Ode to the AA Battery

Summary

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.Enter the AABecause of this trend, if I need portability, I look for devices that use AA and AAA batteries.Each year for the past 14 years, I buy sets of Panasonic eneloop batteries to replace disposable AA batteries as they die. Eneloops have around 2000 mAh of capacity (versus 2100+ mAh for good alkaline batteries), and ...