How can we reverse the polarity?

As the unit has arrived with me, I wanted to try it right. Batteries pure, pressed the button and nothing !!!
There were new ones, yet just happened nix. After I screwed the headlamps apart, I have seen the positive and negative poles reversed were soldered on the board !!
Actually, this should not happen, yes!
So, get the soldering iron to the error corrected.
Now he works.
Because the error gibts a star less
The lights and the laser beam are well lit and make sure that you will be better seen at night.
I can only recommend this tail light.
But I hope that this error only a single case was with me.