You Get What You Pay For (Cheap USB Battery Pack is Cheap)

A few days after Christmas I was chatting with my buddy Sean about the winter storm that was about to sweep the nation. Sean lives just outside of Buffalo, New York and was expecting more than two feet of snow. While charging up all our USB battery packs in case either of us experienced a power outage, the topic of charging devices via solar came up. One thing led to another and within the hour I had found and ordered two of these USB battery packs with built in solar panels from Amazon. These charging packs claim to deliver a whopping 36,800mAh of power and and include everything from the aforementioned integrated solar panel to a built in compass! These battery packs typically retail for around $60, but right after Christmas I caught them on sale for $18 and so I ordered two of them, one for myself and one for Sean.

You’ll probably want to read the entire post before ordering one — or, hopefully, not ordering one.

The power pack arrived just a few days later and when I opened the box I was a bit underwhelmed. I own a couple of power packs rated for 20,000mAh and both of them are larger and weigh more than this one. I wrote the difference off to advances in battery technology. The unit came with a full charge and I used it to charge up my iPhone 11 Pro Max, which has a battery capacity of roughly 4,000mAh. Based on the numbers, my new 36,800mAh battery should be able to charge my phone nine time before needed to be recharged itself.

What I didn’t initally notice was that charging my phone nearly completely zapped my new charger. Unlike more advanced chargers with LCD screens and numbers that show the exact percentage of battery life remaining, this charger uses the old LED system: 4 lights for full, three lights for 75% full, and so on. After charging my phone once, the power pack was down to a single LED.

I wanted a more accurate way to measure just how many milliamps this device was truly putting out, and so I went to Google. Thirty minutes later, I had ordered two things: a “USB Digital Tester” and a “USB Dummy Load,” for a grand total of $30ish. USB Digital Testers are small USB devices that can give you information about the amps, watts, volts, and milliamps of the USB port it’s connected to. The USB Dummy Load is a small device that infinitely draws 5 volts and an adjustable amount of amps from a USB port. Combine the two, and you can measure how many milliamps pass through the digital tester before a power pack goes from 100% to 0%, thus giving us an exact number.

For a baseline, I decided to test my 20,000mAh battery. After ensuring the pack was fully charged I connected the USB Digital Tester and the dummy load to one of its USB ports and let it drain. Once the power pack was completely dead I removed the USB digital tester and connected it to another USB port to get the final number of mAh, which was about 11,500 — way less than the advertised 20,000mAh capacity!

A bit more Googling explained the discrepancy. Apparently, all power packs advertise the amount of milliamps their batteries can store… but these batteries are rated at 3.7 volts. USB ports are 5 volts. Inside the power pack, a small bit of circuitry converts the voltage from 3.7v (in the battery) to the 5v needed to charge a USB device. While most of us assume a 20,000mAh would charge an iPhone with a 4,000mAh battery five times, that’s not the case. 20,000mAh at 3.7v is 14,800mAh at 5v (20,000 * 3.7 / 5). And unfortunately, that’s not even a real world number, because some energy is lost in the conversion (lost energy = heat) and so the quick and dirty way to estimate the total amount of milliamps you’ll get out of a charger is to multiple the advertised rating by about 0.6. For my 20,000mAh battery, that would be 12,000mAh, and since the actual number I got was 11,500, that tells me my numbers and math line up.

Next, it was time to test my new 36,800 USB power pack. Multiplying that number by 0.6 gave me 23,160mAh, which is what I was expecting to see.

With a dummy load of 5 volts and 1 amp, the battery provided 5,392mAh of power — approximately 1/7th the amount listed on the package, and less than a fourth of what I was expecting to see. Just to make sure I hadn’t flubbed something up, I did a second test, this time with a 5v/2a load. On that test the battery barely put out 5,000mAh.

To quote Jay Sherman from The Critic… “it stinks!”

To be fair, unless I were to purchase a second unit (which I’m not willing to do) I can’t be entirely sure if all of these are junk or if I just happened to receive a lemon, although I have my suspicions. While not entirely scientific, the fact that this charging unit is physically smaller and lighter than my other batteries, all of which have lower milliamp ratings. Also, the fact that Amazon is selling these at a 70% discount is a red flag. To me this doesn’t feel like a big battery that’s performing poorly. It feels like a cheap piece of junk.

If Amazon didn’t have such an easy return policy, this battery pack would be going right into the garbage. Fortunately, with just a couple of clicks I can get a full refund on this item.

PS: A couple of days ago I ordered this 38,800mAh USB portable charger from Amazon for $31. I’ve spent the past couple of days running it through its paces and can confirm it works as advertised. Sometimes you really do get what you pay for.