Electronic Alarms and Home Security Devices - Security System - backup battery

I have a security system with low heat sensors and water bugs (I did not have the alarms for fire and burglery put in). The control box has a back up large 9v battery. The low battery indicator went on. The service guy replaced a wire saying he guessed it shorted. That service call cost $100. And it did nothing. They said for me to buy a new control panel (a couple hundred dollars). I instead bought a new battery and replaced it, and that worked. That was a few years ago. The low battery indicator is again on and I again replaced the battery. The low battery indicator is still on.

Questions: 1) Does the system have to be shut down and restarted or something to recognize a new battery? I can try another new battery in case the new one is not good 2) After 10 years could the control panel have gone bad somehow? 3) Could anything else be done besides having another $100 service call?

Not knowing what brand or model we're talking about, I can only suggest that some makes and models only retest the battery once a day or so. Often there are also fuses in the system that can fail if the battery fails in a dead short (which some do).

Sometimes when you buy a new battery it may not be fully charged. In some systems it could take it a day or two to fully charge the battery.

You could wait and see.