Battery Disconnect Confusion

Mechanic install a blade disconnect?
That’s not any more difficult than hooking or unhooking the battery.
That works, but it’s a band aid for the real problem on a basically new RV. To each their own.
I’d solve the problem, not hokey rig it.

I just learned something , I just asked someone re your problem.
Ask your mechanic to put a clamp volt meter onto the battery feed wire to the alternator .
A bad diode rectifier inside the alternator could be allowing battery voltage to drain back into the alternator when the vehicle is off .

The diode should be acting like a one-way valve to allow voltage to charge the battery but if its gone bad, then it allows a two way flow. That could be your problem and its something to eliminate if it is.

I would try to figure out what is drawing the battery down and fix that. ie: If you have a dome lamp switch on the dash that controls a dome lamp that has its own remote switch, make sure the dash switch is not left in the on position.

bobndot wrote:
I just learned something , I just asked someone re your problem.
Ask your mechanic to put a clamp volt meter onto the battery feed wire to the alternator .
A bad diode rectifier inside the alternator could be allowing battery voltage to drain back into the alternator when the vehicle is off .

The diode should be acting like a one-way valve to allow voltage to charge the battery but if its gone bad, then it allows a two way flow. That could be your problem and its something to eliminate if it is.

I have no idea what this means, but I have printed it out and will talk to the fix-it guy. Thanks!

Krusty wrote:
I would try to figure out what is drawing the battery down and fix that. ie: If you have a dome lamp switch on the dash that controls a dome lamp that has its own remote switch, make sure the dash switch is not left in the on position.

How can I do this?

The chassis battery is drained by the computer (ECM). There is nothing that can be done to stop this besides disconnecting the battery or installing small charger to it.

^Yes, to an extent, but the OP never said how long it took to die.
But alluded to the fact that he was concerned about camping for a week or 2. So making preemptions off of a not so detailed description of the problem, I’d say it dies in a week. That is not normal parasitic discharge.

But who knows what the real story is. I cannot imagine a 2018 anything needing a “fix it guy”. Is it really out of warranty? Or is there more to the story like I first alluded.

People could get much more help, presuming that’s what they want or they’d keep their story to themselves, if they told the WHOLE story.

On our moho the chassis battery also powers the electric steps. There is enough of a drain that I disconnect the chassis battery when not in use and regularly put a battery charger on it to top it up before doing the disconnect.

I discovered this by leaving the battery connected and with the various small loads plus the electric steps the chassis battery was drained in 30 days.

RambleOnNW wrote:
On our moho the chassis battery also powers the electric steps. There is enough of a drain that I disconnect the chassis battery when not in use and regularly put a battery charger on it to top it up before doing the disconnect.

I discovered this by leaving the battery connected and with the various small loads plus the electric steps the chassis battery was drained in 30 days.

I am right there with you. That is my experience and solution with our 2007 Phoenix Cruiser on a 2007 Ford E350 chassis.

When out traveling, we don't stay in one place for 30 days without driving the rig, but the scenario is true at home.

I am not anal about it, but I recharge house and chassis batteries at home roughly every other month. The chassis battery is disconnected, the house batteries remain connected. They recharge to full fairly quickly which implies they are not suffering during extended non-use periods.

enblethen wrote:
The chassis battery is drained by the computer (ECM). There is nothing that can be done to stop this besides disconnecting the battery or installing small charger to it.

I'm not debating your post, I'm not a mechanic but I think its a very low draw. It seems to take a lot of time to do that. The knife blade is a good idea long term IMO .

My only reason for thinking that is that I park my 2018 Ford for 2 weeks multiple times during the winter, unplugged from shore power and my chassis battery has never dropped below 12.5v.
I have it on a digital volt meter which I activate each time to view a reading.
I bought one of those 1.5 watt solar dash panels because my truck has a 'hot' 12v outlet to accept the little charge that panel offers. It maintains my chassis battery at 12.6v for the same 2 weeks or more period . That battery went from 12.5v to 12.6v's using that little panel.

Just an uneducated guess but if that tiny panel keeps a chassis battery topped off I would think the draw while parked is very low unless there is another underlying problem somewhere.
In the OP's case, a bad alt diode would not show up as a blown fuse anywhere but would cause a significant battery draw while parked as it was explained to me. Being that the alt will work fine while driving to charge the battery its in the parked mode where the problem might be, someone would never know there was a problem until there battery was dead from sitting parked. Just something to think about to try to help him resolve his problem.