Quick project. I found one of those small Bluetooth receivers where you can just plug your existing speakers with a jack connector, on the listings I found for it it claimed, the same device, a battery life from 6 to 8 hours. In reality it barely breaks 4h of continuous use, which makes it useless for the purpose I had in mind, so let’s make it better.

The receiver
The device as shown on any e-commerce site.

At the same time, I had a bunch of 18650 lithium cells to spare so I decided to perform a small battery life upgrade on the device.

A puny lithium cell, and its replacement
Just a small upgrade.

After checking the voltages match, and nothing else really, I desoldered the original cell, and soldered in the new one and checked if it would work and charge.

Testing the upgrade
Truth be told, I was afraid something would catch on fire.

After checking everything works, the final touch was making it more convenient to carry, so with some zip ties, hot glue and duct tape (engineers’ essentials) The result is not too bad looking, although it may raise some eyebrows at an airport security checkpoint.

Beautiful result
I swear is just a Bluetooth receiver, agent.

Regarding the battery life, it went from 4 hours to 48 hours of continuous use and counting, a whole magnitude better.

In convenient chart form