I am currently in the middle of a project and I am quite unsure of what type of battery and battery charger I should be using. To be honest I have never worked with battery or battery charger yet.

In this project, I have a 3.3V and 50 uA power source, which is extremely low. Also, this power source is not regulated at 3.3V, so I need some way to stabilize it. Currently, my whole project does work at 30 uA, but I'd like to be able to store some of the power source into some kind of battery. From what I have seen however, this seems to be very difficult as battery requires high current to be charged effectively.

I have currently found an ultra low power energy harvester and battery charger that does seems to satisfy my criteria, but I am very unsure of what battery to use. https://www.st.com/resource/en/datasheet/spv1050.pdf .

Also, about this energy harvester, is it possible to directly take an unregulated power source and plug it directly into the circuit (bypassing the battery) to power on my project?

So if someone with more experience than me could give me his/her input on what type of battery I should use and if it is possible, I'd be very glad to hear it. I am also taker of goods resources to learn on the subject as it is not very well explained in datasheets.

Thanks in advance.

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    \$\begingroup\$ I don't quite understand what you are trying to do.... Are you saying your power source can only supply 50uA? and your circuit only draws 30uA, so you want to use the remaining 20uA to charge a battery? Why?You don't need to use the full 50uA. Can you clarify what your intentions are? \$\endgroup\$ – MCG Mar 5 at 16:14
  • \$\begingroup\$ Oh yes of course. Currently, my power source only supply 50 uA at most. However, I'd like to make a portable device out of my project, so I'd like that my power source could charge up a battery. I understand that it would take a very long time to charge up, but that is fine with me for now. \$\endgroup\$ – Nathaniel Brochu Mar 5 at 16:41
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    \$\begingroup\$ You may be more successful using a Supercap than a battery. \$\endgroup\$ – Jack Creasey Mar 5 at 16:58
  • \$\begingroup\$ @JackCreasey, that is a very good idea I did not explore. Thank you very much! \$\endgroup\$ – Nathaniel Brochu Mar 5 at 17:20
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    \$\begingroup\$ I'm guessing (or I'd make this an answer) that you want to use a small single LiPo cell. I know you can get them down to 100mA-h, and I suspect they're available smaller yet. I believe (but could not swear to this) that as long as your charge current is higher than the cell's self-discharge current it'll charge up just fine, if slowly. You need to think about how long you want the thing to last when it's running on the battery -- that bears directly on what battery you choose. \$\endgroup\$ – TimWescott Mar 5 at 17:37

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