hey Jon, for what it's worth I have had some battery issues with my 85' 190e. My commute is 9 miles through Beantown that takes about 40 minutes. the car never gets up past 30 mph. pretty rough on the battery I have been told. So I got stuck in REALLY bad traffic the other night and after getting out of it, parking the car, waiting fifteen minutes, and going back to it I couldn't get it started, got AAA on the scene, a jump, and was on my way. Since then it's been freezing up here, also not good for the battery. And the car has given me problems if I let it sit in the cold for the entire weekend without riding it. I never take it anywhere but the commute, your riding the interstate was probably the best thing you could do for the battery. My answer to the issue was to go out and get a trickle charger (needed one for the bike anyway). you might consider it for 30 bucks or so. That way if you don't have time for the super slab you can just pop the hood and hook one of these up in the garage, let it go over night (get an automatic one so you don't have to watch it or time it) and fagedaboutit. Mine has new battery and alt. I have been told that the combination of the commute/need for defroster (a/c might be on)/ lights/ winshield wiper for the snow.../ rear defroster/radio and cold energy sapping weather are just a little too much sometimes. trickle charger.... that's my 2 cents.
best of luck,