Electronic Alarms and Home Security Devices - Smoke detector weirdness

This morning I awoke to the once a minute chirp of the smoke detector. This detector is connected to several other detectors and they are all powered by AC and 9VDC battery backup. The instruction sheet for it says this chirp indicates low battery. So I installed a new battery and it still chirps. I pushed the test button causing the alarm to signal briefly as described in the info sheet. Still the detector chirps once a minute. No phone# to call the mfg. What's the consensus? Can it be replaced with another mfg or do all 5 need to be replaced at once? Does anyone know if they all use the same connctors. House is only 3 years old, detectors have 5 year warranty but need sales proof which I do not have.

Checked the breaker for that (normally) dedicated circuit?

There are several models that also chirp when the detection chamber is contaminated (in some the LED telltale blinks a specific code...).

For the most part, the recent models of consumer grade smokes like this are pretty interchangeable. If you can get the same brand, it's generally a good idea to do so.

Check that battery, sometimes you get a bad one out of a brand new package, but otherwise, just replace the darned thing. You will expend far more effort trying to claim a warranty claim on an $25-30 smoke detector.