Crazy Theory About Draining of Coach Batteries

[chasfenwick]

Throughout the winter, typically my 2017 Precept 31UL would sit in the storage lot for ~3 weeks, with Master Switch definitely turned OFF. On three such visits to check on it, the coach batteries were nearly dead - between 3vdc and 6 vdc. What could have been draining them? Fast forward to 2 weeks ago. It appears that the F53's under-hood light had been ON since we took delivery last November! I didn't even know there was such a light. Could it be that that light is on the same circuit as the electric steps, energized when the Master Switch is OFF?

[bansai]

I think the best approach is to make 100% sure your disconnect completely isolates the battery or it's useless. Install your own for less than 10 bucks and never worry about it again.

[TWP723]

The hood light is turned on and off with a plunger switch in the engine compartment. The switch may be bad or need adjusted. Most of Ford's hood lamp switches are adjustable. Not sure on yours. It is not on the same circuit as the steps. It gets power from the vehicle battery, not the house battery.

[chasfenwick]

I hate to disconnect the batteries unless absolutely necessary. Twice with my Melbourne the batteries were disconnected and the spark zapped the buried in-line fuse for the control/display unit in the center of the dash. So I'm more interested in understanding what I've got than I am in implementing a workaround.

[chasfenwick]

This hood light has a manually operated switch as part of its mounting base.

[TWP723]

Originally Posted by chasfenwick

This hood light has a manually operated switch as part of its mounting base.

Manual? WTH? It should be a spring loaded hood switch. Kinda like the courtesy light switches in the jamb of a regular vehicle. That's a new one on me, and quite honestly, weird. You only need the hood lamp with the hood open, so why a manual switch? Ya know..? And a lot of them also operate security systems. Hmmmmmm....

[wags999]

Originally Posted by chasfenwick

I hate to disconnect the batteries unless absolutely necessary. Twice with my Melbourne the batteries were disconnected and the spark zapped the buried in-line fuse for the control/display unit in the center of the dash. So I'm more interested in understanding what I've got than I am in implementing a workaround.

You should install a switch which you turn off...never have to touch the battery...

[Vicr]

This has been talked about before. With the master switch off disconnect the positive lead from the battery that goes to the converter. Put an amprobe between the positive post on your battery and the lead to the converter. If you see current draw on the meter have some one remove a fuse at a time from the converter until the amprobe shows a drop in current. When ever you see a drop in current you know the devices on that circuit stay on with the master switch off. Do this until there is no current draw. Next winter when you store your rig pull those fuses out. Another solution is to install a battery disconnect switch in line on the positive battery lead to the converter. It's always a good idea to use a battery maintenance device on the batteries as well. Battery Tender and NOCO Genius are excellent units to use.
Vicr
IBEW Local 46
Seattle WA

(I'm an electrician)

[Vicr]

Blue Sea Systems make an excellent battery disconnect.

[bankr63]

Originally Posted by chasfenwick

I hate to disconnect the batteries unless absolutely necessary. Twice with my Melbourne the batteries were disconnected and the spark zapped the buried in-line fuse for the control/display unit in the center of the dash. So I'm more interested in understanding what I've got than I am in implementing a workaround.

A properly designed battery disconnect switch should not arc when switched on and off. You can actually count on it to isolate your circuits when you do have to disconnect your battery (for changeout). Presumably the arc you got on disconnecting the battery was because loads were still present on the system.

[chasfenwick]

Both my Melbourne and my Precept were designed such that there are still "some" loads on the system when the "Master Switch" is OFF. I have assumed that those loads must be way down in the milliamperes range to be of no consequence. It does seem like an odd way to design an electrical system. What is the "Master Switch" supposed to be FOR, anyway?

Lexus had an embarrassing problem when they first introduced the LS400. The receiver for the door locks drew so much current that people leaving their cars at the airport for a couple of weeks, for example, came back to a dead battery. This led to a recall! (My car was one of those).