Bad batteries have never really damaged a PS-1 board. Just can cause a software scramble, which can occur with a BCR if you forget to let it charge fully and try a direction change when it is only at 3-5Volts. Only about 1 % of the PS-1 boards I have worked on had a battery related hardware fault. Usually motor over current can burn a trace, or rectifier diodes go bad.
I am not convinced bad batteries kill PS-2 5V boards either. I have seen plenty with old batteries that still start up and run fine once the battery is replaced.
There are rectifier diodes that short, a power fet that can short, processor can go bad. It is old and complex, but as John stated plenty still run fine regardless of whether they were early Rev G or Later Rev K boards. But there are some models that that seem to have a much higher failure rate, Like the FEF Northern, and the r17 Redbird subway. So maybe those batches of boards had some substandard components.
The PS-2 3V was a much more robust design, and also can come apart so it is easier for component repairs. G
