Battery Boosters...

[ACEngineering]

If you don't get a good connection it won't switch itself on. In the same way you can switch it on and touch the 2 clamps together and they are both dead.
It needs to read some sort of voltage to establish the polarity is correct before the clamps become live

Yeah I know that now, hardly ever have use for one imo that's why it's taking so long to find something else to test it on.
Once I know it works I could sell the spare one that's only ever been out of box once just to check it was okay and charge it up.

 

[Grassman]

Another noco here. Best tool in workshop

I thought you said you were the best tool in the workshop?