When you setup a repeater you need to log into the remote access and the remote command console and enter the command "powersaver on".

The way these repeaters work is there is a logic processor (either ESP32 or nRF52840) and a LORA radio chip. The radio chip is always on waiting to decode the channel it's listening to.

The processor goes to sleep between packets. Afterall , there's nothing to do between packets.

So the radio chip will wake up the processor, the processor will decide to relay the packet or not and go back to sleep. This allows these repeaters to last weeks on a battery.