If do not have enough “known good” Zigbee Router devices then will drain the Zigbee device batteries, this is because if the reception is poor then devices will need to resend its messages over and over.
You need to have enough “known good” Zigbee Router devices and even then Aqara devices (and Xiaomi devices) are very fussy plus have known issues connecting to closer/better Zigbee Router devices unless you manually re-pair each and every Aqara/Xiaomi device after you added additional Zigbee Router devices.
Read and try to follow all the generic tips here about avoiding interference and adding good routers, it also contains to specific mentioning about other known issues with Aqara devices (and Xiaomi devices):
Also see link there to another thread that specifically has connection tips about Aqara/Xiaomi devices:
In summery; Aqara/Xiaomi have buggy firmware so you do need workarounds and jump some hops.
PS: Also note the battery discharge curve(s) for litihum batteries is not same as for other battery types:
