And what if the supply develops a short between primary and secondary sides?

 

I do not encourage this thread.
Though Max supports it, I do not.
There are dangers involved in doing this.
I know there are SMPS that can be connected in series but I will not do this with ATX PSU's.
The fact that the secondaries need to be properly loaded to regulate all voltage Buses and the fact that OP has no idea what he is doing I do not agree that we must encourage doing this.
So I am ignoring this thread after reporting it.

 

I actually desoldered the wire from the main's earth, much easier than isolating the pcb from the case. This was just an experiment, I am aware of the dangers involved in this and after playing with them they have gone into the trash can.
I need a way to power 3 battery chargers from isolated power supplies so that I can charge 3 batteries in series without separating the cells and transformers aren't cheap.

 

I think you should draw a circuit, so our members has common pictures to discuss, and it is more easy is to find out where the problem is.