Review: Anker 521 Magnetic Battery
The Anker 521 magnetic battery was one of the first power banks to support the new MagSafe feature of the iPhone. It enables you to magnetically attach the power bank to the back of your MagSafe compatible iPhone and charge it wirelessly on the go without cables.
Fittingly, Anker originally called this power bank a snap and go power bank but changed the naming convention. It’s now called a MagGo power bank.
Though the iPhone 13 Pro Max has a powerful battery, I rarely make it through an entire day on a single charge. Probably, because I do a lot of photo editing on my iPhone.
So when Apple announced MagSafe, I hoped that either Apple or someone else would release a power bank that I could attach magnetically and without cables to my iPhone. A few months later, Anker was one of the first to release such a magnetic and wireless power bank.
In this Anker 521 magnetic battery review, I’ll share my real-world experience using it.
Models of the Anker Magnetic Battery
Since Anker released the original PowerCore Magnetic 5K in 2021, they released three more models and changed their products’ naming convention.
- The original model I used for this review was called Anker PowerCore Magnetic 5K. It’s now called Anker 521 Magnetic Battery.
- In Mid 2022, Anker released the successor of the Anker 521 MagGo: The Anker 621 magnetic battery. It’s slightly thinner than the original Anker 521 and offers the same capacity as the Anker 521.
- Another MagGo model is the Anker 622 Magnetic Battery. It also has a capacity of 5.000 mAh but comes with a stand attached to the power bank.
- Anker also released a 10.000 mAh version called Anker 633 Magnetic Battery. This version is slightly larger (and thicker) than the 5.000 mAh models.
To help you decide which Anker MagGo Magnetic battery model is suitable for you, here’s a capacity, size and weight comparison of the Anker magnetic batteries 521 vs 621 vs 622 vs 633. Measurements are in inches and pounds.
If you’re looking for a lightweight and small magnetic power bank with a capacity of 5.000 mAh, then go for the Anker (621) magnetic battery (the successor of the Anker 521). If you’re looking for more charges at the price of weight and size, then go for the Anker 633 magnetic power bank.
Please mind that this review is about the Anker 521 magnetic battery that was originally called Anker PowerCore Magnetic 5K. I’ve added info about the other models for completeness.
Why I bought the Anker 521 magnetic battery
As mentioned above, I rarely make it through the day with a single charge on my iPhone.
As I’m a Minimalist, I always strive to get rid of things, especially things, that I need to carry and that would prevent me from traveling light.
Eliminating the cables for everyday charging was the reason I originally switched from my Anker 10.000 mAh slim power bank to the Apple Smart Battery Case for an everyday use power bank.
And that was also the reason why I bought the Anker 521 magnetic battery: To be able to charge my iPhone on the go without using cables. like this:
How we tested
We tested each battery’s capacity by fully charging it very slowly via a 5V/1A USB-A charger. We followed this 5W charging protocol, instead of a much faster charge that most of the packs support, for two reasons:
- To simulate the kind of output you’d get from a portable solar panel
- The slower you charge a Li-Ion battery, the more it stores
When each battery was fully charged, we then fully drained it by plugging it into a USB load tester set to draw a constant 2 amps. In between the load tester and the charger we placed a data-logging USB multimeter that let us record power, voltage, and total energy draw numbers.
After the “lab” testing, we also paired the packs with a small Renogy 10W solar charger to measure how things worked in a real-world scenario. This happened on clear, sunny days (irradiance levels were between 575W/m2 and 750W/m2). A data logging USB multimeter captured a picture of each device’s charging session. That way, we could verify that each pack holds a stable power draw on the panel and will work in conjunction with the smallest panel we recommend.
We also plugged all of the winners into a partially charged iPhone XS Max and a Samsung Galaxy 8, with the multimeter in the loop to monitor charging activity, just to confirm that the packs work normally with modern phones.
For the three packs in this review that are marketed as waterproof and claim an IP67 rating, we charged them and then submerged them in a few inches of water for 2 minutes. Then we dried them off and let them sit for an hour before plugging them into our testing apparatus in order to confirm they could still handle a 5V/2A test load.
Note that we did not test USB-C PD ports, or any type of quick-charging protocol support, since, again, we’re not interested in fast charging. Slower is better, and while fast charging is nice to have, it’s not a priority for this application so we didn’t invest time in testing it.
Why you should consider carrying two battery packs
When selecting a Li-Ion power bank for emergencies, always carry the most battery capacity you can fit within your weight budget. energy storage capacity means:
- Longer lifespan, since you’re doing fewer charge/discharge cycles for the same amount of power drawn from the device.
- real-world capacity, because a larger bank will drain to zero more slowly (for a fixed current draw) than a smaller one, and the slower you drain your bank the more charge you get out of it.
- You can capture more charge when you get the chance, either from solar panels, a wall socket, or a larger battery.
- Better odds that you’ll have power when you need it.
Based on current 2019-2020 tech, the best approach for preppers is to carry two 10,000mAh packs, instead of giant 20,000mAh pack. The reasons are compelling:
- “Two is one, and one is none.” This core preparedness mantra speaks to the importance of having a backup of critical gear. Any kind of redundancy you can build into your preps (without sacrificing in other areas) gives you a powerful advantage in any emergency
- Nearly all the packs in this review are really repackaged collections of 18650 batteries, and since they all use basically the same battery tech and format under the hood, then carrying 20,000mAh means carrying six of these batteries. You can carry six of them in one pack, or you can carry six in two separate smaller packs, but you’re still carrying the same number 18650’s at about the same total weight and charge.
- The packs can have different port formats and features, giving you more options. You might picking pack that’s micro USB and USB-A, and another that’s USB-C and USB-A. Or, if you go with our two main picks, you’ll get one pack that’s waterproof and has a light, and another that can quick-charge some types of supported devices.
Deeper notes on testing and reading results
Skip this section if you don’t want nerd-level details.
Reading the voltage numbers
The 18650 lithium-ion batteries that make up the guts of almost all the chargers in this review operate at around 3.7V, depending on the amount of charge in them. But the USB spec is nominally 5V, though it can work with as little as 4V depending on the flavor and port type. So the Li-Ion-based chargers are running a step-up circuit in between the internal batteries and the USB port.
For a variety of reasons not worth going into here, if you’re trying to fully charge a Li-Ion battery of any type, you’ll want to be able to offer it at least 4.6V throughout the course of the charging cycle. This brings us to the fact that in many of the test runs, you can see from the graphs that the packs’ voltage output dropped to under 4.6V.
That’s ok, though, because if we dial back the 2A load to, say, 1A, the voltage on these under-volted packs rises back up to 4.6V or higher. And under normal usage conditions, any USB device you plug into the pack will figure out how much current it can draw and still get the voltage it needs to fully charge its internal battery. But load testers like the one we used aren’t that Smart — our tester just presents a static, two-amp load, and doesn’t vary it even if it’s not getting good voltage.
Voltage and current fluctuations
While we like to see some stability in the voltage and current output of the pack, we didn’t put a lot of emphasis on this because we mainly just care about the overall number of watt-hours we’re getting from the unit as we discharge it.
In one or two of the packs, there are some variations in voltage that look like the pack was trying to negotiate a charging rate with the load tester, and in others there’s what could be temperature variation (batteries heat up as they charge and discharge). But we ignore these and stay focused on the final watt-hours totals.
Rated vs. measured capacities
Because we used a static load tester, we couldn’t quite wring all the capacity out of the batteries that we could have. In fact, what we’re really measuring is the amount of time you can pull a static 2A out of these packs, and not really the whole capacity. But this is a close enough proxy, and it certainly gives us a baseline for a fair comparison of all the different banks’ relative performance.
The milliamp-hour numbers that we use in the bulk of this review are based on the internal battery’s 3.7V operation, and not the USB port’s 4.5V-5V operation. When we measured the discharge capacity of these banks, we used the final watt-hours numbers and a presumed 3.7V internal battery pack to back into a real-world milliamp-hours number to compare to the rated number. So in our big spreadsheet of batteries, the watt-hours number is measured, and the milliamp-hours number is derived by dividing the watt-hours number by 3.7V.
Discharge rate vs. real-world capacity
The rate at which you drain a battery to zero is called the “C-rate”, and it’s presented as a number like 1C, 3C, 0.5C, etc. This number is the fraction of the battery’s capacity (C) you drained from it in one hour.
Example: For a hypothetical 2 amp-hour battery, if you discharge it completely in one hour (via a current draw of 2A), you’re discharging it at 1C. If you discharge it in two hours via 1A current draw, you’re discharging it at 0.5C.
The discharge rate matters for testing and usage, because the more rapidly you discharge a battery, the less of its rated capacity you actually see. This means that discharging at 10Ah battery via a two-amp load is not quite the same as discharging a 20Ah battery via a two-amp load — the smaller battery will empty out faster, which means we should get a little bit less of the rated charge out of it than if you had discharged it at one amp.
The discharge rate for our tests was 0.2C for the 10Ah packs and 0.1C for the 20Ah packs. A look at Li-Ion voltage vs. discharge curves shows that the performance difference between 0.2C and 0.1C is negligible, and this fits with our observed results. (Once the voltage drops below 3V, you’ve ended the discharge cycle, so the different C-rates reach that point at different discharge percentages.)
At 0.3C and higher rates we were using, we couldn’t find much of a correlation between speed of complete discharge and the degree to which measured capacity matched (or didn’t) rated capacity.
TENWAYS Power Bank
Enjoy extended cycling pleasure with the TENWAYS power bank. It is sleek, lightweight and compatible with all TENWAYS e-bikes.
We currently ship to the European Union (except for Malta and Cyprus). Please note, you will not be able to return the Power Bank. It’s a non-refundable item.
Specifications
- Power Bank
- Dimensions 212×138×57 mm
- Battery Capacity 180 Wh
- Charging Time PD40 W-4.5 h
- Color Sparkly Gray
- Weight /kg 1.25 kg
- Waterproof Bag
- Dimensions 230×150×71 mm
- Material Waterproof composite material
- Assemble Velcro strapping bundle
- Color Black
- Weight /kg 0.2 kg
After connecting to the e-bike, the power bank starts charging the main battery, and the battery can continue to support your ride simultaneously.
You can use the power bank to charge the main battery at any time, just like how you charge your phone with a power bank.
If you do decide to ride your e-bike while charging, we recommend using the power bank when the main battery is above 20%-30% state of charge, for a better riding experience.
Yes! Velcro tape is used on the downtube and seat tube for easy installation. Extension cables are also provided for e-bikes that have charge portals near the top of the downtube.
You won’t need tools or a lot of time, fastening is fast and secure via three velcro straps, two on the down tube and one on the seat tube. Check the short instruction manual for further details.
The power bank has a verified water-resistant design to protect it against the elements. However, in the interest of security, we recommend that you store it indoors.
Each power bank is shipped together with a user manual written in English. The user manuals in German, Dutch, French, Italian, and Spanish can be found below.
Anker 321 Power Bank (PowerCore 5K)
Why We Picked It
A huge battery capacity is convenient, but sometimes you need a small device that you can carry around without a backpack. The 5,200mAh Anker 321 Power Bank fits that need perfectly, especially because it offers both USB-A and USB-C ports.
Who It’s For
This is ideal for people who care more about portability than capacity. It won’t charge your phone multiple times, but it can still get you through a long day.
Best for Charging Laptops
Anker 737 Power Bank
Why We Picked It
The Anker 737 features 140W output, which means it can charge bigger, more power-hungry devices like a laptop just as effortlessly as it can juice up a phone or tablet.
Who It’s For
If you often need to charge a laptop when you’re nowhere near an outlet, this 24,000mAh backup battery can lower your stress levels. It’s more expensive than other options on this list, so people who tend to charge smaller devices like phones or tablets are better off with the more affordable choices.
Best High-Capacity Power Bank
Otterbox Fast Charger Power Bank
Why We Picked It
Many people know Otterbox for its durable phone cases, but the company is now bringing that expertise to the world of power banks. In addition to its strong build quality, the Otterbox Fast Charger Power Bank has all the key features you need, such as fast charging with PD, both types of USB ports, and several options for battery capacity.
Who It’s For
If you are worried about damaging your backup battery when you travel or commute, this is one of the safest bets. It also comes with a limited lifetime warranty.
Best Solar-Powered Portable Charger
What Size Battery Do You Need?
These days small portable batteries have a capacity of around 5,000mAh, which means they easily fit into your s and still have enough power to fully top up your phone once.
Meanwhile, a 10,000mAh battery can give today’s flagships two full charges. A 20,000mAh battery can charge a flagship four times, or two phones two times. Some power banks have enough juice to power laptops. Of course, a higher capacity often translates to a heavier, larger, and more expensive battery.
Most companies advertise how many times their products can recharge popular phones, but if you want to calculate that number for yourself, RAVPower has a useful guide (Opens in a new window) that can give you an estimate.
In the end, it’s best to assess your typical needs before buying. If your phone hits the red zone by mid-afternoon and you only need enough juice to get you to the end of the workday, a 5,000mAh battery should be plenty.
FAQ
What capacity power bank do I need?
Don’t fall into the trap of thinking a 3,000mAh power bank will give your 3,000mAh battery smartphone a full charge, and that a 9,000mAh power bank will charge it three times. No portable charger runs at 100% efficiency. In truth, most average between 60- and 70%, with the best-performing models able to reach 80- or 90%. Wireless charging models may be less efficient still.
To work out what capacity bank you need, first check the spec of the device you want to charge to find out its battery capacity, then decide how many times you want to be able to charge it. For a rough estimate, calculate Connected device battery capacity x Number of recharges x 1.6 = Minimum power bank capacity you should look to buy.
As a rule of thumb, a 5,000mAh bank is a single-charge device, 10,000mAh hits the sweet spot between capacity and portability, and you want to look for closer to 20,000mAh for a laptop. We’ve got some of those high-capacity power banks here – just don’t try to stuff any of them in your !
How long does it take to recharge a power bank?
The time required to recharge a power bank will depend on its capacity, what you are using to recharge its battery and whether or not it’s empty.
For the fastest charging you should look to the new breed of power banks that support graphene technology and charge over a DC input (such as the Chargeasap Flash Pro – a 25,000mAh bank that can get to 80% in 45 mins and 100% in 70 mins), but these tend to be pricey.
For mainstream power banks, the fastest you’ll find is a USB-C inout/output that supports Power Delivery. This standard now goes up to a maximum of 240W, but in portable chargers you should expect to find an 18W port. Using such a port, the average 10,000mAh power bank might recharge in 2-3 hours from empty.
The cheapest models still tend to charge over Micro-USB, usually at around 10-12W. Avoid 5W power banks like the plague unless they are very low in capacity or you’re not in a rush.
What is passthrough charging?
Passthrough charging allows you to simultaneously charge devices connected to a power bank and the power bank itself. It’s a very handy solution if you are short on mains power outlets and need to get multiple devices charged up overnight, for example. However, not all power banks support it, so be sure to check the spec of your portable charger before you buy.
How do I know how much power is left in my power bank?
Assuming you know how much capacity it had when full, you can work out how much power remains either through a series of LEDs on the casing (usually activated by plugging in a device to charge or pressing a button on the side), or via the LCD if your power bank supports one. LCDs are preferrable, because they give a more accurate readout, particularly when it comes to higher-capacity power banks.
What are GaN power banks?
GaN is short for gallium nitride. It requires fewer components than traditional silicone chargers, which means power banks that use the technology can be less bulky and more efficient. If portability is your primary concern, then as well as considering the power bank’s capacity you should also look for one that uses GaN.
What charging speed should I look for in a power bank?
The first power banks on to the market ran at 5W, which is the same speed as the original iPhone chargers (aka slllllloooooowwwww). We wouldn’t recommend anything below 10W these days. This speed is known as ‘fast charging’, and it’s still rather common in cheaper models, but it’s not really the fast charging we’ve become accustomed to today. So many of the latest smartphones now support super-fast wired charging, and it seems crazy not to buy a portable charger that supports that top speed if possible.
The standard your phone uses to achieve its top charging speeds is important here. Some have proprietary technologies that work only with accessories manufactured and sold by that company. Some offer fast charging through Quick Charge or Power Delivery. Some support neither Quick Charge nor Power Delivery, but do support protocols such as PPS (Programmable Power Supply) or SCP (Super Charge Protocol). Make sure the portable charger you buy matches the fast charging standard supported by your phone.
The term Power Delivery does not in itself denote a performance rating. It could be capable of delivering anything between 18W and 240W. This is particularly important if you’re looking to charge a USB-C laptop – anything under 30W won’t cut it, many laptops will refuse to play ball below 45W or even 60W, and some larger laptops might require 90W. You will need to check the spec of your laptop to know what speed it requires.
At the other end of the scale, if you need to charge a low-power device such as a smartwatch or a pair of wireless earbuds, look out for a power bank that is certified for low-power devices. Many of those that are not will simply cut out when you try to charge these devices, because they aren’t able to detect a significant drain on the battery.