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I am designing a custom USB hub for a project that will be primarily connected to a Surface Pro or laptop. One of the peripherals that I am using is a camera that consumes quite a bit of power from the Surface Pro/laptop battery. I am thinking that I would like to try to incorporate some extra external battery power separately to this camera to extend the overall time away from a wall outlet--meant to be portable--but I am wondering how to do it.

I am familiar with the way USB and battery charging handoffs seem to work a la the Adafruit Feather, covered here. And I also found a lot of good info here. However, the difference is that USB power will always be present, as the camera is always passing data to software. When the batteries fail, I would like USB to be able to then provide power for the camera. Not sure if it can then recharge the battery too or if I will have to just add a separate charging port for the cells, but that may be a separate issue all together.

I am looking to use Lithium-Ion cells at 3.7V. 18650 cells would be best for the case I had in mind, but I'm open to whatever works. The camera is USB2.0 it appears and requires 5V.

Anybody have suggestions on an IC that can achieve this type of power management? Or is there something I can do tweak some of the desings proposed above to achieve this goal?

Rp Wav
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  • What's wrong with using a pair of diodes from the two supplies? (You'll need to use a DCDC converter to bring the battery to within whatever range your camera uses). As long as the battery gives the higher votlage compared to the USB, it'll supply the current. This will mean you'll have a diode drop of votlage, but that could easily be within operating range of the camera (but you'll have to check that on the datasheet to be sure). – Puffafish Feb 16 '23 at 15:55
  • Assuming the camera draws power via USB you will not be able to change it's behavior much. You might want to take the battery out of it to avoid it wasting power from your other batteries trying to charge itself. There are many powered USB hubs, so it should be fairly easy to inject supplemental power and avoid draining the tablet. – Drew Feb 16 '23 at 16:30
  • USB hubs with external power input already exist. Why not use them? – Justme Feb 16 '23 at 20:13
  • Ideally needs to be completely portable during the day so unable to always use external power. – Rp Wav Feb 16 '23 at 21:59
  • @Puffafish Thanks I'm definitely going to try this. – Rp Wav Feb 17 '23 at 18:35

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