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.

The CPU serial connector is ruled by the BIOS on the CPU/HWY card. A battery off/power down is the only way to reset it. That's why back-ups are so important.

Yes, backups are essential. I like to date and store them in various places as well as the laptop, such as the U drive at the shop, USB drives.