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Old 03-01-2021, 04:34 PM   #1
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2018 Interstate Grand Tour Ext
Tuscaloosa , Alabama
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"Realistic" expectations for battery when boondocking

Hi Airstream Interstate GT owners,
I am very new to my 2018 AirstreamGT..We purchased it used and have been traveling PT since Mid-December. Most of the time we've been at locations with some hook ups etc..but recently began traveling to Ntl forest campgrounds/state campground that have no hookups.

My questions relate to battery life. Our unit has 3 solar panels..but, recently experienced a series of unfortunate events.

As in full battery discharge overnight and needing to jump start my vehicle. First time, I figured the battery was OEM (so I replaced the battery)..and the 2 house batteries were replaced by the previous owner in Aug 2020.

This past weekend, off I go camping, armed with the new AGM battery..and the same thing happened. A fully discharged vehicle battery by the morning. So, I need to do a sanity check and make sure I am not expecting too much from my airstream when off-grid vs that I have a battery problem.

So, looking for some experienced feedback.
If camping overnight, with no hook-ups, and assuming the battery read 100% (HSE 13.0/CHS13.1) at the beginning of the evening.
What are the expectations I should have?
I know it 'depends' on how much electrical draw is occurring, so from your experience what is reasonable?

What can or can not be turned on overnight?
Can we have lights on for any duration of time?
Can we have the refrigerator on or not at all?
Can we leave the water pump on?
Can we have any ancillary items on?
and the bigger question that I am still trying to wrap my mind around is, why would the vehicle battery be draining if the electrical use should be coming from the 2 house batteries and not the vehicle battery.

[[Background Note: After the first instance (before buying a new battery) I took it in to the Mercedez dealer who tested the old battery and said it was older/but tested fine (midtronics test)...(I replaced it anyway - figuring I didn't want to deal with the 3 yr old battery it the next time). They also did a quiescent current draw test with the vehicle in sleep mode. Current draw of 70amps and they said that was well within specs.]
Also - just to rule this out - we had earlier Fusion radio issues and needed to replace that = we no longer have the radio drawing from the battery without the ignition key on]]

Thank-you for your input.
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Old 03-01-2021, 06:36 PM   #2
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Your experience with the house batteries in the GT is very common. Itís possible to overnight with stock batteries, but you need to be very conscious of energy draws. There are very detailed analyses here that will help with boon docking energy conservation. First lesson I learned was that itís not possible to run both fridge and freezer overnight.

Draining of the chassis battery overnight is more concerning. That shouldnít happen. Could be a BIM issue.
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Old 03-01-2021, 06:50 PM   #3
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Schmitte, I agree. How would the chassis battery drain like that unless the BIM is letting the house batteries draw current from the chassis battery?

Our 2014.5 only has one panel but whether you have three or one, the solar can be somewhat misleading in my opinion. It only gives you a certain amount of recharge and the fridge and other draws whether you realize or not. For example, it’s easy to tell their is a draw when lights are on, but many don’t understand our radios don’t shut off and draw power even when they look off, or when the propane switch is on it has a parasitic draw on your batteries.

Have seen posts on other forums where people are struggling with their power management this winter because they don’t understand the solar output is so much less this time of year, too, because of the lower angle of the sun, but this is only part of your equation, you certainly seem to have an issue going on.

If it helps to explain what your BIM does, here’s what is written on the Precision circuits page. Your BIM should be located in the storage space under your sofa if is like ours.

From Precisioncircuitsinc.com:

(And this is about the LI-BIM (for Lithium) but same principle as yours): ...isolates the two battery systems, chassis, and coach, in a motorhome. This prevents loads in one system from discharging both. It also connects the two battery systems together during charging. Both batteries are charged if either is being charged. The coach battery is charged while driving and the chassis battery is charged while plugged into Shore Power at a campground.

Your batteries may not be able to hold as much of a charge as before by drawing them down so low, you might need to have them all checked and/or replace again, sorry to say. We learned the hard way too, but even if you were not having an issue with a component, it’s best to stay plugged in until you understand the power draws and how long you can go without causing damage to your batteries.

I think we could go about 8 hours total unplugged with lights and maybe nothing else, before our batteries went past the point of damage, if that gives you an idea of the amount of time it takes to draw down your batteries, That’s with AGM batteries. You might have a little more time but not a ton over us with more solar panels. If I remember right, damage to your batteries starts to occur when you get under 12.6 or 12.4 volts with AGMs.
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Old 03-01-2021, 08:27 PM   #4
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Got it. Thank-you for the quick reply.
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Old 03-01-2021, 08:28 PM   #5
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Thank-you for the quick response and the help...very much appreciated
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Old 03-02-2021, 05:28 AM   #6
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Quote:
Originally Posted by Vedo View Post

[[Background Note: After the first instance (before buying a new battery) I took it in to the Mercedez dealer who tested the old battery and said it was older/but tested fine (midtronics test)...(I replaced it anyway - figuring I didn't want to deal with the 3 yr old battery it the next time). They also did a quiescent current draw test with the vehicle in sleep mode. Current draw of 70amps and they said that was well within specs.]
Also - just to rule this out - we had earlier Fusion radio issues and needed to replace that = we no longer have the radio drawing from the battery without the ignition key on]]

Thank-you for your input.
They also did a quiescent current draw test with the vehicle in sleep mode. Current draw of 70amps and they said that was well within specs.]

Quiescent, I had to look it up: in a state or period of inactivity or dormancy.

This caught my eye and I think it needs clarification or expert help. A more complete definition and conditions of the test that reported a 70 Amp current draw. Is there a misplaced decimal or ?

Not an AI owner, just saw the thread and curious.

Gary
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Old 03-02-2021, 06:29 AM   #7
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Quote:
Originally Posted by Vedo View Post
....
What are the expectations I should have?
I know it 'depends' on how much electrical draw is occurring, so from your experience what is reasonable?

.....
Welcome to Air Forums, Vedo. As other posters have noted and will continue to note, your experiences are very common. Stock Interstates are not designed for boondocking. They lack sufficient electrical power, in terms of both storage and generation capacities.

Which is why so many of us have chosen to dive down a major rabbit hole of revising and hardening our electrical systems, either via DIY, or via hiring of a third party to do it for us.

My husband and I are two of the owners who chose the DIY route, and we are now essentially electricity-independent. We cannot run our roof air conditioner (the big one) for more than a couple of hours off our lithium battery, but we don't want to travel in areas and at times where the outdoor temperature is so hot that we need that a/c anyway. With the modifications we have made, we routinely travel and remain off-grid for up to 5 weeks at a time (we are both still employed, not retired, and could go much longer than that if necessary).

Here's one pic of our retrofits, just to give you an idea of how heavily one can become invested in this upfit process. Beware, in other words! We don't regret the work we've done - we think it was our best decision ever. But it took a lotta lotta time and money.

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Old 03-02-2021, 07:57 AM   #8
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Not an Interstate owner, but can you clarify?

"...They also did a quiescent current draw test with the vehicle in sleep mode. Current draw of 70amps and they said that was well within specs...."

Is that 70A per hour? If not then 70A over what period of time?

If you have a 240Ah AGM battery that can be discharged to 50% then you have about 120Ah of usable energy. So let's say overnight is ten hours. You can discharge at a rate of 12Ah.

If you are actually discharging at 70A per hour you'll exceed that limit in < 2 hours and kill your batteries in short order.

For comparison on a normal day we average ~20Ah PER DAY or ~1A PER HOUR. About 20% higher if we need to run fans or heat circulator pumps.

We have a 240Ah AGM battery that is now three years old. We easily go 4-5 days without charging.

"What can or can not be turned on overnight?"

We run our Novakool fridge full time.
We keep the inverter off (there is high phantom draw on the inverter even when not using it).
No A/C, microwave, or other 120V appliances when boondocking.
Lights are LED and we use whenever needed.
Water pump is only a big draw when pumping, which is infrequent. We leave on whenever we are in the trailer and turn off when we are away for the day.
We charge several phones, laptops, IPads, etc directly from 12V->5A USB circuits instead of using 120V->5A plugs (so we don't have to use the inverter).
We have no other "high tech" gadgets with phantom draw (TV's, DVD players, streaming devices, control panels, computer monitors, etc).
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Old 03-02-2021, 10:42 AM   #9
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Strap a Goal Zero 3000x behind the driver's seat. Run the fridge and freezer cords out of the pantry through the hole used by the TV. Start the evening with charged batteries. My 2016 Interstate can easily go overnight with minimal usage of lights and the pump, etc. I do not watch TV and will use an electric blanket instead of using propane. I don't have any issues with my starting battery. I have posted many times about this in the past, so there is a lot more detail if you are interested.
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Old 03-02-2021, 06:49 PM   #10
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Thanks all for the inputs.. basically you've all reinforced the dead chassis battery shouldn't happen.. (and I have to give a 'I don't know' answer to the question regarding 70A note from the mechanic - was just told it was within specs -- and obviously it wasn't correct- will inquire if BIM related with the next mechanic and hope to resolve it....Also, thank-you to all in reinforcing that I'm not nuts with regards to the airstream being built to live a plugged in life..or invest substantially to life off of it. All good insights, no matter how painful.
thanks again
vedo
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Old 03-02-2021, 10:12 PM   #11
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Sounds to me they could have been testing your alternator output.

I’m attaching a screen shot of the BIM in case that is your issue. Not sure if yours looks like the black version pictured, The green one is the new LI-Bim that needs to be changed out to make it work with lithium batteries. To access it, you unscrew the screws in the box behind the sofa rest area and tilt down the panel toward you. Might have to take the top off the box first. If it’s like ours, the BIM is on the right hand lower side of the box side as pictured. You can see the back side of your fuse panel on the long wall of the box. BIM has the thick red wires attached to it.
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Old 03-03-2021, 09:14 PM   #12
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A few comments. I have a 2916 chassis, 2017 house.
A) The factory solar charger is junk and must be replaced by a good model such as a Renogy Commander
B) I have found that modern computerized battery testers such as at Autozone will typically say battery is good when in fact it is not. I have proved this by replacing Ďgoodí batteries in my cars and my problems were resolved.
C) 70Amps is a ridiculous sleeping current. Perhaps he meant 70 mAmps which is 70 milli amps IE 0.070Amps. This is still a bit on the high side. I would need to measure mine. Easy to do, place your multimeter configured for amps between the ground post and the pulled connector near the gas pedal. If value is low switch to milli amps
D) with 3 AGM 80 amp batteries I can run the big fridge all night and still be above 50% charge in the morning.
E) you can observe the voltage on the house and chassis batteries on the panel behind the driver seat. They are not super accurate but will give you an idea what is happening at say midnight and 4 in the morning
F) you can tell if the BIM relay is closed (both batteries connected together) by pushing the emergency start button at the drivers left knee. If you hear the relay click then you know it was open. If you do not hear it you know it is closed.
H) the factory BIM is only somewhat smart. For example if your batteries are at 50% in the morning, no sun, you start driving, you stop after 15 min, the sun shines, you start the engine, the BIM sees high voltage because of the sun and so will not close and allow the alternator to give the batteries a good charge. Instead you may only be getting a weak charge because of weak sunshine. Point A above will exasperate the situation. This can overall lead to little charge on the batteries on a low sun day.
I hope this helps.
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Old 03-04-2021, 03:43 PM   #13
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We disconnect electrical from our tow vehicle when not traveling.
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Old 03-07-2021, 10:10 AM   #14
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Reasonable Battery Expectations

On our late-model Flying Cloud, big battery draws are NOT lights, NOT refer (running either shore power or LPG with just a dab of battery), NOT music, but could very well be the fan component of furnace. I suspect, and please correct me if Iím wrong, one of the main reasons RVers are constantly buying new batteries is too many deep draws with overnight loads like furnace fan. Lithium batteries are said to be capable of 100s if not 1000s of deep draws. Iím counting on it.
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Old 03-07-2021, 10:13 AM   #15
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Globetrotter newbie

The battery is the achilles heel of boon docking. I have only done 2 boon docking trips to National Forest campgrounds(in my new 2020 Globetrotter) and as a newbie, drained the AGM battery several times. In August with some sunshine replenishing the batteries via solar panel and not ever turning on the heat, it was a never went to zero, but did go well below 50% capacity. In September, we had overnight lows in the 30s with furnace on, the batteries went to zero within 3 hours. I recharged the batteries by running the tow vehicle and then got some recharging from the solar panels. The surrounding trees, only allowed enough sun to chart the battery to 35%. Little did I know that going to zero damages the battery and can be harmful, whenever the battery charge goes <50%. I have since replaced the battery. Next time I boondock, I will bring a generator and not let my battery capacity go below 50%, I will only briefly run the furnace(30-60 minutes) and then turn it off for the night. When these batteries need replacing in 3-4 years, I will upgrade to lithium(which according to others, has longer charge life than AGM).
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Old 03-07-2021, 12:09 PM   #16
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Nothing sucks more battery life than the heater blower. I supplement the on-board heater with an Olympian Wave heater. Had a propane line added that runs from the propane tanks into the trailer. Quick disconnect inside the trailer and quick disconnect on the Olympian heater. I too have solar. Not relying on
the on-board heater makes all the difference in battery life. Research all the threads on the safety of the Olympian. Once you start looking into this, the Mr. Buddy heater will pop up. Again research before buying.
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Old 03-07-2021, 07:55 PM   #17
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Are you running an absorption fridge on electricity? Big draw! Up to 20 amps from battery
Are you running the furnace overnight? Also a big draw, up to 10 amps when running
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