Power Arduino with a 3.7v coin battery

I think I know the answer. But, I just know that I don't know anything, so ask for a 2nd opinion, because it seems to be too good to be true.

I just found these 3.7V 550mAh batteries:

1- With a voltage regulator from 3 to 5V, connecting it with this Arduino: https://www.amazon.com/-/es/gp/product/B08CN5YSQF/

It's going to work, right? (I am making a wearable and if I use the typical yellow 3.7v lipo battery it would be great).

2- Do you know a smaller Arduino? Just out of curiosity, since the size of that one I just showed serves me well.

3- To charge it I am thinking of using this module: https://www.amazon.com/-/es/hiletgo-Batería-18650-Junta-módulo-proteger/dp/B00LTQU2RK/

... and this one to regulate the voltage: https://www.amazon.com/-/es/Comidox-power-elevation-voltage-converter/dp/B07L76KLRY/

My sensor has a consumption of <160 mAh
Arduino SAMD21 has a consumption of <3mAh

Maybe I use two batteries to get 1100mAh.

What do you think? Do you see any errors?

Those batteries are not rechargeable.

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It says those are 3V cells, not 3.7V cells.
Also, NOT rechargeable!

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What sort of life do you think you will get out of a battery like this? Typically less than an hour in my experience.

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As Grumpy_Mike said, the bad news is that while those batteries have a 550mAh rating, you won't get much life out of them the way you want to use them. They are rated at a maximum discharge of 10mA, so you would probably get 55 hours life at that point, but the intended use case is for very low current operation: typically 1mA or less.

This battery and this charger would also be a good solution.

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I'm already seeing my mistake. Although, if you know of a similar battery (I like them because they are very thin and small), I will appreciate it if you share it.

However, I am looking at one that can help me: https://www.amazon.com/-/es/Recargable-serial-number-0-079-connector/dp/B097BL6FRP/

600mAh 3.7V
3.5cm x 3cm x 0.6cm that would work for loading and unloading, right?

What you really need to do is go beyond what Arduino environment offers for you by default and dive into microcontrollers power saving modes. Takes bit of learning and experimenting and good meter to measure low currents, but its doable. After that you can start worrying about what sort of battery you need.

If that arduino gadget keeps running all the time, that tiny battery will perform very poorly and you are lucky if it lasts a half a day.

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But, the microcontroller I showed does not consume much power (Less than 3 mAh as I read), and it is small:

Or am I wrong?

is a measure of battery capacity.

Very rough estimate of battery lifetime in hours = (battery capacity in mAh)/(average current draw in mA)

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How much less?

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You continually seem to think that the current consumption of a device is expressed in mAH. This is only used to give battery rating not current ratings. For current ratings it is simply mA.
It might not seem a big deal to you but it is showing us that you are very reluctant to relearn things you have understood incorrectly.

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This starts to approach quickly a training course of low power design basic's.

For starters you need to measure all current your system eats, sensors, controller, etc...

Then you take a look what you can do to minimize power required by these parts. For example sensor that read once every 10 minutes, probably don't need to be powered rest of 9 minutes and 55 seconds.

Also controllers often have operating modes that minimize power usage.

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And battery selection. Along with this, battery care and recharging methods.

Required reading. It may be seem like a slog, but it is worth any time you devote to it:

As noted, a meter with very low current range(s) is essential.


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