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Old 12-09-2023, 02:48 PM   #1
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2023 25' Flying Cloud
Anytown , California
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Newbie puzzled by battery draw while on shore power

Hi all, my first post to AirForums. New Flying Cloud FBQ owner and I'm confused by what I think is battery power being used while I'm plugged into shore power.

My trailer is plugged into 15A service. When the main battery disconnect is off and I look at my Victron Smart Shunt display I see 0 amps which I would expect to see. However, when I turn on the battery disconnect switch I see current being drawn (the Victron shunt display Current reads -2.24A). I'm new to all this but I assume that means I'm drawing current from the battery.

What I'm confused by is, if I'm plugged in to shore power, shouldn't my 12V devices all be powered by the converter and not draw power from the batteries and therefore shouldn't the shunt current still read 0 amps?

Thanks in advance
Brad
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Old 12-09-2023, 03:42 PM   #2
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Most 12V devices aren't dual mode (120V/12V) so when the are on they are drawing power from 12V "bus" Power to the bus comes from either batteries or the output of the converter. The shunt is measuring the flow: negative means battery is providing power and positive means the converter is with excess flowing to the batteries to charge them. Power is almost always flowing one way or the other.

Also, even with the use/store switch off, you should expect to see some draw due to parasitic loads - it shouldn't be 0

Since you are seeing a negative number and are plugged in, I'd say your converter isn't working. Is the breaker for the converter on? Is the GFCI for the outlet you are using tripped?
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Old 12-09-2023, 04:23 PM   #3
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Quote:
Originally Posted by jeffb831 View Post
Most 12V devices aren't dual mode (120V/12V) so when the are on they are drawing power from 12V "bus" Power to the bus comes from either batteries or the output of the converter. The shunt is measuring the flow: negative means battery is providing power and positive means the converter is with excess flowing to the batteries to charge them. Power is almost always flowing one way or the other.

Also, even with the use/store switch off, you should expect to see some draw due to parasitic loads - it shouldn't be 0

Since you are seeing a negative number and are plugged in, I'd say your converter isn't working. Is the breaker for the converter on? Is the GFCI for the outlet you are using tripped?

The breaker for the converter is on. The GFCI or the outlet is not tripped, I have a dehumidifier plugged into the 120v internal outlet so I can confirm the shore power is connected.

I poked around a bit more:

- If I turn on the disconnect switch and see the same negative current on the shunt display, I then unplug shore power that number doesn't change. Shore power plugged in or not doesn't seem to change the current number.

- Similarly, if I have the shore power on and the disconnect switch on, then turn off the converter circuit breaker, I still see the same negative current on the shunt.

Still puzzled.
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Old 12-09-2023, 04:57 PM   #4
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I'd say the converter is not working. Regular 120V power to the outlets doesn't flow through the converter.

One thing to check is to look at the converter and see if it is lit up. You should be able to look under the power distribution center (where the breakers are) and see a glow - green is AGM and blue is lithium. You may need to remove the plastic cover to center to see under it - 4 screws.

On mine, the converter had come unplugged from the back of the distribution panel - the breaker is directly connected to a plug. I had to completely remove the panel - 4 screws for the plastic cover then 4 more that attach to the wall - to plug it back in.
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Old 12-09-2023, 05:38 PM   #5
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Thanks for your help on this by the way.

Under the bed, there's a panel over the power center. I removed that and could see that the converter is plugged in and that the light is on.

Is there an easy way to verify the converter is working maybe by turning off the battery source somehow to the power center or something like that? Being new I'm a bit hesitant to start disconnecting wires etc.
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Old 12-09-2023, 05:41 PM   #6
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Unfortunately, AS doesn't include a battery disconnect switch. The only way to disconnect the batteries from the factory is to remove the negative leads from the batteries.
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Old 12-09-2023, 05:53 PM   #7
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One more idea, what if I pull the 30A fuse in the battery compartment?

If the converter is powered and working, would my 12v system still work with the battery fuse pulled?

If so, is there anything I should be cautious of before pulling that fuse?

Thanks very much again
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Old 12-09-2023, 06:54 PM   #8
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Not an expert here. But, if you turn your battery disconnect on, is it impossible for your converter to charge them since they are isolated from the RV?

When you say you turn on your battery disconnect, is that the use / store switch? If so, maybe the converter canít charge the batteries and the parasitic draws (CO2 detector, etc) are drawing down your batteries.

The converter could still power your 12V if you were using them but the converter would not be charging your batteries.

If you have a true battery disconnect on your batteries, vs the use / store switch as your disconnect,
them I donít know the answer.
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Old 12-09-2023, 08:26 PM   #9
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Some more information but I'm not sure what to make of it.

I still had the trailer plugged into 15A shore power. I turned on the battery disconnect switch (the store/use switch) and watched the Victron shunt current display. It went negative as stated before, when I turned on more appliances (fridge, radio, lights) it went more negative which seems at least consistent.

Now the interesting thing is that after a couple of minutes the current on the shunt display went very positive to over +12A and then rapidly declined and then dropped back to where it was before the spike. During the spike I could clearly hear the fan on the converter running. When the current dropped back down the fan also stopped running. A few minutes later the whole cycle happened again. I've attached the Victron display
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Old 12-10-2023, 08:08 AM   #10
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I think this post will hopefully answer most of your questions. The consensus from this post is that the use/store switch is not a true battery disconnect. Prior airstream converters were not 3 or 4 stage chargers and they would overcharge or boil the batteries and ruin them. Putting it in the store position would keep the converter from charging the batteries and ruining them. However, parasitic draws (see post 8 and 9) from various items would draw the batteries down. The converter can also allow you to be plugged into shore power and have the converter provide DC power to your RV. So, you can switch on your lights (12V) but the converter will not be charging your batteries. However, you said your RV will not allow this. So, either yours will not allow this (as you state) or, something was wired wrong by Airstream. Your owners manual should spell this out, as others have noted.

https://www.airforums.com/forums/f37...ry-210325.html

either way, just know that you do not have a true battery disconnect that isolates the batteries from the RV as the use/store switch is not a battery disconnect. This is a very confusing label by Airstream for any owner initially. I would suggest you keep it in the use position and plug up your Airstream to your shore power at home to get your batteries up to charge before they are completely drained by parasitic loads. Then, figure out how to maintain them when not in use.

I have solar and would just keep it in use mode and let solar keep my lead acid batteries charged in between trips. A true battery disconnect switch would work as would removing the batteries and keeping them on a trickle charger or, placing the switch in store and hooking up a battery tender straight to the batteries. If you remove the batteries, take a picture of the connections before you do. Disconnect negative first, then positive and protect all connections so they don't touch each other as it is a dangerous situation. If you have solar, make sure it is also turned off before this.

I'm sure I missed something and hopefully someone will correct me. Batteries can be dangerous so be careful.
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Old 12-10-2023, 08:53 AM   #11
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Quote:
Originally Posted by bmccarty View Post
I still had the trailer plugged into 15A shore power. I turned on the battery disconnect switch (the store/use switch) and watched the Victron shunt current display. It went negative as stated before, when I turned on more appliances (fridge, radio, lights) it went more negative which seems at least consistent.

Now the interesting thing is that after a couple of minutes the current on the shunt display went very positive to over +12A and then rapidly declined and then dropped back to where it was before the spike. During the spike I could clearly hear the fan on the converter running. When the current dropped back down the fan also stopped running. A few minutes later the whole cycle happened again. I've attached the Victron display
I think answers to these questions could help others to help you diagnose this (sorry if I missed them above...):
  1. This is a 2023 trailer right?
  2. Is this the stock WFCO converter and wiring, or has the system been modified?
  3. Do you have solar, and is it active during these tests?
  4. What battery type do you have? (flooded, AGM, lithium)
  5. What is the state of charge of the batteries reported by your shunt?
If your batteries are run down a bit (e.g. 50% SOC), you should see strong charge current from the converter, potentially up to 50A depending on chemistry, wiring, and other loads. As the batteries approach 100% SOC, the charge current should taper as the converter goes into constant voltage modes (absorption then float).

For the "cycling" behavior you're seeing, it would also be nice to see a voltage chart along with the current chart you posted from your shunt. Have you noticed that those cycles are associated with the cycling of any other loads (like refrigerator, furnace, water heater, etc.) or solar activity? Looking at your chart, it appears that two of the current spikes are immediately after apparent load increases of ~3-4A. I'm no converter expert, but it seems a bit unusual to me. Almost like it's ping-ponging between absorption and float modes--it spikes, then tapers, then drops.
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Old 12-10-2023, 09:58 AM   #12
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My guess is that you have lithium batteries and your converter thinks you have lead acid. With that your voltage is high enough that the converter doesn't start providing power until the load increases enough to lower voltage to the point that lead acid batteries would need power.
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Old 12-10-2023, 12:40 PM   #13
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Quote:
Originally Posted by DarthBrader View Post
I think answers to these questions could help others to help you diagnose this (sorry if I missed them above...):
  1. This is a 2023 trailer right?
  2. Is this the stock WFCO converter and wiring, or has the system been modified?
  3. Do you have solar, and is it active during these tests?
  4. What battery type do you have? (flooded, AGM, lithium)
  5. What is the state of charge of the batteries reported by your shunt?
If your batteries are run down a bit (e.g. 50% SOC), you should see strong charge current from the converter, potentially up to 50A depending on chemistry, wiring, and other loads. As the batteries approach 100% SOC, the charge current should taper as the converter goes into constant voltage modes (absorption then float).

For the "cycling" behavior you're seeing, it would also be nice to see a voltage chart along with the current chart you posted from your shunt. Have you noticed that those cycles are associated with the cycling of any other loads (like refrigerator, furnace, water heater, etc.) or solar activity? Looking at your chart, it appears that two of the current spikes are immediately after apparent load increases of ~3-4A. I'm no converter expert, but it seems a bit unusual to me. Almost like it's ping-ponging between absorption and float modes--it spikes, then tapers, then drops.


I REALLY appreciate everyone's help on this, please bear with me there's a lot of new terminology and a lot I still need to learn.

To answer your questions:

1) Yes, it is a 2023 25' Flying Cloud FBQ
2) It is the stock WFCO converter. As to the wiring, the dealer did the full solar installation, there was no solar from the factory. So I don't know if that installation is relevant to your wiring question.
3) Yes, solar. For the chart I posted earlier, it was dark so I assume the solar wasn't active.
4) I have BattleBorn Lithium batteries BUT, when I looked again at the converter led light color is is definitely showing GREEN no BLUE. So I guess the converter hasn't yet auto detected my lithium. (I've seen the many posts about how to try and get that fixed)
5) I didn't capture the SOC but I can try this all again tonight when it's dark.

For the voltages, I did another test early today, not sure if it was light enough for the solar to be kicking in or not, but I captured some voltage numbers. The Victron displays are attached.

While I understand that I may have an new issue with the converter thinking I have AGM batteries, my original question is still really about trying to understand the role of the converter for powering my 12V system more than for how it's charging the batteries. Simply put, should my converter ALONE be powering my 12V circuits when plugged in to shore power? Or does it work in conjunction with my batteries even when on shore power?

Anyway, hope that's clear and thanks again
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Old 12-10-2023, 12:45 PM   #14
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Originally Posted by Wazbro View Post
My guess is that you have lithium batteries and your converter thinks you have lead acid. With that your voltage is high enough that the converter doesn't start providing power until the load increases enough to lower voltage to the point that lead acid batteries would need power.
I believe you're right regarding the converter, I do have lithium batteries but today I noticed the LED on the converter is green and not blue.

I want to better understand the 2nd part of what you said about the converter starting to provide power. I have the (maybe mistaken) understanding that the converter is always providing power to the 12v circuits, is that not true? Is the normal operation of the converter to intermittently provide power depending on the load and battery voltage?
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Old 12-10-2023, 04:22 PM   #15
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Quote:
Originally Posted by bmccarty View Post
I believe you're right regarding the converter, I do have lithium batteries but today I noticed the LED on the converter is green and not blue.

I want to better understand the 2nd part of what you said about the converter starting to provide power. I have the (maybe mistaken) understanding that the converter is always providing power to the 12v circuits, is that not true? Is the normal operation of the converter to intermittently provide power depending on the load and battery voltage?
The converter should be providing power while on shore power. I believe that the float voltage for AGM is about the same as the resting voltage of your lithium batteries so the converter doesn't provide power until the voltage gets below the float voltage. If you actually had AGM batteries their resting voltage (which means not on charge and not being discharged) would be 12.8 volts or less so the converter would start providing power sooner.
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Old 12-10-2023, 07:21 PM   #16
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Now that the sun is down, I ran another test.

1) Solar is off (per Victron display)
2) Shore power is plugged in 15A service.
3) I have the store/use switch in the use mode (otherwise none of my 12v accessories work).
4) I turned on only TV (12v TV), cabin lights, radio to generate load.

What I see on the Shunt display (attached) is that the current goes to about -3.5A

The voltage drops slowly until it reaches 13.73 then it spikes and rises to 14.31V then drops off again. The current goes from the -3.5A to +14.6A and then drops off as the voltage rises to 14.31V. While this spike is happening I hear the converter fan running.

This pattern reoccurs every few minutes. Also during that time the SOC is a constant 100%.

So after everything I've read I *think* this is the normal pattern when running my 12V accessories while on shore power. I.e. battery voltage drops till 13.73, converter kicks on until voltage reaches 14.31V then stops and repeats as long as that load is constant.

Could someone verify whether or not my thinking is correct? If it's not, could I see an example of a Victron display of the smart shunt that shows what the correct graph should look like when on shore power?

Thank you all for your help so far, very much appreciated.
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Old 12-10-2023, 08:27 PM   #17
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One other test to do would be to unplug from the shore power and let the batteries run down to 80% - 85% and then plug in and see if it charges correctly.
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Old 12-10-2023, 08:58 PM   #18
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Originally Posted by jeffb831 View Post
One other test to do would be to unplug from the shore power and let the batteries run down to 80% - 85% and then plug in and see if it charges correctly.
By correctly I *think* you mean, does it charge my lithium batteries as lithium should be charged instead of how AGM batteries should be charged (i.e. to the optimal voltages and currents etc). Or do you mean something else by "correctly"?

I started to do the process to get the green light on the converter to turn blue but then I saw this video in another thread and it seemed to make sense to me, basically saying even if the auto-detect is incorrect that it will still charge my lithium batteries, even if not optimally. So I think I'm ok with that as long as it charges them. I also have solar which I think helps compensate if the converter is not super optimal. I may be wrong but for now the efficiency of how it charges the battery isn't my primary concern, that could easily change in the future.
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Old 12-10-2023, 09:20 PM   #19
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Originally Posted by bmccarty View Post
By correctly I *think* you mean, does it charge my lithium batteries as lithium should be charged instead of how AGM batteries should be charged (i.e. to the optimal voltages and currents etc). Or do you mean something else by "correctly"?

I started to do the process to get the green light on the converter to turn blue but then I saw this video in another thread and it seemed to make sense to me, basically saying even if the auto-detect is incorrect that it will still charge my lithium batteries, even if not optimally. So I think I'm ok with that as long as it charges them. I also have solar which I think helps compensate if the converter is not super optimal. I may be wrong but for now the efficiency of how it charges the battery isn't my primary concern, that could easily change in the future.
From what others have said if not set for lithium the batteries will only charge to 70-80%. Also the shunt needs to be reset to 100% when the batteries are fully charged to be accurate for charge percentage. Other then that solar should get them charged.
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Old 12-10-2023, 10:43 PM   #20
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On my trailer a current draw of only 2.24A will not always trigger the converter to start charging the batteries if they are or have recently been fully charged. It will hang out like that for a while until the cumulative draw is larger and then start charging.

When this is happening if I turn on a few other lights or 12v devices the converter will snap into action and the monitor will show a charge.

Turn on some other 12v devices and see if the converter kicks in. If it does, as long as the batteries are being charged in the long run don't stress over short-term negative indications on the monitor if they are small like this.
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