device is being charged; and, how old and the level of charge the power bank has. Generally speaking, you can use the following formula to help you figure it out: 

(power bank capacity x 3.7 / output voltage)
x 0.85 / phone battery capacity 
Total number of recharges

Let's use the formula above to calculate the number of charges a 5000 mAh power bank with 5V output voltage will give the iPhone X with 2,716 mAh battery capacity:

(5000 mAh x 3.7 / 5V) x 0.85 / 2716 mAh = 1.15 charges


How do I charge/recharge a power bank?

More often than not, power banks receive their charging power through a dedicated input socket. Due to the power supply and available current, the fastest charging route is when it’s plugged into a socket adapter on the wall. But it can also be charged by inserting the charging cable into the USB socket of your home computer or laptop. Some TVs also have USB ports which you can connect your cable to and charge your power bank.


How long does it take to charge a power bank?

The length of time it takes to charge is dependent on the current charge level as well as the power bank’s capacity. For example, if the power bank is already 70% charged, it will take a lot less time to recharge than if it was running on empty. For larger banks, it can take up to 2x, 3x or even 4x longer times to recharge. Unless you have a high-speed charger, which restores battery capacity a lot faster than a standard power bank. Most power banks will also notify you when they’re fully charged by displaying a percentage or LED light indicator.


The value of power banks

Power banks have become invaluable and even more popular over the last few years. With the ever-increasing demand to always be online and stay connected. Especially when it comes to doing business. The days of taking hours to respond to an email or missing a deadline due to being offline are well and truly over. Modern-day battery life does not help us at all with these expectations. This can be a real struggle for anyone, especially business travelers, who spend a lot of time going from meeting to meeting or up in the air.

Why Sumato WatchBox power bank?

Apple Watch charging case with Power BankThe Sumato WatchBox is the first charging case for Apple Watch with a built-in power bank. The stunning design offers a lot more than meets the eye. Just like your everyday power bank, the Sumato WatchBox gives you the freedom to live your life, but on your terms. This means you’re never stuck waiting next to a static power source while your Apple Watch is charging.


Stop running on empty

Aside from charging your Apple Watch, the Sumato WatchBox doubles up as a ‘normal’ power bank. Allowing you to charge your device - as well as anything else you may need to recharge - at any time, in any place.


How many times can Sumato WatchBox charge my device?

Here is the formula again:

(Power bank capacity x 3.7 / Output voltage)
x 0.85 / Phone battery capacity 
= Total number of recharges

Using this formula see table below for most popular Apple and Samsung devices:

Device mAh Charges
iPhone XS Max 3,174 10.5x
iPhone XR 2,942 1.1x
iPhone XS 2,658 1.2x
iPhone X 2,716 1.2x
iPhone 8 Plus 2,691 1.2x
iPhone 8 1,821 1.7x
iPhone 7 Plus 2,900 1.1x
iPhone 7  1,960 1.6x
iPhone 6S Plus 2,750 1.1x
iPhone 6S 1,715 1.8x
Samsung S9/S8 Plus 3,500 0.9x
Samsung S9/S8 3,000 1x
iPad 8,600 0.4x


Another (not so secret) benefit of the Sumato WatchBox

One of the most talked about features of the Sumato WatchBox? Its ability to charge your Apple Watch inside the box while you’re on the move. Something a standard power bank wouldn’t allow you to do due to its design.


Sumato WatchBox key facts

Magnetic Apple Watch chargerThe Sumato WatchBox provides up to 10x charges for your Apple Watch. It also doubles up as an iPhone and iPad charger, providing 1x and 1/2x charges respectively.

The Sumato WatchBox also comes with:

  • 5000 mAh built-in power bank
  • Removable 500 mAh power bank with portable keychain
  • MFI certified storage box, built to last from aircraft grade aluminium
  • Embedded magnetic Apple Watch charging station

With the Sumato WatchBox power bank, there’s no waiting around. The clean, cable-free environment means it’s ready to use straight out of the box. It’s extremely functional and complements Apple Watch’s flawless design, making it the perfect solution for anyone on the go.


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