Battery is not charging enough to start bike

[schwilling]

Ok Thanks for reading I am new to the forum had the 2006 GS250 for about 6 months I bought the bike used with 1800 miles now I have around 7000 miles. Problem is that I am having issues starting the bike. It  seemed like a dead battery so I have tried to charge the battery but had same issue so I replaced the battery and spark plug, was able to get the bike to start but after driving for about 20 to 30 minutes I try to turn over the bike and get no lights like the battery is dead. If I hook up a charger the bike starts like normal. What on the bike charges the battery when running and could this be the issue why everytime I go to start the bike the battery seems dead. So I am able to start the bike when external battery of some kind is connected but battery seems drained after each ride

[motorstar rider]

you might have a problem with your regulator/rectifier that black box w/ heat fins behind the rear left side fairing, its job is to convert AC voltage from your stator to DC voltage (rectifies it), then maintain its output to 13+v to 14+v to keep the battery constantly charged (regulator part) when engine is running, if its leaks current then it will drain your new battery overnight or a few hours...check also the connectors for loose connections...hth

[250gs]

good point msr, I noticed the battery (red)light on my bike dash was flickering a bit - but only on idle.
 Later I took  the seat off and checked the electrical connectors and found that the regulator connector was unplugged. Plugged it back in and all ok.

[drummerben]

yeah, I recently had a similar problem. I replaced the r/r and all ok.