firehazard

Lithium deserves to live

Welcome to the material that will be mentioned in my future eviction notice.

My goal is to use blunt force against the nicotine-soaked casings of all kinds of disposable vaporizers (or possibly beer-soaked casings of old laptop batteries) and then dig out any precious lithium that might be hiding in the ruins.

Things to find out

I want to see how long can these cells actually last. I'm imagining either a small 1-cell pack with a small solar panel that could run indefinitely for at least 300 cycles, or a heftier 1s4p configured pack. The powered device could possibly be an ESP32 microcontroller or similar. Bigger packs could easily power an entire Raspberry Pi for longer periods, but charging would be challenging.

I want to gather some solid stats before I start building around the batteries, I don't even know if they're worth the effort yet.

Fieri Beginnings

I have decided to start with a bunch of elf bars that my friend gave me. You can see them on the photo on top.

Upon pulverizing their bottoms, the Elf Bars have graced me with a variety of putrid smells, which have unfortunately completely penetrated the lithium cells. I do not recommend washing them, that might be dangerous. At least the vomit-inducing vapour serves a useful purpose in the security of this project: When a cell starts overheating, your nose will be notified.

Oh, why talk about overheating in the first place?
Because when I started with the tests, I had no idea what the C rate for charging the cells was, so I just shoved them in my low power USB multi purpose battery charger and waited for some results. It was only after a few charged cells that it occured to me to check the maximum charging current - I realized that I have never worked with such small capacities in lithium cells before, so a charging current of 1 A seemed like no big deal to me.

I have identified one of the possible cell suppliers and their datasheet.

If this information applies to my cells, then the maximum charging C rate is only 1, which means that I can only pump up to 550 mA to each of them - even less to some of the smaller ones. The maximum allowed current can go as low as 360 mA.

Of course, my cheap generic brand USB lithium charger will happily provide them with 2 A, so during the initial testing, the pillows might've gotten a bit spicy. There is no setting on the charger that allows limiting the charging current. Oops.

The charger has four charging ports and a total maximum output of 2 A.

If all four slots are occupied with charging or discharging of a cell, each of them will handle 500 mA max.

So, to keep the charging at least under 500 mA, I need to have all four ports occupied (by charging or discharging). During the testing cycles, it can often happen that half of the slots will finish their cycles and stop counting as active - which then momentarily increases the potential charging current of the other two cell slots and spicyness is revived yet again. Actually no, it's probably not safe at all to attempt to use this charger for testing the vape cells. I'm working on a solution.

Charging cycles

I try to document as much as possible about the lifecycle of harvested lithium cells so that I can understand how they actually perform after many charge / discharge cycles. Datasheets are nice, but the storing conditions of the cells are rarely ideal. We can at least read one bit of crucial info from the cell itself, which is its manufacturing date.

What is a test cycle?

This is a built in test mode of my charger. When it's activated on a cell, it will first charge it fully to 4.2 V, then it will slowly drain the cell at roughly 350 mA until it reaches 2.8 V. After the discharging finishes, the measured capacity is printed in mAh on the display and the charger will then run a normal charging cycle back to 4.2 V.

Data recorded from simple charger built-in test (data is still being collected)

Test cycle data is in mAh

13400 type cells

• Designated capacity: 550 mAh
• Average discharge time from 4.2 V to 2.8 V at 350 mA: 90 minutes
  • Measured by the USB charger

13300 type cells

• Designated capacity: 360 mAh
• Average discharge time from 4.2 V to 2.8 V at 350 mA: 45 minutes
  • Measured by the USB charger

How disposable is disposable?

This is roughly what I'm dealing with

Source: https://www.patlcell.com/en/product/product-414.html

The webpage also says the following:

super power, The continuous discharging current can be 5C-10C without over-heat

.. which implies that the peak output current could actually be somewhere around 5500 mA? Let's find out

Also notice the low charging rate. Makes sense for a battery that gets charged only once during its lifetime, but it complicates things a bit for me. Some of the cells were charging way above 2 C on my USB charger.