Retailers like Target, Gap, and Under Armour are adding free phone-charging stations to stores.

Target has added free chargers to nearly 200 locations across the United States over the last two years.

Increasingly, customers are shopping both online and in-person — sometimes at the same time — as they rely on mobile phones for checking prices, online orders, and even store maps.

Target, Gap, and more stores are trying a new strategy to convince shoppers to visit stores.

Over the last two years, Target has launched free phone-charging stations in nearly 200 locations across the United States. The lockers, provided through a partnership with ChargeItSpot, have also started popping up at retailers including Gap, Neiman Marcus, Under Armour, and Uniqlo.

ChargeItSpot posits that "low-battery anxiety" is something that afflicts many shoppers — especially as Americans are increasingly shopping online.

According to the company, 64% of shoppers say that they feel panicked when their phone battery is running low. Just 12% were unaffected and 6% were happy, according to a survey of 1,000 people shopping in malls across the US.

Increasingly, customers are shopping both online and in-person — sometimes at the same time. From Thanksgiving Day to Cyber Monday, the most common shopping practice was to mix in-store and online shopping, with the National Retail Federation reporting that there were 89.7 million omnichannel shoppers.

Read more: More people shopped online than in stores this Black Friday

The rise in mobile shopping has been key to this mix. This Black Friday, 33.5% of online purchases were made on smartphones, according to Adobe Analytics data. That marks a significant increase over Black Friday 2017, when mobile accounted for 29.1% of online sales.

As a result, retailers are trying to better meld mobile and in-store shopping. At Target, you can use your phone to signal that you have arrived at stores and are ready to pick up your purchases. Walmart provides store maps on its apps.

Retailers need customers to shop on their phones. So, it makes sense that the companies want to prevent iPhones from running out of juice at all costs.