flat battery

Hi, I have a problem with the service indicator on my W209 CLK500. The car had a dealer "A" service 600 miles ago but last week the battery went flat after leaving the lights on.........:doh: It started again no problem after charging the battery but the service indicator now says the B...

W210 estate with flat battery. I have no key only the fob. I've read that there is a charging point (positive terminal) under the car where the passenger footwell is. Does anyone know where this is exactly? I can't see it with an inspection lamp. Can't get bonnet open to access the other charge...