I’m going to show you how to reuse these batteries, diverting valuable and hazardous substances from landfill while acquiring free batteries for your microcontroller projects.
The Shift to Single-Use Vape Devices
It’s ridiculous… How do vape companies get away with putting perfectly good rechargeable lithium batteries in a single-use device? And why does it seem like there are so many more of these around all of a sudden?
I think the shift has something to do with the Juul ban. Juul had a significant share of the market with its rechargeable, cartridge refillable device. When it was pulled from the US market in 2022 by the FDA, new competitors popped up to fill the demand, in a market where now brand recognition could mean a target on your back from regulators. So they’re not incentivized to make a refillable system. And selling you a completely new device every time the old one wears out is more profitable than selling you just a cartridge. Unless lithium becomes much more scarce, or it becomes a legal requirement to make them infinitely refillable, I don’t see this trend changing anytime soon, unfortunately.
I did find some brands that do have a charging circuit included, to make use of a larger liquid reservoir. But once the liquid runs out, the device is still intended to be thrown out.
How did I get this many devices to take apart? Besides picking them up off the sidewalk, I asked my local Buy Nothing group and found a few willing folks who knew better than to throw these in the trash and were happy to offload their hoard.
Lithium Battery Overview
Lithium batteries are used in many everyday devices like laptops, cell phones, hybrids and electric cars. They are much lighter than traditional alkaline batteries and can last much longer. They can also be recharged multiple times. So it’s no wonder that they’re in everything nowadays.
Lithium batteries contain layers of materials folded up together into a small shape. Energy is stored on either side of a battery “stack” and it wants to get from one side to the other, and we power our circuits by making the charges do work for us along the way. As the battery discharges and produces an electric current, lithium ions are released by the anode to the cathode, causing a flow of electrons from one end to the other. When charging, the opposite happens: the cathode releases lithium ions, which are then obtained by the anode. You can think of the act of charging like pushing the energy back to the other side so that it can be ready to go again. And if the layers are breached by, say, a puncture or by crushing, the battery can become shorted out, and the electrons get way too excited.
The C rate is the measure of how quickly the battery can be discharged and recharged without damaging it. Failure modes include overcharging, over-discharging, and short-circuiting. Always use a charging rate appropriate for the battery’s C rating, or a conservative guess.
Here’s a list of do’s and don’ts when using LiPo batteries:
- Charge your battery slowly and evenly, at a rate appropriate for its capacity.
- Store your battery in a cool place
- Get a fireproof battery bag to keep your batteries in
- Don’t charge or discharge your battery too quickly or let it get too hot
- Don’t leave your battery unattended while charging
- Don’t discharge your battery below its minimum voltage level
Taking Apart the Devices
Taking apart anything with a lithium battery in it is dangerous. You have to be careful not to damage the battery or short it out, or you could quickly have a concentrated fire hazard on your hands. So, don’t do this at home without the supervision of someone who knows what they are doing!
I cracked open the cases using an awl and hammer to apply force to the seams in the plastic enclosures.
Then, the whole circuit and tank assembly usually slides right out. If it doesn’t, you can reach in with pliers and pull on the plastic tank– not the battery or its wires.
I recommend wearing gloves when handling and disposing of the liquid tank, and give the battery a wipe before removing them. When I didn’t, I had a hard time getting the stink out of my fingers even after washing my hands. This whole process is pretty smelly, and I think you can absorb the ingredients through your skin too.
Here are some examples of the batteries I found inside. These 280 and 350 mAh batteries are about five dollars retail, and perfect for wearables or other portable projects.
I desoldered them from the other circuitry, and soldered the two wire connections to a new JST plug, with plenty of heat shrink tubing to insulate the connections and relieve any strain on the tiny battery wires.
Charging the Batteries
To charge these up, you can’t just connect them to power. You’ll need a charger circuit with appropriate settings for the size of the battery. The charger monitors the battery and fills it up gradually and safely.
Some have a dip switch so you can toggle the charging rate, like the one shown on the left. You should choose the fastest rate without going over the capacity of the battery. So, for example, for a 350mAh battery, I’d choose to charge at 300 mA. Others have solder pads you can bridge to set the charging rate, like that shown on the right– I chose 200 for the 280 mAh batteries.
You can find the components I used linked below:
The large-capacity devices are nice for reusing because they come with a charging circuit. It’s been interesting to see that which charging chip varies quite a bit. Some are integrated overvoltage and overcurrent protection chips, but others just put a couple of PNP transistors on there and call it a day. So depending on the quality of the included charge circuit, you may wish to use it… or lose it.
I included the information that I could track down about the charging components I found below.
|Over Voltage and Over Current Protection IC|
|current limiting/overvoltage protection IC chip|
PNP Small Signal Transistor
Protection Circuitry & Safety
The difference between these batteries and the nicer ones you might buy is the protection circuitry, or lack thereof. Lithium batteries can be damaged if they are drained or charged too much or too fast. Good hobby batteries will have a little circuit on them that cuts off the power when their voltage dips too low, and protects against shorts and dangerously high current with an overcurrent cutout, These batteries usually don’t have any of that, so you need to add that circuitry yourself or leave the battery connected to a charger that has protection circuitry built-in, and is set to the proper charging rate for your battery.
To protect against accidental shorts after the battery’s out of the enclosure, I added some tape and heatshrink to the exposed contacts. Obviously it’s not a great idea to be adding any amount of heat to these batteries, so I was very judicious.
This electrical tape isn’t the best kind, either. You should use high-temp Kapton tape, but this is better than just chucking all these bare batteries in a box together.
When the device designers put these together, they knew the current draw would never exceed that of the air sensor and heater. When reusing these batteries, thermal runaway could be a real concern– if your circuit draws more current than it is rated for (the conservative rule of thumb is the battery capacity per hour), you could start an unstoppable chain reaction inside the battery that causes it to explode. Remember the Samsung Galaxy Note 7?
So in conclusion, I encourage you to pick these devices up if you see them littered, and at least get them to proper e-waste recycling, and maybe use them to power your next solar device.
Here are a few projects that I think would be a good fit for these batteries:
- Glowing Eyes Costume
- Unicorn Horn with 3D Printing & NeoPixel LEDs
- IoT Muscle Sensing ‘Sup Brows with Kate Hartman
- Remember the Whee-Lo?
- Knife Sharpening Angle Coach
- Internet Valentine w/ ESP8266
- NeoPixel Tiara for Birthday or Prom
- Heart Rate Badge
- NeoPixel Punk Collar
Thanks so much for being here and here’s wishing you safe battery harvesting.