I call bullsh$t! The donor car's alternator does have a voltage regulator. So the voltage will not exceed 14....v, The current on the other hand will spike but devices only draw as much current as they need. One dumbass from RMI actually said it can cause a surge of 300v....wtf???? Dude your...
The water itself and the piping should create a decent earth? But on the other hand, I have lived in a house where I could feel a slight hint of electricity passing through my fingers when taking a shower... scary!
I have done it successfully - very cheap. Here are my steps and gradual improvements:
parts needed: 20MM class 6 water pipe (from local agri store about R4.50 per metre, I used about 85 Metres.), fish pond or any pump with lift of at least 5m and running about 2000L/h. Timer or in my case...