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Old 02-20-2016, 01:22 PM   #1
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2004 22' Interstate
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House battery not charging from alternator

re: 2004 interstate sprinter motorhome (freightliner, 2500)

Hi folks, I'm a complete nube, have been lurking for a couple months as I'm the proud new mama of a nearly vintage 2004 freightliner sprinter interstate, twinsie ("Naner"), as of December. Having a real hard time keeping her house battery (located under the passenger lounge) happy. I have read most if not all of the battery threads, my interstate manual, my sprinter manual, and lots of random stuff on the web but can't find a straightforward answer to my very simple question, so now I'm hoping one of you wise folks can help.

Here it goes: should my under-the-lounge coach / house battery (was a brand spankin new AGM two months ago...now hopelessly gone over to the other side, I'm told) be charging off my alternator while driving? Is there a built in BIM / relay / isolator on my particular model? The coach battery is definitely not recharging for me while driving, only house power or the genny work to bring it back up. Took a while to determine that, but I'm sure of it now. Trying to determine if I should be troubleshooting or simply looking to invest in a smart battery relay, something like this one:

Blue Sea Systems SI-ACR Automatc Charging Relay - 12/24V DC / 120A https://www.amazon.com/dp/B000OTIPDQ..._-WjYwbYQSPGBE

The gory details: I'm new to this entire universe, but since taking delivery on "Naner" in December, I've discovered that boondocking / dry camping is my life's passion. I live in the SF Bay Area where the possibilities are endless, but stealth mode is a necessity (aka genny not always the best idea) and outlets not always (ethically) available. Long term I really want to go solar, but that's an entirely different convo....

Anyway, let's just say me and Naner are still getting to know each other, which is a nice way of saying that for one reason or another over the course of several long weekends and due to my complete ignorance I've managed to completely destroy a brand new AGM aux battery by running it down, into the ground, like 5-6 times, to the point where it wouldn't even hold enough charge to let me use the battery disconnect.

Ok so now I know that I absolutely can't let that happen anymore, as yesterday I had it replaced with a brand spankin' new ASM battery--same specs, to the tune of about $200. What I learnt in that process is that maintenance is key if I'm gonna stick with the AGM rather than going deep cycle...again, an entirely separate discussion that I'm not ready to have considering my sunk cost. Btw I also ordered a noco genius (charger / maintainer) to help with battery maintenance, but again that will really only help me between trips. I drive a lot and move a lot (never in one spot two nights), so I'm convinced that leveraging the alternator to keep my ASM topped off will make life sooooo much easier. So should I be looking for a shredded "y" cable or shopping for widgets like the Blue Sea charging relay?

Thank you so much for any insights you have!!!

~Angela
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Old 02-20-2016, 04:24 PM   #2
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Hi, Angela, and welcome to Air Forums! And welcome to T1N Sprinter ("Freightliner") ownership in particular!

My response to your question is that I could never get the danged alternator to charge the house battery to my satisfaction. The performance seemed to be variable, and my husband thought that it might have had something to do with the overall demands on the system. Such as, if it was hot outside and I happened to be running the Sprinter air conditioner (not the roof A/C), sometimes the house battery charge would only replenish by 5% per engine-running hour (we installed a TriMetric monitor which is more precise than the Airstream-installed monitoring device, so we could see percentages). And I'm referring to a low-charged battery, not one trickling near the top of charge (which would not be expected to top off as quickly). OK, that's just plain impractical - that means I'd have to drive for 5 hours just to make up the battery depletion associated with one night of light-duty boondocking.

Other times, the "percent full" would seem to rise more rapidly while I was driving. I just did not get any sense of a pattern or what to expect.

We did not pursue the reasons why this variability might be occurring. There are things that can be done to increase alternator charging capacity, but they aren't easy or cheap, and there are other ways to accomplish the same goal. We decided instead to DIY a solar system rather than mess with the alternator. If you've been reading these threads, you might have come across the blog post trilogy I did on this subject, which is here:

http://www.interstateblog.blogspot.c...ch/label/SOLAR
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Old 02-21-2016, 12:04 AM   #3
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Angela,

While I am familiar with how the battery works in a 2011 and newer models, I could find very little about how Airstream hooked it all up in 2004. I did find a manual for that year, and no mention is made of charging while driving down the road-they may not have provided for it at all. If you are new to the Interstate, I have to ask what is drawing power while you drive? There should not be much. If there is a battery disconnect, then by all means, disconnect it while driving.

I found one post that said no charging while driving was caused by a bad relay under the seat and the charger never will fully charge the batteries as they expected it to be connected to shore power every night! And in 2004, that may have been true. It's hard to diagnose a 2004 because of the inability to figure out how they wired it and what they used.

You should take it to someone who knows RV's and let them take a look. Good luck.
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Old 02-21-2016, 06:13 AM   #4
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Go to the sprinter forums.
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Old 02-21-2016, 08:09 AM   #5
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Quote:
Originally Posted by gmillerok1 View Post
.... If there is a battery disconnect, then by all means, disconnect it while driving.
....
If it's set up the way the later T1N Interstates are, the house battery won't charge while driving unless it is on.

Looking on the internet, the 2004 owner's manual (PDF link) is actually more detailed and specific than our 2007 manual, which is rather generic. I downloaded a copy of the 2004 just to have it in case there is info in there that we could use. Not to say the two years would be identical, but it could be useful.

There may be parasitic loads on the system and there have been threads about that topic, but I suspect the OP's core issue is that the alternator was simply never designed to do the recharging job under most boondocking conditions. Constant long-distance travel conditions, maybe. But not local travel with boondocking (e.g., arrive at a specific national park or forest and move from place to place over successive days). Until our solar was installed, I simply defaulted to this procedure:

-- boondock for a night
-- hookup for a night
-- boondock for a night
-- hookup for a night
-- rinse, repeat

My husband thought that perhaps we could squeeze two successive boondocking nights out of the battery, but we never tried it. In my experience, 24 hours off-grid resulted in a 25% house battery drop. So, if it followed suit, the second 24 hours off grid would produce another 25% drop, but that's putting the battery right at the cusp of permanent damage, so why risk it?

And what if, for whatever reason of nonlinear draw, it was more than 25% on the second night? Then it would certainly be damaged. Not worth the experiment.

Bottom line is that the T1N Interstates were no more designed for perpetual boondocking than the newer Interstates are. The situation requires either constant infusions of shore power or the running of the generator or long-distance engine running or solar. Those are the four options that we have to date (excluding lithium from the discussion for the time being).
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Old 02-21-2016, 12:30 PM   #6
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I have a 2006 T1N with a single 12 volt marine/rv wet cell battery and a 100 watt Renology solar suitcase. We have lasted 4 nights boondocing with this setup. I have changed out all our bulbs to led's and I reposition the solar suitcase for optimal performance. My house battery definitely charges from the alternator while under way but I like a good 120v hook up for a full charge at least every 5th day. Interestingly my house battery charges from the alternator even when the house battery switch is in the off position. From the comments i read here and elsewhere I'm beginning to believe no two Airstream Interstates are wired the same even when they are the same vintage
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Old 02-23-2016, 08:09 AM   #7
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Originally Posted by Sebtown View Post
... From the comments i read here and elsewhere I'm beginning to believe no two Airstream Interstates are wired the same even when they are the same vintage
If you take the sum total of what's been said on multiple threads by multiple users, the preponderance of statements seems to support that suggestion. If we had access to more schematic information, we would be in a better position to confirm or deny the existence of variability.
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Old 02-23-2016, 08:23 AM   #8
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Quote:
Originally Posted by InterBlog View Post
If you take the sum total of what's been said on multiple threads by multiple users, the preponderance of statements seems to support that suggestion. If we had access to more schematic information, we would be in a better position to confirm or deny the existence of variability.
That presumes Interstates are wired according to a schematic…
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Old 02-23-2016, 02:54 PM   #9
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Quote:
Originally Posted by Protagonist View Post
That presumes Interstates are wired according to a schematic…

How true! I got schematics for mine and it's not wired exactly the same as the schematic drawing. Mostly accurate, but a few minor differences.


- - Mike
2013 Interstate Lounge EXT on 2012 Sprinter
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Old 02-23-2016, 04:09 PM   #10
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Originally Posted by Boxster1971 View Post
How true! I got schematics for mine and it's not wired exactly the same as the schematic drawing. Mostly accurate, but a few minor differences.

- - Mike
2013 Interstate Lounge EXT on 2012 Sprinter
Can you remind us again how you managed that feat? Husband and I could really use the 2007 version right about now. I've been thinking about opening a dialog with Jackson Center. The T1N's are now 10+ years old... not exactly cutting edge competitive advantage they are protecting by withholding the drawings. I remember this general topic being discussed on a thread about a year ago but I do not recall the bottom line(s).
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Old 02-23-2016, 06:21 PM   #11
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Quote:
Originally Posted by Sebtown View Post
I have a 2006 T1N with a single 12 volt marine/rv wet cell battery and a 100 watt Renology solar suitcase. We have lasted 4 nights boondocing with this setup. I have changed out all our bulbs to led's and I reposition the solar suitcase for optimal performance. My house battery definitely charges from the alternator while under way but I like a good 120v hook up for a full charge at least every 5th day. Interestingly my house battery charges from the alternator even when the house battery switch is in the off position. From the comments i read here and elsewhere I'm beginning to believe no two Airstream Interstates are wired the same even when they are the same vintage
Don't the T1Ns usually have their battery located under the passenger seat? At least all of the older Interstates that I have worked on have had them in that location.

If so, that IS NO PLACE for a wet cell battery that will regularly out-gas as it charges, unless you have made some other arrangement for the dispersion of the gassing.

Just a thought………..
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Old 02-24-2016, 04:42 AM   #12
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Don't the T1Ns usually have their battery located under the passenger seat? At least all of the older Interstates that I have worked on have had them in that location.

If so, that IS NO PLACE for a wet cell battery that will regularly out-gas as it charges, unless you have made some other arrangement for the dispersion of the gassing.

Just a thought………..
It depends on the layout but many of them do, yes. Ours does. I think the ones that have the spare tire mounted on the rear door do not, but they seem to have been produced in low numbers. In those versions, it's under the rear couch.
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Old 02-24-2016, 06:19 PM   #13
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I'm still learning about our electrical system but most alternators put out 13.8-14.0 volts which is above the float maintenance voltage of 13.3 but well below Lifeline's recommended absorption charge voltage of 14.4. This means that charging with the alternator should be much slower than when charging off a converter/inverter.

So after I recalibrated those expectations, I learned that the battery isolation relay that separates the house battery from the chassis battery only connects the two batteries when the chassis battery is fully charged (above a preset voltage) so there will be times when the engine is on but the house battery is not connected. Additionally, if the house battery is really depleted or there is already a heavy draw on the alternator, charging the house battery could drag the chassis voltage below the preset voltage cutoff in the battery isolator, causing the house battery to disconnect.

Many of the T1N Sprinters have the battery isolator installed under the driver's seat as a Mercedes option and wiring diagrams can be found on Sprinter Forums.
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Old 02-24-2016, 07:37 PM   #14
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Quote:
Originally Posted by LB_3 View Post
I'm still learning about our electrical system but most alternators put out 13.8-14.0 volts which is above the float maintenance voltage of 13.3 but well below Lifeline's recommended absorption charge voltage of 14.4. This means that charging with the alternator should be much slower than when charging off a converter/inverter.

So after I recalibrated those expectations, I learned that the battery isolation relay that separates the house battery from the chassis battery only connects the two batteries when the chassis battery is fully charged (above a preset voltage) so there will be times when the engine is on but the house battery is not connected. Additionally, if the house battery is really depleted or there is already a heavy draw on the alternator, charging the house battery could drag the chassis voltage below the preset voltage cutoff in the battery isolator, causing the house battery to disconnect.

Many of the T1N Sprinters have the battery isolator installed under the driver's seat as a Mercedes option and wiring diagrams can be found on Sprinter Forums.
Your Sprinter alternator should have a stable output of 14.2VDC. My old T1N had this exact output, as does my newer 2011.

The older style diode-based battery isolators have a significant amount of voltage drop which might be the cause of the lower voltage that you are seeing. If so, it would be a good idea to upgrade to the newer battery isolation modules from companies like Precision Circuits or Blue Sea Systems which show little to no voltage drop across their latching solenoids.
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