weekend in Gary yard

That all depends on the load you are putting on the batteries while sitting there.
If you don't have an APU and are watching a TV or using a computer, have a 12v cooler, or other such load, then 30 minutes for each 3 hrs would be enough. If you are not using any appliances, then you wouldn't need to idle to charge the batteries at all.

 

Well, your APU should charge the batteries, so there would be no reason to run the main engine. I am assuming you were running the A/C from the APU.

 

Maverick trucks have EPU units (electric power units) to run the bunk heat, AC, plug ins etc. powered by 4 batteries. There are 4 separate batteries for the truck, so the engine starting won't be affected if the EPU batteries get low. When the EPU batteries get low there will be a beeping sound and the lights in the bunk won't work. I've been informed to idle for about 2 hours (cruise on, hit accel to bump idle to 900 rpms) to fully recharge the batteries.

 

Hey saltwaterm, do me a favor and run up to Zantes and Fed-X me a Gyro!

 

There are plugs at Gary that you can use. (Or there were the last time I was there) on the backside of the shop near the fence. Get yourself an extension cord and plug in. No need to idle.