General > General Technical Chat
Lithium AA and AAA cells - interesting behaviour.
Zero999:
There's no need for anything fancy. It's easy to build a buck converter which simply outputs 36.6% of the input voltage, which will give about 1.5V, with 4.1V in, down to around 1.1V, when the input has fallen to 3V, by which point the battery under voltage protection kicks in and it cuts out.
thm_w:
--- Quote from: Zero999 on March 15, 2024, 10:31:44 pm ---There's no need for anything fancy. It's easy to build a buck converter which simply outputs 36.6% of the input voltage, which will give about 1.5V, with 4.1V in, down to around 1.1V, when the input has fallen to 3V, by which point the battery under voltage protection kicks in and it cuts out.
--- End quote ---
I'm not aware of any that work that way though, they regulate the output to 1.5V:
http://lichiwei.com/product.php?id=13
tom66:
I would imagine that these devices are high volume enough now that you could build them to have a custom PMIC inside them.
Such a device could precisely measure the charge in and out of the cell and adjust the terminal OCV so that it matched a real alkaline, against something simple like an 8 point look up table.
But maybe I'm dreaming.
Halcyon:
A word of warning with Lithium primary cells and wireless mice (could apply to other consumer products as well).
I have had issues in the past where a fresh set of Lithium cells measured a voltage higher than what you would expect from regular AA batteries. It was so high that the mouse refused to even power on until the cell voltage decreased slightly. To get around this, I partially discharged the batteries.
IanB:
--- Quote from: Halcyon on March 16, 2024, 02:44:12 am ---A word of warning with Lithium primary cells and wireless mice (could apply to other consumer products as well).
I have had issues in the past where a fresh set of Lithium cells measured a voltage higher than what you would expect from regular AA batteries. It was so high that the mouse refused to even power on until the cell voltage decreased slightly. To get around this, I partially discharged the batteries.
--- End quote ---
Not the kind of battery in this thread, but yes, I think Energizer Lithium cells start out around 1.8 V, which is too high for some devices. Same with nickel-zinc rechargeable cells, which also top out at a pretty high voltage.
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