If your smartphone doesn’t have enough juice to last the entire day, you might find yourself having to charge it up frequently, relying on either the main charger or a power bank. Battery cases offer a convenient solution to this problem, you can think of it as adding a second battery to your smartphone which will, in turn, extend your smartphone’s runtime.

Battery cases are similar in many ways to a traditional power bank, except they take the form of a case which stays attached to your phone. The advantage of battery cases is that you never need to worry about bringing a power bank - it’s already attached to your smartphone. Furthermore, most battery cases offer charging pass-through which charges both the battery case and your smartphone’s battery.

One significant downside of battery cases is that they often add a lot of thickness to your smartphone, whether you decide to use them or not. The battery capacity will vary depending on the model you buy, but typically you’ll get at least one full charge to your smartphone. Remember to check the mAh rating of the battery and compare it to the mAh rating of your smartphone.

What you need to look for when buying a battery case

In my opinion, it’s very important to buy from a reputable brand when you’re in the market for a battery case. Lithium batteries are, by nature, limited in capacity and they degrade over time. The rate at which lithium batteries degrade is somewhat dependant on the quality of the product, so if you want to have a long-lasting battery case, then my recommendation is to buy from a brand which has a reputation for high-quality products.

In addition to buying from a reputable brand, it’s also important to look at the capacity of the battery case. A battery case which has a similar or higher capacity to that of the battery in your smartphone should be able to fully recharge your smartphone from 0 to 100% in one go. If you are unsure of the capacity of your smartphone battery, have a look on gsmarena.com. Most modern smartphones have a capacity in the region of 2000 - 3000 mAh.

Battery cases for iPhones

Apple Smart Battery Case

The Apple Smart Battery Case sells for £99.00 straight from Apple, which is the most expensive battery case on this list. If you’re buying a Smart Battery Case for your iPhone, it’s not because it’s reasonably priced or high in capacity, it’s because the product has been expertly crafted to around the iPhone. If you’re wondering what’s so ‘smart’ about this battery case, it’s the only battery case that communicates directly with iOS. The tight software integration allows your iPhone to show the remaining charge of both batteries, right on your screen.

The Apple Smart Battery Case is only available for the iPhone 6, 6S and 7, which makes sense because these are the iPhone models with smaller batteries, hence they suffer from shorter battery life. £100 is a significant amount to spend on a battery case, but if you appreciate the design of your smartphone and the ‘smart’ integration with iOS, you won’t be disappointed.

Mophie Juice Pack for iPhone

The price of a Mophie Juice Pack varies between £20 and £90, depending on the product and how new your iPhone is, so there’s something for everyone’s budget. Juice Packs are available for all iPhones from the iPhone 5 all the way up to the iPhone X. Mophie are a top brand, well known for their battery cases - some of their products are even sold in the Apple store.

Juice Packs fit iPhones very well, and they typically offer high battery capacities so you can keep using your iPhone for longer. Depending on the specific product you opt for, you may also get added drop protection.

Anker PowerCore Case

Anker are well known for manufacturing high-quality power banks at competitive prices, now they have branched out into battery cases. The Anker PowerCore Case costs a reasonable £30 on Amazon and holds a modest 2200 mAh battery - enough to top up your battery by 80%.

Anker have taken a one-size-fits-many approach, so the PowerCore Case will fit any iPhone 6, 6S or 7. Unfortunately, this has taken a toll on the design, as the case requires a short cable to plug into the bottom of your iPhone when charging. On the bright side, this could be considered an advantage over other battery cases because you don’t need to take the case off to plug your iPhone into a computer.

Battery cases for Android Smartphones

Mophie Juice Pack for Samsung Galaxy

In addition to selling battery cases for iPhones, Mophie also sell battery cases for Samsung Galaxy smartphones - one of the most popular choices in the Android market. Mophie’s Juice Pack line of battery cases are available for the Samsung Galaxy S7, S7 Edge, S8, S8+, Note 8, S9 and S9+. As with Mophie’s iPhone battery cases, prices vary immensely, typically with the newer models being more expensive.

Mophie’s battery cases for the Galaxy lineup stand out, not least because they’re from a trusted brand name, but because they offer comparatively high battery capacities, often 3000 mAh or more. Furthermore, the battery cases have full support for Wireless Charging, so there is no need to remove the battery case to access this functionality.

Anker PowerCore Slim 5000

While this isn’t technically a battery case, it’s designed to be used in a similar way. As the name suggests, the PowerCore Slim 5000 has a slim design and a silicone surface which allows it to grip against the back of your phone without the hassle of most bulky power banks. Don’t be fooled by the photo, this power bank can be used with any smartphone, and the 5000 mAh capacity is quite generous too.

I think the Anker PowerCore Slim 5000 is a great choice if you are using a smartphone for which battery cases aren’t available, or if you don’t want to have a battery case connected to your smartphone 24/7. Furthermore, the £21 price tag is very affordable compared to many other high-end battery cases.

Summary

Whether or not you buy one of the battery cases listed above, there are, in my opinion, 5 important things to keep in mind when buying a battery case:

1. Buy from a reputable manufacturer, so you don’t get a dodgy battery.

2. Be prepared to spend more for a higher quality product.

3. Check the battery capacity and compare it to your smartphone’s battery.

4. Check how well the case fits.

5. Consider whether you really need a battery case, or whether a power bank will suffice for your needs. If your smartphone is suffering from poor battery life, it’s always worth trying a factory reset, as this will sometimes fix the issue.