The trip was unexpected. I have had the car for only 2 weeks. Thus, I had not yet had time to plan out power sources and cabling yet. The car is a Mercedes-Benz GLK350. GLK Stands for (translated) Off-road, Luxury, Compact. Not exactly a car where the drill comes out and holes are freely made in convenience. I figure patience and planning is the key. In principle I want a power supply which is stable during engine start (good luck) and on a timer after the car has been shut down so that APRS “finishes” it beacon sequence and the radios are available for a few minutes during stop and go. Hence, our cars has the typical inline, with Anderson PowerPole timing 15 minute timing unit. Perfect! It senses alternator voltage and turns on the power to all the toys listed in the -1 post. 15 minutes after the alternator stops (charging voltage lost) the power is shut off.
The MB has a emergency battery (12v 20Ah) for the brake system conveniently located in the trunk of the car. Perfect place to take power! Or maybe not. On the first leg the radios keep dropping off line momentarily (power on sound). Is it a bad connection? No, the MB aux battery charger is actually reducing the charging voltage from the alternator when a certain charging state is achieved. There goes the electronics!
The rest of the trip I had to place the sensor in override manually at the beginning of the day and off for the night.
The fix – I need to move my cable from the emergency battery to the source terminal of the e-batt charger. This is a little tricky since the charger is located in a tight area. More to come.