You can interact with the ISAPI interface using a cURL tool on a command line terminal window. I use Linux so tools like curl are fairly standard, if you are on Windows I don't know if it includes curl or if you can download a curl tool but assuming you get a curl tool...
So cURL is basically just a command line interface to GET (receive) data or PUT (send) http/https data.
I use ISAPI in a script to reboot some cameras which regularly crash for some reason so taking that as a simple example I send a PUT request to a camera (I am not actually sending any data in this example, as the reboot command does not need any data):
Code:
curl -X PUT "http://admin:PASSWORD@CAMERA_IP/ISAPI/System/reboot"
Obviously replacing PASSWORD and CAMERA_IP with the relevant details. This is of course sending an admin password in clear text over the network. You certainly would NOT want to do that over the internet, but for a private network and to keep thing simple for this example let's go with it...
All going well the camera reboots.
So for your overlay I suggest you send a GET request to the camera to confirm you can get it to work and see exactly what XML you get back:
Code:
curl -X GET "http://admin:PASSWORD@CAMERA_IP/ISAPI/System/Video/inputs/channels/ID/overlays/BatteryPowerOverlay"
According to the spec it should return the BatteryPowerOverlay XML, which (I am guessing here) will show disabled.
Then to set to enabled you would probably need to send a PUT request with adjusted BatteryPowerOverlay XML data where the XML is set to enabled. Something like:
Code:
curl -X PUT "http://admin:PASSWORD@CAMERA_IP/ISAPI/System/Video/inputs/channels/ID/overlays/BatteryPowerOverlay" -d "YOUR XML HERE"