To reliably run an ebike for very long, you will need a voltmeter, and learn to use it.
ok i'll buy 1 tomorrow
Instructions that come with it should explain how to set it to test 20-200v, if not clear, ask us.
great thanks
Once you plug in a battery that is needing charging, the chargers green light should turn red, or somthing like that, indicating that charging is taking place. If it stays green, that means that either the batttery is charged, or that the DC wire between the charger and the battery is broken. Often this happens at the plug, could be the battery side of the plug or the charger side of the plug. Or it could even be inside the battery itself, or inside the charger itself that the connection is broken.
the charger is ok, its preform like you say
Once you have a voltmeter, step one is to probe the battery and find out what voltage the battery is at. If low, and the charger won't run, then suspect a plug or a charger defect.
i have this wattmater http://www.hobbyking.com/hobbyking/store/__10080__Turnigy_130A_Watt_Meter_and_Power_Analyzer.html is it good for test the battrey V?
Chances are fairly good, that you simply have a broken charger, or broken plug, and that is why the bike won't run. Chargers are notoriously unreliable, while the bike itself tends to do better.
As for looking at the plugs, one thing I have learned in 30 years of construction work, is that while 100% of people look, only about 10% SEE. Some just need glasses, others can never learn to notice the tiny details. Plug contacts getting bent aside or pushing back out can be very very very hard to SEE, despite many looks. I am one who sees, but I still have to look hard to do it. Only experience teaches you what exactly you are trying to see, that's the catch 22 of it.