I was testing some spare Adix CPUs in the shop along with batteries. One CPU after a day had no communication via the serial port. I tried a reset, power down, pulled the CPU and reinserted (with the battery connected), same. Only after pulling the battery and defaulting was I then able to communicate with the CPU. I wonder if there's anything else I could have tried?

Re: batteries - stock 3,6v cordless phone batteries will connect to the CPU without having to connect the original connector, but unlike that connector the stock connector can be connected upside down.