I must either drive my E350 daily or charge the battery at both go dead after a day or so. I have fruitlessly tried to find a short and so has a good mechanic I use. I charge by attaching a charger to the connections under the hood by the starter battery, which will, supposedly first charger the starter battery, then the main battery in the trunk. Suggestions welcomed!

 

If you go on YouTube, there is a channel called "Pine Hollow Auto Diagnostics" and he does a lot of work on amp draws and kill batteries. A few tools required and he shows you how to find the issue. Most of the time it is a faulty component that is not letting the CAN fall to sleep. Check it out.