In response to al_aizad, a voltmeter can be used to check the charging system of a scooter/motorcycle.
By checking the voltage across the two battery terminals .......
i) when the engine is stopped and ignition off
ii) when the engine is running but at idle revs
iii) when the engine is running at higher revs (usually around 3000 revs or more)
you can assess the condition of your battery, your regulator and your alternator (stator in USA).
Have a look at the attached diagram
http://www.electrosport.com/media/pdf/f ... iagram.pdfand it gives some idea of what voltage you should expect to see at each of the 3 above states. The diagram is a bit complex in parts, but it will help you check and diagnose charging faults with any bike/scooter.
Some bikes (eg Kawasaki ER500) are notorious for regulator problems which cause hundreds of pounds worth of damage when they go wrong, so it is worth checking occasionally with any scooter/bike.
Having a voltmeter attached to your handlebars on a PCX may be a bit OTT though, as I have not heard any problems associated with failing charging systems on the PCX. I usually check mine once a month or so.
Hope this helps!
Tom.