Is 13v from 12v (>10%) too much? I am wondering if these chinese units are acceptable or do I need to look for better ones.
Hard to say without knowing what the application is - cheap wall wart PSUs are often rated at +/- 20% (since that's about the level of regulation you get out of a transformer). Stuff that's designed to run devices directly might be +/- 5%. A good quality PSU might be +/- 1 or 2% with 0.5% line and load regulation.
Does the device have a regulator? If so, what regulator? Look up the spec of the regulator and you'll have your answer.
Sadly the specs are not disclosed. I assume as it is an expensive item, it uses a high quality power supply. The replacement ( I did not get any power supplies in the liquidation) supplies I found don't seem to be acceptable imho
^This^ Its quite difficult to give accurate tolerances without knowing what the device is....for instance I once worked with a highly specialised TIG welder that used a one of a kind power transformer that had tolerances of +/- 0.0004 and would simply not work with anything else.
