Back when I was a regular MARC train commuter, I occasionally found myself stuck on a slow-moving or stranded train with an iPhone clinging to 1 percent battery life. In at least one instance, I was forced to borrow a fellow passenger’s phone in order to let my child’s school know I was running late for pickup.

I’ve since learned to carry a portable USB phone charger with me at all times, and they’ve thankfully come down in price and are more reliable than ever before.

There are many different options for those looking for portable power, and it helps to understand the capacity and number of connections you need. Some have more capacity but more bulk, some have sleeker designs while others have more ports. And prices are all over the place. You just need to determine what you need and how much you are willing to spend.

For most people, a pack with a single connection for a cell phone will suffice. Look for something with a capacity of 10,000 milli amp hours (mAh), which will usually allow you two full charges of most phones. It’s worth noting that if you get one of those thumb-size power banks, they usually have barely more than 2,000 mAh and may not be effective.

I am partial to the Xiaomi 10,000 mAh Powerbank, which is very slim and portable and cost about $25. It’s important to note that any charger will work ONLY if you take the time to charge it, too. In other words, don’t assume that your charger is charged! This seems obvious, but I’ve found myself with a dead charger on more than one occasion.

Here are some pages with reviews of other portable chargers out there. We have not personally reviewed most of these items, but hopefully you find one that works well for you.

The Best USB Power Banks and Battery Packs - Wirecutter

The Best Powerbanks of 2018 - TechRadar

The Best Portable Chargers of 2018 - DigitalTrends

The Best Portable Chargers and Powerbanks - PCMag
Best Portable Chargers and Battery Packs - Tom’s Guide