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Comment by DavideNL | Hacker News Reader

Somewhat related: my Netatmo weather station sends me an e-mail every few weeks that i should replace the battery of one of the modules. I assume it doesn’t like rechargeable batteries. I never replace them, can’t disable the e-mail.

Support can’t fix this of course.

So I’ve setup a server-side e-mail rule to send all netatmo.com emails to the junk to prevent being constantly spammed by them.

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Is it powered off AAs? Rechargeable batteries have lower voltage than non-rechargeable ones[0], so maybe the module is a bit oversensitive when trying to guess the battery is about to die.

[0] - With batteries I have around the house, it's 1.5V nominal voltage for typical non-rechargeable AA, vs. 1.2V for rechargeables.

However the voltage on alkaline batteries drops pretty linearly from 1.5v to 1.0v, while rechargeables maintain close to 1.2V for most of their discharge, then drops off quickly:

https://www.boat-project.com/tutorials/aa_batteries.htm

That's why rechargeables work in most devices, since alkalines are 1.2v or below for a good chunk of their useful life anyway, most devices are designed to work fine with 1.2v.

If a device actually needs 1.3+V to function properly, alkalines won't last long, you'll want to use 1.5V lithium batteries.

Aren't all the lithium batteries of the sort you're talking about labelled as 3v? A lithium cell would need a buck circuit to do 1.5v

I'm talking about AA, which are always 1.2-1.5V as far as I know. Like these:

https://www.amazon.com/Energizer®-Ultimate®-Cylindrical-Lith...

> A lithium cell would need a buck circuit to do 1.5v

Maybe? I have no idea how they are built.

yes, those have a buck converter built in to drop the voltage from 4.2v (fully charged) to 1.5V - and ideally they should be able to provide 1.5v from full to flat.

In a similar vein, those USB power banks use 18650 batteries (generally, some use LiPo or LiFePo packs instead) - but USB needs 5v (and ideally 5.xx where xx is determined by the cable resistance so the actual output at the terminating end is 5vdc, so the power bank may actually put 5.33V into the USB A side and get 5vdc out the load side, due to current draw.) so instead of a buck converter, a single cell or parallel cell bank will use a boost converter, to bump 3.6-4.2vdc to 5.x volts.

You may have known this but someone else might not have. A common circuit for boost conversion is called a Joule Thief.

Yea you’re probably right… it’s these batteries:

https://www.amazon.com/Panasonic-BK-4MCCA8BA-eneloop-Pre-Cha...

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