DC Polarity on Generators

Just made an interesting observation. Most small gennies have DC output as well as AC. DC output is via what I call a T pin plug, ie, one pin is horizontal and one pin is vertical and when you look at them they form a T shape. There is no hard and fast protocol for wiring pos and neg on these but the generally accepted format is horizontal is positive and vertical is negative (just like the negative, or earth, pin on a 240 three pin plug is vertical).

What I discovered is that the vertical pin on a Yamaha EF1000 is negative (falling in line with the comments above) but on a Honda EU20 the vertical pin is positive.

When you are making up extra leads for various purposes (battery charging, cig light socket etc) to connect to the factory lead be very careful about getting the polarity correct.