One of the best entry-level portable batteries I’ve tested is $100 off for October Prime Day

What’s the deal?

My favorite compact portable battery, the EcoFlow River 3, is currently $100 off, available for $159 for Amazon’s Prime Big Deal Days.

Also: The 50+ best early October Prime Day 2024 deals to shop now

ZDNET’s key takeaways

The EcoFlow River 3 is a new compact portable battery available for $259, but currently discounted thanks to October Prime Day.
It’s portable and lightweight, making it easy to carry. It features fast charging, going from 0% to 100% in 55 minutes, and has a 245Wh output capacity.
Since portability is a priority for the River series of portable batteries, they’re much less powerful than alternatives and best suited for smaller tasks or shorter use times.

EcoFlow has announced the addition of three new portable batteries to its lineup: the River 3, River 3 Plus, and Delta 3 Plus. While the new batteries are now available for purchase, I’ve been testing the EcoFlow River 3 for the past couple of weeks to see how it performs, and I couldn’t be happier with it.

Also: EcoFlow portable power stations are over 50% off with these early Prime Day deals

The EcoFlow River series is a group of portable batteries that prioritize portability and convenience, making for lightweight units that can go almost anywhere. The Delta lineup prioritizes power, meaning that while they’re still technically portable, EcoFlow Delta batteries are heavier and bulkier than River units, as evidenced by my garage’s almost 200-lb Delta Pro Ultra battery.  

I’ve tested Delta and River portable batteries and thoroughly enjoyed testing the latest River 3, which has become my favorite portable battery. The River 3 doesn’t compare directly to the Delta series; they’re built for different purposes. Still, the River 3 is compact and lightweight enough to carry around to charge small devices or to place next to a device somewhere far from a power source.

The River 3 is a small, entry-level battery that weighs under 8 lbs. It is perfect for carrying everywhere you may need extra power with little compromise. For Pete’s sake, this battery is lighter than my third child was at birth. 

EcoFlow has described the River 3 as having a 245Wh capacity. I tested its usable capacity, which manufacturers indicate should be about 85% of its advertised capacity. The usable capacity is the amount of energy that can be used from the battery under normal operating conditions. This often differs from the advertised capacity due to voltage cutoffs, safety margins, and operating conditions, like temperature.

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During my tests, the River 3 had an average usable capacity of 205Wh, about 84% of the advertised 245Wh. The hotter the battery got, the lower this percentage fell, which is to be expected. This number could go up to 87% in optimal conditions, though never higher. This is good enough for my personal use of a portable battery, which is pretty casual, as the worst it’ll see is a camping trip or a short power outage.

The EcoFlow River 3 is powerful enough to offer a 300W output and up to 600W with X-Boost technology, but quiet enough to use in my office without distractions. It can run without a fan when the output is under 50W, making it completely silent compared to larger batteries.

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The battery’s ports include two AC outputs, two USB-A ports, one USB-C port, and one DC carport. EcoFlow says the EcoFlow River 3 has a 20ms switchover, a two-year warranty, and an IP54 rating, which means it can withstand light rain and water splashes.

I tested the fast-charging capability by draining the battery completely to 0%, then plugging it in and monitoring how long it took to reach certain points. The EcoFlow River 3 took 18 minutes from complete depletion to 50%, 36 minutes from 0% to 75%, and 55 minutes for a full 0% to 100% charge. 

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Other mediums take longer to charge the River 3. You can charge it in your car during a road trip and have it fully charged in under three hours, ready to keep your small devices charged for the length of a camping trip. It has a solar input of 110W, so it can charge up to 100% in about three hours with solar panels and direct sunlight, though your mileage may vary.

ZDNET’s buying advice

The EcoFlow River 3 is a great entry-level portable battery if you’re looking for a compact power source to charge smartphones, tablets, and laptops or keep the lights on during camping trips. It’s also a good choice if you’re looking for a dedicated backup battery for certain devices, like powering some lights, a TV, or a CPAP machine during a short power outage. 

Many portable batteries may perform better for certain circumstances than the River 3. Compared to River 2, the EcoFlow River 3 is smaller and easier to carry, using GaN to make it more efficient and compact. My husband, for example, has become extremely attached to the Anker Solix C300 DC, a competitor of the EcoFlow River 3 with a 288Wh capacity.