Recharging 9 Volt Li-Ion Battery

[JamboTheRuminant]

Hello,

I'm working on an electronics project using arduino 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?

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.

[MarkT]

If its one of these PP3 sized "9V" LiIon batteries its a 2S pack probably with rudimentary charge/discharge protection, but this might depend on the exact battery you use.  If always powered you only need the load current plus a trickle charge amount.  It might make sense to find a full BMS with charge management for 2S pack.

If its salt water I would worry about the wireless charging power getting dissipated in the water unless the charger and unit are mounted in flat contact.

[5U4GB]

That was my reaction too, you're starting with something that's bunch of kludges and compromises to make it quack like a 6F22 battery, you'd be better off using a BMS with 18650s or NiMH AAs or similar.  Google "arduino rechargeable battery" or similar for lots of discussions on this.

[MathWizard]

Why can't some wires be ran into the waterproof box instead of a battery ?