I have a device (the wii "sensor" bar, basically an IR LED array) that the literature says takes 7v. I can't find any battery offerings that come in 7v, but many that are 3.7v, so I am stuck trying to find some other solution.
Optimally, I want to create a rechargeable battery pack that is cheap and can give me those 7v, while also being small and practical (no 4x AAA for example).
I am considering three different options.
I have a 12v A23 cell, so perhaps a rechargeable A23 cell stepped down to 7v. But I have little knowledge and no experience with step down converters.
Another option is to connect two 3.7v batteries in series, but I read in a comment that this would require a balancer, because otherwise one of the cells might, uh, burst when charging. I had not heard about a balancer before, but I have an old laptop battery with 18650 cells that I had taken apart and it seems to contain a component that looks like that's what its purpose was.
The last option is to use a 5v source (like a small power bank) with a step up converter. But again, little knowledge and no experience on the matter.
So how should I go about it? I have lipo charger boards (I think they are TP4056) that I got some years ago and could probably use for this, and a cheap dollar store powerbank that uses an 18650 cell with usb connectors (but it gets really hot).
Any help or direction would be greatly appreciated.