This DIY Tester Can Help You Identify Fraudulent 18650 Batteries
If you’re tired of sellers overstating the capacity of their lithium batteries, then you’ll want this DIY battery tester.
Consumer marketplaces, including Amazon, eBay, and AliExpress, are absolutely inundated with sellers peddling fraudulent products. That’s especially true for batteries, because most consumers lack the knowledge and tools to test them. If you buy lithium batteries (or products that contain them), there is a very good chance you’re getting scammed and the batteries will have, at the very least, much lower capacities than specified. The result can be anything from an annoyance to a legitimate danger. To prevent that, Open Green Energy designed this DIY 18650 battery tester anyone can build.
The purpose of this device is to give makers the ability to easily test 18650 lithium batteries to verify their capacities. If a seller advertises their batteries as something like 9900mAh, you can use the tester to check that. It will give you a pretty accurate estimate of the actual capacity, such as 3500mAh. In this example scenario, you would return the batteries and avoid that seller in the future. If the capacity matches the specifications, then you’re good to go. But you may be surprised to find how many sellers are mislabeling their batteries.
Open Green Energy previously shared a similar device, the Battery Capacity Tester V2.1. Its job was to safely discharge 18650 batteries (or any other batteries) and measure the total power used. Assuming the battery started at a full charge, that is the battery’s capacity. But that device couldn’t charge the batteries, which was a bit of an inconvenience.
To make things a bit easier, this new version can both discharge and charge 18650 lithium batteries. It can only work with one battery at a time (it would be dangerous otherwise), but it is perfect for testing random samples from newly purchased batches.
The tester is built on a custom PCB that hosts a Seeed Studio XIAO ESP32 development board. It displays the status and measured data on a small OLED screen. Because the ESP32 has onboard Bluetooth and WiFi, it would be possible to create a smartphone app to work with the tester in the future. For now, it has a few modes and the most useful, in our opinion, is the “Analyze” mode. That brings the battery up to a full charge, then completely discharges it (to the safe voltage level) to determine the battery’s capacity. That makes battery testing as simple as possible.
