[tzs]

I've been a bit puzzled by the 1.5 V lithium AA batteries I see on Amazon. They say they are a constant 1.5 V all the way from 100% charged to 0% charged.

With the battery presenting a constant voltage, wouldn't that make battery level displays useless? They rely on the voltage declining as the battery discharges. With a constant 1.5 V battery your device is going to say the battery is full right up until it suddenly stops.

I'd expect that to get very annoying.

Edit: I mean the 1.5 V lithium rechargeable AA batteries, like these: https://www.amazon.com/Deleepow-Rechargeable-Lithium-Batteri...

[grumbel]

The AA lithium-ion rechargeable are internally 3.7V, just like any other lithium-ion battery. They have a buck converter build-in that regulates that down to a constant 1.5V. Which can be handy in the handful of applications that don't deal with the 1.2V that NiMH provide. This does in turn make battery indicators indeed completely useless for many of them, as there is no detectable drop in voltage from the outside of the battery.

However, there are newer ones take care of that and regulate the voltage down to 1.1V or so shortly before they run completely out of juice, so that the battery indicator can give a warning. Don't know how widespread that feature is yet, but it exists.

[dragontamer]

When in doubt, https://data.energizer.com/

For Lithium chemistry: https://data.energizer.com/pdfs/l91.pdf

That's Energizer's Lithium of course, but you can expect that competitors probably perform "similarly".

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You can see that Energizer Lithium is 1.7V, slightly more than the 1.5V found in typical Alkaline cells. Today's electronics are pretty flexible however, and this may not be an issue. (In practice, AA-devices are usually designed for 1.35V NiMH, 1.5V Alkaline, and 1.7V... but there are some devices that have made 1.5V assumptions and _ONLY_ work with Alkaline)

[tzs]

Oops. I meant 1.5 V rechargeable lithium AA batteries, but left out "rechargeable". I've edited my comment to fix this.

The 1.5 V rechargeable lithium batteries couple a rechargeable lithium cell with a buck converter to drop the voltage to 1.5 V.

I haven't seen any that are sophisticated enough to use a variable output buck converter and drop the voltage as the underlying battery discharges.