Need a new portable charger? Amazon Prime Day is the perfect time to buy one

People stuck at home don't have to worry much about their phones, tablets, Nintendo Switches or other portable tech running out of charge. But if you're starting to safely venture outside more regularly, Prime Day 2021 is the perfect time to snag a cheap portable charger or power bank and keep your batteries topped off.

Amazon Prime Day always has mystery deals, but there are some tech categories you can safely predict will make an appearance, from budget TVs to Kindles. Power bank deals certainly fall into that 'predictable' category.

Last year, Prime Day 2020 had discounts on Anker, Aukey and RAVPower portable chargers, with savings as high as 36 percent off. This year could see similarly impressive deals.

But it's also important to spot and buy the right power bank. Here's what to look for on June 21–22, and how to decide which deals are worth snatching up.

Looking at Prime Day 2020's deals

During last year's Prime Day deals, we saw a range of portable chargers go on sale, from the lipstick-sized Anker PowerCore+ Mini with just one 3350mAh USB port (20 percent off) to the Anker PowerCore III Elite with both USB-C and USB ports and a 25,600mAh battery ($80 off).

We also saw plenty of other deals on portable chargers both thick and thin, 10,000 and 20,000 mAh, with varying numbers of ports. A 32,000mAh RavPower power bank was $30 off, while a slim 10,000mAh Aukey charger was just $11 total. None of our current top power bank picks appeared, but most of them were well-reviewed by consumers.

Many of the above deals were also Lightning deals. This year, you may see some excellent, limited-time discounts and have to quickly decide if a power bank fits your needs. So let's break down what to look for.

Best portable laptop battery chargers and power banks — (Image credit: Shutterstock)

All about mAh, ports and weight

When choosing a power bank deal during Prime Day 2021, consider which devices you'll regularly need to charge on the go. Most people buy one for charging their phone, which typically has a set battery capacity (or mAh) that you can look up online.

So if you own a Galaxy S21 with a 4,000mAh battery, then a 10,000 or 20,000 mAh portable charger would recharge it 2.5 or 5 times before you had to recharge the charger itself. iPhone 12 owners, meanwhile, have a smaller 2815mAh battery, meaning you'd get 3.5 or 7 recharges.

Phone batteries are getting larger by the year, so even if your phone battery is small, it makes sense to future-proof your power bank and charge one with a larger capacity. But larger batteries can be expensive, making Prime Day a great time to snatch one up.

Similarly, you'll want to check whether your phone supports Power Delivery (PD) or Qualcomm Quick Charge. These allow a charger to refill your phone's battery much more quickly than a normal charger; however, a phone with a limited charging circuit won't be able to handle the extra voltage or amperage, so it'll charge slowly regardless.

Another factor to consider is where you'd put your portable charger. Even a larger one would slot into a backpack or purse, but only a slim charger would fit comfortably in a pocket. In general, a 20,000mAh power bank will weigh upwards of 1lb/0.45kg and measure about 1in/ 2.54cm thick, while a 10,000mAh model will be much lighter and more compact.

A Mophie power bank — (Image credit: Mophie)

You may also want to recharge more than just your phone, or more than one device at once. Most power banks will have at least two USB-A ports, while a few will add a USB-C port, embedded Lightning cables, or even magnetic/ wireless charging options, though these are pretty rare.

If you want a portable charger with a USB-C option, be careful: many power bank listings on Amazon say 'USB-C Input', which means the device itself charges via USB-C but doesn't support USB-C charging.

Typically, just one or two ports will be enough. To charge three devices on the go, you'll also have to carry three charging cables with you, then pull them out along with the power bank and three dead devices all at once. Doing that on the subway would be pretty silly.

If you're more interested in an uber-powerful charger that'll keep all of your devices running, you may want to consider a laptop-charging power bank instead, or even a multi-port charging station that plugs into the wall. We've also seen deals on those during Prime Day.

We can't predict which power banks will go on sale come Monday, or if they'll be any good – but we do know they'll be much cheaper than normal. Hopefully, the above guidelines will help you figure out what to look for, and you can also check our favorite power banks to see our own criteria.