The Galaxy Note 9 already has fantastic battery life, but sometimes things happen. Maybe you're going on a weekend camping trip without power, or maybe you just forgot to charge your phone overnight and have to rush out to work. Whatever the reason, a battery case is always handy to have. It adds significant thickness to the already huge Note 9, but that's better for some than having a dead phone in your pocket.

Lifelong warranty

ZeroLemon Slim Power

The Slim Power case provides the Note 9 with an additional 5000mAh battery pack and features a "chinless" design that keeps the height of the phone to a minimum. Just like the Note 9 itself, it charges over USB-C and even supports passthrough charging. At just $40, it's hard to argue with the Slim Power case, even if you only buy it to have around as a backup and don't use it every day.

$40 at Amazon

Good for a year

Moonmini Battery Case

Moonmini isn't as well-known as ZeroLemon, but its battery case offers the same 5000mAh cell for $10 cheaper. In fact, it looks like a nearly identical model — though you won't get the same lifelong support after your 1-year warranty expires. The ZeroLemon might be a better option for that reason alone, but if you're looking to save every dollar possible, Moonmini seems to offer the exact same case for less.

$30 at Amazon

More of the same

Punkcase 5000mAh Battery Charger

Noticing a trend? A lot of these battery cases feature the exact same design, likely being made by the same manufacturer. Just like the ZeroLemon Slim Power, Punkcase offers a 5000mAh with a lifetime warranty and passthrough charging over USB-C. The power button lets you turn off the case to run off of the Note 9's internal battery, and you can check your charge level with the four LED indicators on the back.

$40 at Amazon

Wireless charging

Mophie Juice Pack

Mophie is the most recognizable brand on this list, but while its case is one of the better-looking with a slim design up top and a nice pattern on the back, it's a hard sell at $100 with only a 2525mAh battery. Still, the Juice Pack supports wireless charging just like the Note 9 itself for easy top-ups. and the speaker grills on the bottom reroute your audio to come from the front of the phone.

$100 at Amazon

Modular case

i-BLADES Smartcase

The i-BLADES Smartcase is a thin polycarbonate case that uses magnets to attach a separate 1800mAh battery pack. In addition, it houses additional storage for your phone, along with an extra microSD slot. With a much smaller 1800mAh battery compared to the alternatives' 5000mAh cells, it's hard to recommend the i-BLADES case for a whopping $99, but it's a unique and extremely slim option that provides just a bit of extra juice.

$99 at i-BLADES

If you need to extend the battery life on your Galaxy Note 9, the ZeroLemon Slim Power is probably your best bet. If you don't mind questionable aftermarket support, however, Moonmini's case is identical for a few bucks cheaper, and the i-BLADES Smartcase is an interesting option in its own right. Mophie's Juice Pack is the best-looking of the bunch and supports wireless charging, but its high price and low battery capacity make it a hard sell.

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