Accessing mesh relay data from the application layer in Zephyr

[AndyM]

Is there a way to access the data that comes into a provisioned node and is relayed on the mesh network, from the application layer in Zephyr?

I have a battery models erver and  I set it up for publishing to a certain address

On another device I subscribed to that address and in the RTT log I  see the data coming in and being relayed by the mesh stack but don't see a way to access it from my application.

There are callbacks in mesh model definitions , i.e BT_MESH_MODEL_CB and BT_MESH_MODEL_VND_CB  that use  bt_mesh_model_cb but it does not have any functions to examine the incoming data. What's the proper way to do this under Zephyr?
Thanks

[AndyM]

Update2

Set up publication and subscription to battery model - all succeeded

Battery client and server set up as above

Tried calling bt_mesh_battery_cli_get(batt_client,NULL,NULL) - get an error -125

Stumped. Please help

Thanks