To be Idling or Not to be Idling?

I went out to work on the Airstream in storage the other week. I typically pull the batteries during winter storage, but I didn’t this time because we were gonna take a quick winter trip (that didn’t pan out).  Actually, to be completely honest, I didn’t bother pulling the batts because I don’t get any more longevity out of them whether I go thru the hassle of storing them on a Guest 3-stage charger, or not.  To the Battery Guru’s who may be reading this: flame away.

I digress. So, the batts have been sitting, no maintenance charge, for about 2 months. I decided to back the E-350 up, plug in the 7-way umbilical, and let her idle to charge the batteries while I worked.

It idled for about 2 hours. All gauges were normal.  I’ve seen this van put as much as 15 amps back to the batteries- pretty good for tow vehicle trailer wiring.

Fast forward to my next fill up. The van is our daily driver, typically get between 16-18 MPG. Well, the “idling for 2 hours tank” came back with 13 MPG.  I was really surprised.

I know “idling” and “efficiency” when talking MPG is sort of an oxymoron, but I guess what I mean is I thought it wouldn’t burn as much fuel.  Stoichiometrics of diesel engines, and all…

After a little research that included a discussion with an actual diesel mechanic responsible for a fleet of 200 vehicles ranging from bulldozers to Class 8 trucks; it appears idling is not recommended.  “Wet stacking” being the primary reason.  This is a condition in the cylinders where due to lower combustion temps and incomplete burn, the fuel washes down cylinder walls and adds to fuel in the oil which in turn causes accelerated wear on all oil lubricated components.

So, for charging the batteries, it looks like a dedicated generator is best.  Besides, a Yamaha EF2400IS is much, much quieter than my E-350.

See you Down the Road!