Recharging Arduino Battery

Other Hardware General Electronics
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Hello,

I'm working on an electronics project using an arduino NANO and am planning on have this arduino be permanently enclosed within a waterproof container.
This container will be operating normally underwater. With that being said, I need to charge the battery powering the arduino within this container.

I was looking to use wireless charging but I had a few concerns:

  1. Would a wireless charing circuit need to behave any differently since the battery will always be plugged into the arduino?
  2. What should be the the configuration of the battery between the arduino and charging circuit in order for thermal runway not to occur?
  3. I was thinking about using a 9 volt battery since size is also a consideration for me; Would that affect picking circuit elements?

If someone could please help me find some off the shelf parts or guide me to find a good source of information on this I would greatly appreciate it.

Thanks.

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  1. I don't think so. But the voltage regulator between the battery and the Arduino must be rated for the maximum charging voltage.

  2. Why would thermal runaway occur? Your battery charging circuit would cut off the charging voltage when it detected that the battery is fully charged.

  3. How long do you need the circuit to run between recharges? What type (chemistry) of 9V battery? What capacity would it have?

Generally, 9V batteries are not great for Arduino projects. Most arduino need 5V or 3.3V. If you use a linear regulator like the one on-board the Nano to reduce 9V to 5V, 44% of the battery's capacity will be wasted as heat. If the Arduino is 3.3V, 63% of the battery capacity will be wasted. You can use a "buck" converter, which will only waste 10~20% of the capacity, but if your circuit is in a very low power sleep mode for long periods, the quiescent current of a buck regulator may waste more of the battery capacity than a linear regulator would.

Nano is not a great choice for battery powered circuits. Nano is only available as 5V, there is no 3.3V version.

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  1. The circuit will always be on but it's only really used for 2 hour per day. The battery would just be a Li-ion battery.

circuitarduino
circuitarduino492×583 12.4 KB

Do you think I could wire my battery charger circuit in parallel with the arduino like the picture included? This seems like the simplest implementation since the 9 volt battery will always be plugged into the arduino. I'm worried that this won't work since the arduino will always be on.

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Nevermind I found a TP4056 module that seem to do this exact job. Thanks for your input and help.

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