Once upon a time, it seemed like everybody was buying battery cases for their iPhones to get the extra juice they needed to get through the day. However, the big problem with a battery case is that it makes your phone bulky and heavy, and with phones growing larger and larger, the battery case just doesn't always make as much sense as it once did. In my opinion, an external battery pack is the way to go.

To that end, I've rounded up the best compact batteries out there. Although they cost more, I personally like batteries that have a Lightning cable built into them, so I don't have to worry about carrying around a charging cable. But I've also included some budget picks for those who want to spend as little as possible. And, while we're planning a separate roundup for Android models, anything here without an integrated Lightning cable will work perfectly well with an Android phone (or any other portable gadget), so long as you provide a Micro-USB or USB-C compatible cable.

Note that CNET may get a share of revenue from the sale of the products featured on this page. 

Mophie has discontinued its swanky aluminum-clad PowerStation Mini Plus, which has an integrated "switch-tip" Lightning/Micro-USB cable (an adapter converts the Micro-USB to Lightning). However, it's still an excellent charger that you can find online at a discount and there are even better deals on certified refurbished models (I bought two of the pink ones for less than $10 each, and they seemed perfectly good). The Mini Plus is available in 4,000- and 6,000-mAh versions. The latter is about a third thicker. 

The Hub Mini has integrated Lightning and Micro-USB cables. It's not so slim, but it is compact and easily fits in a pocket. It has a 3,300-mAh battery inside. 

The newest version of Mophie's PowerStation Plus ($80) has a fabric finish and houses a 6,040-mAh battery. Like the PowerStation Plus Mini, it has an integrated Lightning connector.  If you buy one of the Apple-exclusive versions, the battery conveniently charges with any Lightning cable (rather than Micro-USB). The version on Amazon charges via an included Micro-USB cable. It's an expensive battery pack -- and slightly thick -- but it is well designed and reliable. With the USB-out port, you can charge two devices simultaneously.

I've used the $50 PhoneSuit Journey (3,500-mAh battery) for a while and it's held up well over time. With its foldable prongs, you can plug it right into a wall outlet, and it also has integrated Lightning and Micro-USB cables. I've charged another power bank with the Micro-USB cable while simultaneously charging an iPhone with the Lightning cable.

Like the PhoneSuit Journey, the $50 Ventev Powercell 6010+ has integrated folding prongs and both an integrated Lightning cable and Micro-USB cable. But the Ventev is thicker and larger because it houses a larger 6,000-mAh battery. There's also a USB-out so you can charge other devices with an extra cable.

All of MyCharge's Home & Go chargers have an integrated foldable wall plug and USB-out port (or dual ports). However, this version also has a built-in Lightning cable, which is why it costs more. The 4,000-mAh version costs $50, while the 8,000-mAh version runs $70.

The Anker PowerCore Slim 5000 ($30) houses a 5,000-mAh battery and, as its name implies, is quite slim. While it's been around for a few years, it will work with all the latest iPhones (and Android models), but you have to bring your own cable to the charging party.

MyCharge GoExtra is a simple (pictured in the center), slim battery with an integrated fabric loop. The 4,400-mAh version costs $25 while the step-up Go Big (6,000-mAh) costs $5 more and has two USB-out ports instead of one. Additionally, there's a 2,600-mAh Go Mini for $20, and the smallest of the bunch, the Go Style, which you can stick on a keychain (although it's a little big for that), can be had for $10.

The Mophie Powerstation Mini is a very slim -- and slick-looking -- charging brick that houses a 3,000-mAh battery. No cable is included, but you can get these in a two-pack on Amazon for $30. (Only the blue version is available at that price, but it does come in other color options.) 

The Anker PowerCore Lite 10,000 mAh retails for about $35. While it's thicker than some of the chargers in this roundup, it is one of slimmest 10,000-mAh portable chargers and has a USB-C input for charging the battery, but no USB-C output. No cables are included. 

This Anker model is basically an oversized wall charger with a built-in 5,000-mAh battery. It's got two standard USB ports for juicing up your phone and a secondary gadget (or two phones) simultaneously, and a little LED indicator on the side lets you check the charge level at the press of a button. It's available in white, black or lipstick red for $26 to $30. 

The MyCharge Home & Go Portable Charger has built-in foldable prongs so you can plug it right into a wall outlet for charging. The smaller and slimmer 4,000-mAh version costs around $30 and has a single USB-out (no Lighting cable included), while the 8,000-mAh version costs $40 and has dual USB-out ports for charging two devices simultaneously.   

Available in a variety of capacities, MyCharge's Adventure series battery packs are designed to withstand drops and offer both dust and water resistance. They also include a carabiner so you can clip the battery onto a backpack.

Priced at around $23, the Adventure Mini pictured here houses a 3,350-mAh battery that will fully charge most phones. It has one USB-out port (no cable is included) while the step-up Adventure Plus ($25) features a 4,400-mAh battery and dual USB-out ports to charge two phones at the same time.

MyCharge's Unplugged series comes in 3K (3,000-mAh), 5K (5,000-mAh), 8K (8,000-mAh) and 10K (10,000-mAh) models, all of which are portable battery packs with wireless charging capabilities. Additionally, they have a USB-out port or ports for wired charging with a cable (you can charge two devices simultaneously). It's like having a wireless charging pad without the cord. 

They start at $30 for the 3K version, which is obviously the slimmest of the bunch. While the 5K is a little thicker, it doesn't cost much more and probably delivers more performance for your money.    

Moshi's Porto Q 5K (5,000-mAh) isn't cheap at around $85, but like the MyCharge Unplugged, it's a portable battery that doubles as a wireless charging pad. It's swankier and more stylish than the MyCharge Unplugged and charges via USB-C instead of Micro-USB. There's a USB-out port for wired charging, and you can charge two devices simultaneously. 

The Belkin Boost Charge comes in 5,000- ($40) and 10,000-mAh ($50) versions. The higher capacity model (pictured above, left) is one of the slimmer 10K power banks currently available, weighing 7.48 ounces (212 grams). While neither comes with a Lightning cable, one of the Boost Charge's key differentiating points is that you can charge with a Lightning cable so you don't have to carry around a Micro-USB or USB-C cable to charge it.

The 5K version (pictured above, right) has one USB port; the 10K has two USB out ports for charging two devices at the same time.

If you're looking for a portable battery that can also play music, the Esquire Mini 2 ($130) is a slick Bluetooth travel speaker that has a USB-out port for charging devices (no Lightning cable included). It sounds surprisingly good for its slim size.  

We used all of the models above in anecdotal testing during recent weeks and months. The ones highlighted above are ones we recommend over the dozens if not hundreds of others currently on sale at Amazon and elsewhere, which is why we zeroed in on a handful of favorite brands: Mophie, MyCharge and Anker, with some notable one-offs from PhoneSuit, Moshi and Harman Kardon thrown in for good measure.

Here's a few things to keep in mind when shopping for battery packs:

Originally published March 2.Update, April 29: Adds MyCharge Adventure Mini and Belkin Boost Charge.

Best laptops for college students: We've got an affordable laptop for every student.

Best live TV streaming services: Ditch your cable company but keep the live channels and DVR.

Best home security systems: Yes, shopping for the best home security system can be a confusing headache. Fortunately, we've done a lot of the legwork for you.

Best AirPods accessories: Here are some of our top picks to enhance your AirPods experience.