Use external battery to reduce recharges?

[EC-Pro]

I plan to mount 3 x Pro model cameras on a rental property in locations that aren't easy to reach.  Recharging the batteries will be inconvenient and require using a latter to unmount the cameras.   I'd like to leave an external USB phone recharger type battery connected to the camera to extend the life of the charge.  

Will this work?

Any concerns? 

Another option is the solar panel.   Is the Arlo panel the only option? 

Thanks

[Streak2]

I have tried using the phone power banks. Unfortunately they do not work in this application.

The solar panel option does work well. I have had one running now for a few years.

[michaelkenward]

Solar cells are one option, but that does not provide the extra features that you get with permanent power.

Arlo Outdoor Power Adapter for Arlo Pro, Pro 2, Go and Arlo Security Light - Black