The 2003-2006 R230 series seem to have a problem with the BCM (Battery Control Module) as start an electrical fire in the trunk. Very common issue and a safety hazard - this is what happened with my car. Vehicle has dual battery, starter in front, convenience battery in trunk and fuses that operate at 130 Amps - the BCM capacitors and circuit board age and at some point can no longer handle the high current and catch fire.