Ode to the AA Battery

Recently this post from @Merocle caught my eye:

I'm fixing my iFixit soldering station. I haven't used it for a long time and the battery has gone overdischarge. I hope it will come back to life. Unfortunately, there are no replacements available for sale at the moment.

Devices with built-in rechargeable batteries have been bugging me a lot lately. It's convenient to have a device you can take with you and use anywhere. And with modern Li-ion cells, battery life is remarkable.

But for years, I've noticed the same thing happening to many devices as Merocle mentions above:

I purchase the device, charge it to 100%, use it a bit. Knowing Li-ion cells are better off in the 40-80% range, I store the device with the battery at that charge level. The next time I go to use the device (a few months later), it won't power on. I plug the device in to charge, and 1 in 4 times the device won't start charging!

One problem is many devices don't have a proper BMS integrated into the charging circuit, that will cut power before the battery is below a critical threshold. Li-ion cells start to have problems below 3V, and often suffer permanent damage below 2.5V.

Devices from even the most stalwart right-to-repair companies suffer from undervoltage issues.

You can sometimes revive 'dead' Li-ion batteries, but I don't recommend it unless you know what you're doing.

Assuming most people don't know what they're doing, when they pull out a piece of gear that won't turn on and has no obvious way of being repaired (especially with odd pouch-cell batteries, much less 18650 cells), these devices will most often end up in the trash. Or if you're lucky, some people will try recycling them.

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