plug polarity

I have a bought a battery charger that I will connect to a 110 volt supply.

The charger is from the USA and has a plug that will be cut off and a new
compatible 110 volt site plug fitted.

The power lead is a twin wire and the wire polarity is identified by a
series of raised lines which run the whole length. This is for identifying
either positive or negative. I need to know which one is which.

To help further the raised wire enters the existing plug on the side that
has the larger of the two pins.

If I haven't explained this well enough please ask me whatever other info
you need.

Thanks

fred