Hello all... I have a partner ACS with partner mail. On Extension 10 and 11 I have a message indicating change sys bat with power on. Any ideas on how to do this? Should this be done by my installer or something I can do myself???

You will find the printed instructions in the installation manual, that your installer should have left behind. If not, you can download it (for free) from https://support.avaya.com

You need 2-AAA batteries, they go into the main module of the phone system, which may or may not include other modules. Thus, it would be best to look at the manual so that you can identify the parts, or rely on a local installer to do it for you.

PM sent to SteveM11