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Old 10-20-2021, 05:51 AM   #1
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Troubleshooting a dramatic change in battery draw

We had an “event” earlier this month with our 2020 Interstate 19 Tommy Bahama. I discussed it in this thread:

https://www.airforums.com/forums/f24...ng-228072.html

Everything (minus the A/C) is functional, and we are getting the A/C replaced down in Ft Myers FL in early December.

However… we’ve discovered a major change in battery drain since the incident. We spent a month on the road in August / September, a decent amount of the trip was boondocking without shore power. We were frugal in our battery usage but never had issues running the fridge overnight on low power. We even had the heat on a few nights while in Tetons / Yellowstone.

Now, even after driving for 5 hours we don’t seem to be seeing the batteries getting to the charge level we were used to. It seemed like it would get to ~80%, maybe around 13V. Now we are lucky to get to 60%. And then it goes down fast and hard.

I found this very helpful for understanding the scope of stealthy draw that is likely happening in the van:

https://www.airforums.com/forums/f24...es-158324.html

Any other tips on troubleshooting this? I have the breaker turned off for the A/C, though I don’t think that would have an impact on the DC battery drain in any case. We keep the Magnum inverter turned off. At the most we have the fridge running, some USB charging (though not even that over night), and one set of lights on from time to time.
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Old 10-20-2021, 06:00 AM   #2
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I’m not the best advice you’ll find here, but it sounds at first blush like your battery has been seriously depleted and now will not hold a charge.

Good luck.

Maggie
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Old 10-20-2021, 07:34 AM   #3
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^
YEP
First thing to do...
Do you have a stand alone charger?
DISCONNECT the battery, fully charge, let it sit for several hours, reinstall, turn stuff on and watch the battery monitor.


'Letric will find the path of least resistance and it may very well be damaged wiring from the AC disaster that is causing the high drain. Does the AC have a stand alone fuse/breaker? Make sure it off/out.

Bob
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Old 10-20-2021, 06:27 PM   #4
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Originally Posted by ROBERT CROSS View Post
^

'Letric will find the path of least resistance and it may very well be damaged wiring from the AC disaster that is causing the high drain. Does the AC have a stand alone fuse/breaker? Make sure it off/out.

Bob
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Thank you both. Good ideas and we’ll give it a shot.

I did cut the breaker for the AC. Sadly, the fuse for the AC is the same as the fuse for the C-Zone control system 🤷*♂️.
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Old 10-20-2021, 11:20 PM   #5
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Quote:
Originally Posted by CavemanB View Post
I have the breaker turned off for the A/C, though I don’t think that would have an impact on the DC battery drain in any case.
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Originally Posted by CavemanB View Post
I did cut the breaker for the AC. Sadly, the fuse for the AC is the same as the fuse for the C-Zone control system 🤷*♂️.
Under normal circumstances, AC & DC power doesn't crossover, so you are right to say that "I don’t think that would have an impact on the DC battery drain". But this isn't a normal circumstance. So first things first - turning the AC breaker for the A/C is good start.

You have not posted any detailed pics or given much details on the previous mishap in as far as how extensive the damage (yes, I read that thread). So if I am to assume the worst case scenario - you have lots of wires that got pulled, stretched, kinked, nicked, whatever else that could've damaged them.

In the context of what in the A/C system can cause that DC drain? Well, there are really only three +12VDC points that links the A/C system to the DC fuses. All of them go to the Dometic RVC Interface in your unit. Don't ask me where or how to pull them out coz I do not have an AI19. I am getting this info from the AI19 schematics but they do not specify its physical location. I can only assume they have to be very close to the A/C itself or even inside the ceiling cavity opening. And I can also confirm from the schematics that as you said the CZONE is part of that Ckt. #8 (7.5A) GRY. where the Dometic RVC Interface is also connected to.

There looks to be 4 connectors behind the Dometic RVC Interface. 3 of them have +12VDC (red, red & wht). The 4th connector going to temp sensor does not. So honestly, this is grasping at straws -but- theoretically it is possible that if your Dometic RVC Interface got damaged, then it could be drawing constantly. It is normally an intermittent draw device. So if you disconnect all 4 connectors, that completely removes any A/C components from the +12VDC side of the coach.

That's pretty much all I can find in the schematics that links your A/C to the +12VDC.

Good luck.
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Old 10-21-2021, 05:59 AM   #6
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Originally Posted by Alex AVI View Post
That's pretty much all I can find in the schematics that links your A/C to the +12VDC.

Good luck.
Thanks so much Alex. I *think* I properly disconnected all the DC components on the roof (and capped / sealed the ends) but I’m definitely going to re-check when I arrive in FL and have access to a ladder again.

I read the “recovering from a deep discharge” section in the Lifeline battery manual. It discourages non-professionals from doing this, and gives these instructions:

Quote:
1. Stabilize the battery at 20-30°C (68-86°F) for at least 24 hours. 2. Charge at a constant current of 5% of rated (24 hour) capacity until the voltage reaches 2.58 VPC (15.5 volts for a 12 volt battery), then continue charging at this rate for an additional 4 hours. Note that the charging voltage may get as high as 3.0 volts/cell, so the power supply must be capable of outputting this level to maintain constant current. This constant current charge may take 16 to 20 hours.
Is it unwise for me to try this on my own? Any additional device?

Seems like I need to get this taken care of regardless of the status with the AC.
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Old 10-21-2021, 06:15 AM   #7
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When the a/c unit struck the overhang, did any of the wiring harness get pulled tight?

Just thinking that perhaps something not specifically related to the a/c got pulled tight enough to cause a short.

If you're discharging more quickly than you used to, then obviously the power is going somewhere. If everything is turned off or disconnected that leaves a short as the possible culprit.
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Old 10-21-2021, 09:59 AM   #8
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Originally Posted by CavemanB View Post
Thanks so much Alex. I *think* I properly disconnected all the DC components on the roof (and capped / sealed the ends) but I’m definitely going to re-check when I arrive in FL and have access to a ladder again.

I read the “recovering from a deep discharge” section in the Lifeline battery manual. It discourages non-professionals from doing this, and gives these instructions:

Is it unwise for me to try this on my own? Any additional device?

Seems like I need to get this taken care of regardless of the status with the AC.
CAVEMANB - I think most manuals have the typical 'blurb' about leaving everything to professionals as their CYA. Having said that, it would be up to your comfort level - if you are comfortable tackling it and take the proper precautions when dealing with 'live ammo' , then I see no downside to trying. That's assuming you can satisfy those parameters set forth in their procedures you outlined.

Short of going to the dealer, which I assume is not feasible right now given they can't fit you in until Dec and you are away from home base, you have few choices but to (as you said) "get this taken cared of",

My take on it is pretty much same as what everyone seems to agree on - that the drain is not normal and the cause could be:

1. There is still an un-resolved short. This could be a wiring short or damage within a certain component (like the Dometic RVC Interface).

2. The batteries got drained to the point of damaging their ability to retain max. charge.

3. It is entirely possible this is completely unrelated to the A/C damage and just a coincidence.

The A/C mishap is an easy target to blame because of the obvious cause & effect timestamps happening very close to each other. So even though this 'drain' issue could be totally coincidental & separate, it is hard to ignore the impact of the A/C damage to the overall situation, until such time as we can separate & compartmentalize the issues better. It is very hard right now because we haven't gotten there yet. But separating & isolating anything related to the A/C is a first good step. I wish I could help with identifying the location of the Dometic RVC Interface & associated wiring but my system is configured differently. If it wasn't for the fact that the CZONE is on the same Ckt. #8, it would've been easy to just pull Fuse 8 (7.5A).

Remember this Ckt. #8 and anything connected to it is still highly suspect - why? Because you had already blown this 7.5A fuse during the accident. As I previously mentioned on that previous thread - "It may slip the cursory check and could bite you later". As much as I wish it wasn't, this could be the "bite you later" issue I was afraid of.

Going back to the "Recovering from deep discharge" concern - if I was in this situation, I would totally 'Disconnect' & 'Isolate' my batteries - i.e. using the door switch & big red switch & disconnecting the main cables (red & black) going to the batteries. But that is a big ask to do on the road, even if you had easy access to the battery cables. So maybe at a minimum, disconnect via the disconnect switch near the door. You can still charge the batteries via shore, gen, solar or the Sprinter charging system BUT totally isolated from any suspect loads. Ideally, when I am trying to test batteries, I want to do so on the bench instead of in the vehicle, so any bench testing may have to wait until you get home.

This is a tough call because you need to decide which is the worst of the 2 evils - can you do the rest of the trip without using your batteries or how much longer can your batteries sustain this fast rate of discharge without possibly damaging them permanently? Hopefully, if it's not discharging too low, it's still ok.
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Old 10-22-2021, 05:55 AM   #9
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An update: as an experiment and to further diagnose, I pulled the fuse on the AC/C-Zone circuit. I did it while we hiked Old Rag in VA yesterday (great hike!) where we had great sun exposure in the van, and I did it overnight last night after we got all of the systems tidied up (as we obviously can’t control water pump etc. once the C-Zone is out).

In both cases the battery stayed at what I would consider “normal” levels based on my prior experience. Voltage was reading 12.1 when we left for the hike, and was in the 11.9 to 12.0 range when we returned just under 5 hours later.

So while the batteries might still need some love after the stress they are going through, I think the culprit lives somewhere on that circuit. I’ll prioritize getting on the roof and investigating the AC side of things once I land in FL. For now I think I can manage the batteries by disabling that circuit opportunistically.
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Old 10-22-2021, 06:07 AM   #10
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Yeeaaayyy!!!

Good job problem-solving, and thanks for keeping this updated.

Maggie
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Old 10-22-2021, 06:31 AM   #11
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Not at all an expert on these things, but perhaps it's the C-Zone system itself trying to communicate.

You pulled the plug on the C-Zone circuit and things are okay. My understanding is the a/c is still not in place. Is there any chance that the C-Zone system is spending lots of electrons trying to get the missing a/c unit to do something? Or perhaps it's just spinning and spinning looking for the a/c unit?

What makes me think of this is how my smartphone can suddenly run through a battery doing nothing much at all if we're in an area with a bad network - it will continually try to make a connection and doesn't rest till it does. You've got a complex system, and perhaps it's trying to do the same and continually is trying to make a connection to the a/c unit.

Is there a way you can tell the control panel that you don't have an a/c system?
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Old 10-22-2021, 10:33 AM   #12
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You pulled the plug on the C-Zone circuit and things are okay. My understanding is the a/c is still not in place. Is there any chance that the C-Zone system is spending lots of electrons trying to get the missing a/c unit to do something? Or perhaps it's just spinning and spinning looking for the a/c unit?

What makes me think of this is how my smartphone can suddenly run through a battery doing nothing much at all if we're in an area with a bad network - it will continually try to make a connection and doesn't rest till it does. You've got a complex system, and perhaps it's trying to do the same and continually is trying to make a connection to the a/c unit.

Is there a way you can tell the control panel that you don't have an a/c system?
It's exactly what it's doing. It's 'polling' for the A/C either because of a short or wire disconnected. The actual part that does that is the Dometic RVC Interface I mentioned in my prior post. That is the part that connects to the CZONE on one end and connects to the RV Can Bus on the other end. It could be stuck in 'polling' mode with the Can Bus and as you said, just spinning forever trying to connect or communicate with A/C.

The way to "tell the control panel that you don't have an a/c system?" is to totally disconnect the Dometic RVC Interface. But I don't know how easy it would be to access this on his AI19. Removing the fuse is at least a good temporary workaround to protect his batts from undue hi-discharge stress for now.
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Old 10-23-2021, 01:01 AM   #13
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I pulled the fuse on the AC/C-Zone circuit.

For now I think I can manage the batteries by disabling that circuit opportunistically.
CAVEMANB - I forgot to say - if you want to make your temporary workaround a little easier, get one of these ATC Bypass switch assemblies. The fuse stays in the bypass contraption and all you need to do is turn it ON/OFF whenever you need to. Auto parts stores (may be hit/miss) but Amazon should have them or
e-Trailer.

Good job troubleshooting on the road. It still sucks but now I think you're slowly getting things isolated to a manageable block.

Good luck on the trip.
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Old 10-24-2021, 06:47 AM   #14
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I’m going to get one of those switches ASAP. Thanks for the tip.

I too shave wondered about the polling. I’m going to research a bit more, but I suspect that because it relies so much on auto discovery of devices on the bus that there may not be an easy way to resolve. But a good thread to pursue.
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Old 10-24-2021, 08:55 AM   #15
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Hi

If you are depending on voltage to work out your battery state, there are a lot of issues with that. One is temperature. As the batteries get colder, the "magic voltages" move up. Given the location of the batteries under the van, it may not be easy to guess what temperature they really are at. If they are down around freezing, the voltages may move up by as much as a half volt.

What this means is that 11.9V might be the same state as 11.4V at "normal temperature". You would be way past the "stop using" point. Charge wise, you need to get to higher voltages to complete the charge cycle. All this is on top of the capacity of the batteries going way down when they are cold.

Lots of variables ....

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Old 10-25-2021, 05:21 AM   #16
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If you are depending on voltage to work out your battery state, there are a lot of issues with that.

Bob

Totally agree and understand Bob. Honestly I don't think there's any chance things are better than the monitoring is telling me, and I also know we aren't doing the batteries any favors with our current operating mode. Fortunately we are in the south, gradually working our way towards a "parking" situation in FL where I'll be able to get on the roof, work with my nephew (car expert) on re-charging, etc. We've had to adapt our plans a bit to do less boondocking and more campground camping. Tonight we were in a hotel .


Fortunately even with our Harvest Host spots, we've been isolated and able to run the generator at times to keep things minimally functional.


I truly appreciate all the input and guidance I'm receiving here. Y'all have proven again and again the power of the hive mind.
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Old 10-26-2021, 05:50 AM   #17
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Try this

This is worth a shot. Worked for me. The 2019+ chassis also has fuses under the PASSENGER feet well. Not under the seat. Under the feet. Found a blown fuse and it started charging properly while driving again. Can't remember the fuse number. But easy to check with volt meter, without taking out the fuses. Worth a shot!
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