Roadtrek Chevy Express Chassis Battery Draining While Unplugged

[Sensfan-ClassB]

Last summer, on two occasions, our 2011 Chevy RT truck battery lost its charge after a only few days of boon-docking. Both times, the battery was successfully boosted. We finished our summer trip and returned home. I had the battery tested and my garage said it was good. We plugged in the van outside where it passed the winter months (as usual).
This spring/early summer, the van has remained plugged in, except for its monthly runs to exercise the motor, etc. Recently, I unplugged it from the house electricity to check the battery status (3) of the two 6V AGM cabin & the truck. The cabin batteries were/are fine, however the truck battery discharged again as it did last summer. I checked to see if had left something on that could have been draining it. It appeared that the dome light may have been in the on position, so I closed it and reconnected the van to the house electricity. The truck battery recharged.
The other day I again disconnected the van from the house electricity to see if the truck battery would hold its charge. Today, with the van still disconnected, I discovered that the truck battery had discharged again. Here may be a clue as to what’s going on ...when I opened the cabin side door, my dashboard activated showing the mileage, and, my scanguage temporarily displayed values, then, everything turned off after about a minute, first the dash then the scanguage. When I opened the door again, the same thing happened. FYI .. the intermittent scanguage truck battery charge readout indicated 9.8.
Then, after I plugged the van into the house electricity again, the above mentioned door opening related dashboard and scanguage activity stopped.
I’m guessing i may have a DC short?, however, being a non-tekkie, I would appreciate any feedback.

 

[booster]

Re the Scangauge part of all this, I have a discussion on the forum about that problem as it has bitten me in the past. Ours is a Scangauge2 so can speak for others.

If the Scangauge power is completely removed by either disconnecting the starting battery or uplugging it from the OBD socket, when it is plugged back in or the battery reconnected the Scangauge lights up and says "connecting" but it never connects and does that until the battery is dead. The Scangauge needs to see the system in key on (doesn't need to be running) to connect and go into normal use mode hibernation.

If you had a dome light kill the starter battery, it probably would have put the Scangauge into that loop and rekilled it.

The dash coming on isn't normal, but if the voltage was really 9.8v it may have been an error warning of low voltage like a "check your gauges" display or light.

Time to get a trickle charger for starting battery or a jumper for the separator when in storage?

 

[Sensfan-ClassB]

Thanks Booster. Ours is also Scanguage 2; I’ll provide an update ASAP.

 

[TX-Trek]

As far as I recall, the odometer coming on for a few seconds is normal at door open with key out.
I think you'd have to check for a parasitic draw at the fuseblocks (engine/under-seat) with all modules "asleep" and the van thinking all doors/hood are latched.

This may help to check wiring diagrams. I took a quick look and there is some interface between cluster and BCM/ECU, with considerable inputs from a variety of sensors, latches, etc. One of those can cause the draw.

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[Sensfan-ClassB]

Thanks TX.
I hope to know within a few days whether or not the historic parasitic truck battery draws related to my Scanguage 2 per Booster’s feedback. If it appears that they were not, I will have someone check the fuseblock, per your feedback.
Would that someone need to have previous knowledge of Class B electrical systems, or could the average auto electric shop conduct the detective work?

 

[TX-Trek]

Unless you've got the cabin battery switch on, the chassis (engine) battery should be isolated from the cabin. Then that turns into a basic Chevy express electrical diagnosis.

That level diagnosis should be able to be handled by a good shop familiar with GM electrical, which in this case is very similar to GM trucks as well. A basic diagnostic involves a voltmeter measuring amperage draw between positive battery cable and battery positive with vehicle awake and asleep. Sleeping draw should be no more that 10 milliamps if I remember right.

In my own research of similar parasitic issues, I've found trouble spots to be the electronic compass module, door latches and for weird problems, the position of wire harness directly below the ECU. It runs over the driver side control arm and can rub through over time if its been resting on the control arm.

 

[booster]

Roadtrek did do some rewiring of factory stuff to put things onto the coach control. I think some vans the dome and map light type stuff is that way. The big thing that messes up parasitic checking is all the timers that keep the radio and such active for a while after the key is off and the door closed. You wind up waiting a lot for all to time out.

 

[Sensfan-ClassB]

… "Time to get a trickle charger for starting battery or a jumper for the separator when in storage?"

I am gong to buy a quality solar unit that turns itself off when the battery is fully charged. Assuming that the RT’s only problem is a parasitic draw, roughly how long may it take the trickle charger to bring my truck battery back to full charge from its present discharged state?

 

[TX-Trek]

Some things come to mind, maybe worth noting....

1. Root cause of parasitic draw should be prioritized and corrected. I realize you need to ensure starting in the meantime.

2. Booster noted that it may take a bit of time for vehicle modules to go to sleep. Doors should be left open with latches manually flipped so ECU thinks doors are actually closed. This allows access into the van to check underseat fuseblock without waking up the vehicle. 2010 and 2011 don't have a lot of modules so sleep time should be minimal.

3. What will happen - with volt/amp meter connected between positive cable and positive battery lead - is that you will first see (as example), say 25 amps when vehicle is first shut off. As modules and eventually ECU/BCM shut off (sleep) that amperage will start to drop, eventually reaching sleep state milli-amps. If by 30 minutes meter is still showing anything over 10 milli-amps thats your parasitic draw. Now you start checking draw across each fuse with another voltmeter to see which circuit is still active. That would be the underhood and underseat fuseboxes, which is why you manually latch hood/doors to be be able to access underhood and interior without waking up the vehicle. You don't want a charger connected when doing this. When a fuse draw shows almost matching amperage to the overall amperage draw, pull it. If overall draw drops, thats your parasitic drain and you can see which circuit that is.

4. Battery may need to be charged with a charging unit designed to provide the higher amperage needed for a discharged state battery. As the battery charges, the amperage draw will drop, then a maintenance trickle charger is suitable. Some trickle chargers don't have the capability to recharge a significantly discharged battery.

5. If battery/engine/chassis grounds have never been maintained I suggest unbolting each ground point, cleaning and reconnecting. Grounds may look ok but contact point corrosion is hidden. Very important that the negative side have a clean path.

The link I sent on vehicle manuals should have wiring diagrams with ground locations.

 

[Sensfan-ClassB]

Thanks again TX. Your valuable information will be given to the TBD technician. I do believe that it would be best if I can find someone who is familiar with my generation of RT. I’m going to give Mobilife RV Centre in Kitchener, Ontario a call. They have serviced mine over the years.

 

[TX-Trek]

Hope it all works out. Remember also that you've got 2 general electrical systems: the chevy express van and the cabin/rv outfitter part. Isolated from each other by the battery separator. Although I think the macerator is hot 12v at all times.
Checking the van electrical should generally be standard GM stuff.

 

[Sensfan-ClassB]

Understood. I have secured an appointment at Mobilife in Kitchener later this month. The manager responsible for the electrical section was employed at the Roadtrek factory when/where my RT was put together. I do believe that he was directly involved in designing vehicle electrical systems

 

[Mardeldelmar]

Last summer, on two occasions, our 2011 Chevy RT truck battery lost its charge after a only few days of boon-docking. Both times, the battery was successfully boosted. We finished our summer trip and returned home. I had the battery tested and my garage said it was good. We plugged in the van outside where it passed the winter months (as usual).
This spring/early summer, the van has remained plugged in, except for its monthly runs to exercise the motor, etc. Recently, I unplugged it from the house electricity to check the battery status (3) of the two 6V AGM cabin & the truck. The cabin batteries were/are fine, however the truck battery discharged again as it did last summer. I checked to see if had left something on that could have been draining it. It appeared that the dome light may have been in the on position, so I closed it and reconnected the van to the house electricity. The truck battery recharged.
The other day I again disconnected the van from the house electricity to see if the truck battery would hold its charge. Today, with the van still disconnected, I discovered that the truck battery had discharged again. Here may be a clue as to what’s going on ...when I opened the cabin side door, my dashboard activated showing the mileage, and, my scanguage temporarily displayed values, then, everything turned off after about a minute, first the dash then the scanguage. When I opened the door again, the same thing happened. FYI .. the intermittent scanguage truck battery charge readout indicated 9.8.
Then, after I plugged the van into the house electricity again, the above mentioned door opening related dashboard and scanguage activity stopped.
I’m guessing i may have a DC short?, however, being a non-tekkie, I would appreciate any feedback.

Hi there, this is pretty random, but my batteries were draining at an alarming speed and I discovered that the lighting around the vanity mirrors on the sun visors were staying on because the springs had lost their strength. You could not see it during the day but at night there was a faint glow around the mirrors when I put up the windshield night cover-

 

[teslasmuse]

I noticed I can hear the system checking like booster mentioned after I shut the engine off and until I open and close the driver side door before setting up for boondocking. That seems to help. I had a new stereo installed and it killed the power modulator thingy behind the stereo and it was killing my Chevy battery really fast until I unhooked the stereo. It was power cycling constantly. I still need to take it back to the shop to have it replaced, I was a couple of states away at the time.