When you buy a portable power station, you'll likely see the battery size and power output—but there's an important drawback that often goes unmentioned. Fortunately, while this is a problem, it's one that a software update can fix.

My Anker Solix F3800 Plus has a 3,840kWh battery. Unfortunately, this doesn’t give you the full picture of how long it will last.

If you plug in a fridge that pulls 100W an hour, you could reasonably expect 38 hours of runtime. But that doesn't take into account how the F3800 draws power from its own battery to power itself. Energy is required for the system’s inverter to convert the DC energy in the battery into AC energy that most of our devices and appliances use. This energy usage is referred to as idle drain, since it’s power that will be consumed even if the unit is just sitting there being idle.

Anker doesn’t advertise just how much energy the F3800 Plud drains per hour, but the number has been reported as anywhere from 50 to 70 watts. That means an F3800 Plus left idle without powering itself down would run empty in just over two days without you plugging anything in. This may sound like a lot, but that number shrinks quickly once you start actually pulling power from the unit.

100W from a fridge combined with 70W from the inverter adds up to 170W per hour. At that rate, the F3800 Plus would run out of charge in just over 22 hours. I didn't realize the drain would be this high when I first thought about buying this unit, and while I don't have regrets, it's still a bummer.