Alternator Charging House Batteries

[jerhofer]

When I bought my used 2013 AI a few months ago the house batteries were way down on their charge as the unit had been sitting around a lot. Not long after purchasing it, I had the radio cut out on a short trip to downtown Charlotte. At that point I was still trying to figure out all of the systems and decided that I had not sufficiently charged the house batteries. From that point on I have always plugged in the power cord to my garage outlet.

On subsequent trips I did not have any issues with the radio. These were all trips of less than three hours in duration. However, on our recent trip to northern Indiana at Thanksgiving, the radio cut out again. This was the longest trip we had taken and we had to start the generator to charge the batteries. We were using the refrigerator, the radio and the inverter as my grandson was using his Playstation 4 to play his video games. At that point I was pretty sure the alternator was not charging the house batteries.

I called my dealer to discuss this issue and he wasn't sure the alternator charged the house batteries. Based on reading threads on this forum, I was pretty sure it did. I talked to Dan in service at Airstream who was very helpful. He confirmed that the alternator did charge the battery and explained how it worked. Once the truck battery is fully charged and, if the house battery is below a specified voltage level, the alternator will then charge the house batteries. His suggestion as possible trouble areas were the two fuses in the charging system. One was under the driver's seat and the other one was in the rear under the seat in the center area.

To access the latter area, a wooden cover must be removed. The vertical part is laminated to match the cabinets while the horizontal top that covers the wiring area is a thin piece of luan held in place by two screws. After I removed the cover and set it down, the two screws pulled through the luan. To remedy that I installed washers on the two existing screws and then added three more screws.







There are three red wires on the terminal on the side of the battery box. They all lead into the center area with one of them running to a fuse block and then to a round relay mounted on the right side.





This fuse block contains a 125 amp fuse. I attached my voltmeter leads to check each side and found 12.92 volts on the right side and 0 volts on the left side. The fuse was blown.



Dan told me I could get this fuse at any auto parts store. I tried NAPA, Advanced, Autozone, O'Reilly's and a local place to no avail. Many of them had this type of fuse but it was a larger version that would not fit this fuse block. I then went to the dealer who had never seen a fuse like it. They called Airstream and ordered three for me.

On the way back from the dealer, I stopped at a local stereo store and they had fuses that would fit. They only had 100 amp and 150 amp so I bought the 100 amp to at least get the system working while I wait for the fuses to arrive from Airstream. These fuses are called "midi" fuses and I found some 125 amp fuses on eBay.

I installed the fuse and I now had 12.92 volts on each side. I started the truck motor and waited for the relay to click announcing that the charging was in process. I waited for awhile and nothing happened. I then realized that, because I have had the AI plugged into my garage circuit, the house battery voltage level was too high for the system to initiate charging. So I turned on the furnace and was soon rewarded with the click. I now read 14.03 volts on both sides which verified that the alternator was charging the house batteries.





My last question to Dan was, if I found the fuse was blown, what was the likely culprit. He said it could be a voltage surge but more likely someone was working in that area and unknowingly shorted out the line. After confirming that everything was working correctly, I looked for areas where an accidental short could happen. One was at the fuse block where the heat shrink tubing did not completely cover the contacts. I added heat shrink to these areas.





The other obvious point was where the lead attached to the relay. It was on top and I could surely see a tool inadvertently touching it. I installed additional heat shrink tubing here as well.





Thee was one additional area where a 12 volt line attached to a terminal board. This would have required some type of cover which I may address in the future. I wasn't quite as concerned about this area as it is all the way to the rear of this area.



While the home is still under warranty, based on the dealer's lack of information about this system, I decided to fix it myself. When I ordered the fuses at the dealership, I did talk to the service desk guy and told him what I had found. He appreciated my telling him how the system worked and where I found the fuse block. In his defense, they sell many different types of motorhomes at his business with the Interstates being a small part of their overall sales. And I understand why they did not have the fuse in stock as I would think this would be a relatively rare occurrence and the fuse is obviously not a common one. As for me, I now have gained some more knowledge about how things operate and where I can find items. Besides, being retired, what else do I have to do!!

[73shark]

Good write-up. FWIW, the luan cover was a fairly recent addition due to the possibility of a seat belt falling down into that ridiculous nest of wires and shorting something out. AS initiated a recall to install the cover on previous model years. Not sure but I think they put more than three screws in mine.

I know the first time I got into that mess to check out my BIM problem, I was appalled at the lack of neatness in the wire routing. But after looking in other normally hidden areas, I found the same thing. Reinforced my theory that not only is Quality not Job 1 at Airstream, it's not even in their vocabulary.

[toskeysam]

Excellant writeup. My 2013 AI (late model year so I got the Magnum Inverter/Charger) uses 200amp fuses. I ran into the same problem getting replacement fuses. Wound up ordering on Amazom. I carry extras now. To date I have not blown a fuse, but after reading many of the articles on the forum it looked like a good idea to get spares.

[lewster]

Nice work and very complete chronicle of the project! Here is what the rat's nest that Airstream leaves under the rear lounge should look like. This is what I call a stage 1 wire clean-up. Stage 2 would involve removing most of the wiring and re-route them for completely smooth straight wire runs.....the way they should be! Stage 3 has me starting from scratch and doing it my way.

This is from a major electrical overhaul of an AI, including 300 watts of solar with full-function battery monitoring system, new 300 amp/hour Lifeline batteries, new Magnum MMS-1000 sine wave inverter/charger, cell and WiFi boosters and assorted other goodies.

The rear access door is now hinged or better access and the Magnum is attached to the door for easy, drop-down access. We disconnected the BIM since the new Lifelines DO NOT LIKE unregulated constant charging voltage of 14.2 when they should be floating at 13.2.

The newer AIs with the Precision Circuits BIM work far better and will disconnect completely when the house batteries reach full voltage after an hour....which is acceptable and will not overcharge the Lifelines.

[HowieE]

I called my dealer to discuss this issue and he wasn't sure the alternator charged the house batteries. Based on reading threads on this forum, I was pretty sure it did. I talked to Dan in service at Airstream who was very helpful. He confirmed that the alternator did charge the battery and explained how it worked. Once the truck battery is fully charged and, if the house battery is below a specified voltage level, the alternator will then charge the house batteries. His suggestion as possible trouble areas were the two fuses in the charging system. One was under the driver's seat and the other one was in the rear under the seat in the center area.

I have to ask about this statement of how the charging system works. It is my understanding that unless there is a switching device between the truck and coach batteries the alternator regulator once it senses a charged battery voltage it will shut down. I do not know of such a sensing system.

[jerhofer]

Originally Posted by lewster

Nice work and very complete chronicle of the project! Here is what the rat's nest that Airstream leaves under the rear lounge should look like. This is what I call a stage 1 wire clean-up. Stage 2 would involve removing most of the wiring and re-route them for completely smooth straight wire runs.....the way they should be! Stage 3 has me starting from scratch and doing it my way.

This is from a major electrical overhaul of an AI, including 300 watts of solar with full-function battery monitoring system, new 300 amp/hour Lifeline batteries, new Magnum MMS-1000 sine wave inverter/charger, cell and WiFi boosters and assorted other goodies.

The rear access door is now hinged or better access and the Magnum is attached to the door for easy, drop-down access. We disconnected the BIM since the new Lifelines DO NOT LIKE unregulated constant charging voltage of 14.2 when they should be floating at 13.2.

The newer AIs with the Precision Circuits BIM work far better and will disconnect completely when the house batteries reach full voltage after an hour....which is acceptable and will not overcharge the Lifelines.

It was very tempting to spruce up the wiring. When I wire cars I am very meticulous about how the wires run and trying to hide as much wiring as possible, especially in the engine bay. At least the wiring is hidden here. I am more bothered by the microphone installation for the radio as it in very visible. I intend on making that look better when I get some time.

[jerhofer]

Originally Posted by HowieE

I called my dealer to discuss this issue and he wasn't sure the alternator charged the house batteries. Based on reading threads on this forum, I was pretty sure it did. I talked to Dan in service at Airstream who was very helpful. He confirmed that the alternator did charge the battery and explained how it worked. Once the truck battery is fully charged and, if the house battery is below a specified voltage level, the alternator will then charge the house batteries. His suggestion as possible trouble areas were the two fuses in the charging system. One was under the driver's seat and the other one was in the rear under the seat in the center area.

I have to ask about this statement of how the charging system works. It is my understanding that unless there is a switching device between the truck and coach batteries the alternator regulator once it senses a charged battery voltage it will shut down. I do not know of such a sensing system.

There is some type of sensing device as there is an audible click when the alternator charging of the house batteries commences. I assume it is that round device that the wiring runs to from the fuse block.

[lewster]

In the 5th photo in the OP, on the right side wall, you will see a large solenoid and a sensing/control unit just below it. This pair is what determines when the batteries are connected/disconnected.

This is the older style unit. The newer AIs use a similar, but superior BIM from Precision Circuits Inc. It will only link both battery banks when either is being charged (from whatever source) and the other battery is below 80%.

When both banks are full, it will disconnect after one hour, and will not let one bank draw down the other.

It also has a manual over-ride that connects the 2 banks that will allow for either engine starting or generator starting if the respective bank is low.


Lew Farber
RVIA/RVDA Nationally Certified Master Tech
Master Tech Energy Systems, Inc.
AM Solar Certified Installation Center
Lifeline Batteries**Magnum Inverters
541-490-6357

[HowieE]

Thanks Lew

For years the trailer industry claimed hat both the TV and trailer could do this when in fact they could not.

An interesting idea that solved the problem for coaches but limited with trailers by not having a large enough wire to the trailer to carry full charging current.

[jerhofer]

Originally Posted by lewster

In the 5th photo in the OP, on the right side wall, you will see a large solenoid and a sensing/control unit just below it. This pair is what determines when the batteries are connected/disconnected.

This is the older style unit. The newer AIs use a similar, but superior BIM from Precision Circuits Inc. It will only link both battery banks when either is being charged (from whatever source) and the other battery is below 80%.

When both banks are full, it will disconnect after one hour, and will not let one bank draw down the other.

It also has a manual over-ride that connects the 2 banks that will allow for either engine starting or generator starting if the respective bank is low.


Lew Farber
RVIA/RVDA Nationally Certified Master Tech
Master Tech Energy Systems, Inc.
AM Solar Certified Installation Center
Lifeline Batteries**Magnum Inverters
541-490-6357

I knew someone would know the technical ins and outs.

By the way we were in Hood River during the summer of 2013. It was spectacular watching the kiteboarding and we had a couple great meals. Very nice area.

[lewster]

Originally Posted by jerhofer

I knew someone would know the technical ins and outs.

By the way we were in Hood River during the summer of 2013. It was spectacular watching the kiteboarding and we had a couple great meals. Very nice area.

You should have called.....we could have had a beer..........or something......


I'm there from May thru Sept every summer.

[wayneskid]

Originally Posted by lewster

The newer AIs with the Precision Circuits BIM work far better and will disconnect completely when the house batteries reach full voltage after an hour....which is acceptable and will not overcharge the Lifelines.

Hi Lew, AIs older than jerhofer's also had PC BIMs. My 2010 model AI has a Precision Circuits BIM (#00-10021-000) which includes a Trombetta contactor/relay (#114-1121-020). It took a lot of time, phone calls, trips to Airstream dealer(s), etc to get it sorted out but once I replaced the BIM the charging system worked fine.

[gmillerok1]

Lew,

I have a couple of questions if you don't mind. What's the thing next to the Magnum on the floor with the round knob to the right of the Mangnum you installed? Another disconnect? And where did you put the new batteries? Which models battery (6vdc or 12vdc)? Just trying to get an idea as to what's possible. Maybe I will catch you on the way back to Oregon.

To the original poster, I noticed his Interstate had the Tripplite 750watt inverter/charger. It will overcharge the batteries if left plugged in 24/7. You can come look at the big rust spot ion the floor where it boiled away the juice in my wet cell batteries in my former Roadtrek. I since replaced mine with the Magnum and even though pricey, it's definitely worth it. Now I no longer worry about it at all and keep it plugged in all the time when in storage.

Thanks,
Gerald

Originally Posted by lewster

Nice work and very complete chronicle of the project! Here is what the rat's nest that Airstream leaves under the rear lounge should look like. This is what I call a stage 1 wire clean-up. Stage 2 would involve removing most of the wiring and re-route them for completely smooth straight wire runs.....the way they should be! Stage 3 has me starting from scratch and doing it my way.

This is from a major electrical overhaul of an AI, including 300 watts of solar with full-function battery monitoring system, new 300 amp/hour Lifeline batteries, new Magnum MMS-1000 sine wave inverter/charger, cell and WiFi boosters and assorted other goodies.

The rear access door is now hinged or better access and the Magnum is attached to the door for easy, drop-down access. We disconnected the BIM since the new Lifelines DO NOT LIKE unregulated constant charging voltage of 14.2 when they should be floating at 13.2.

The newer AIs with the Precision Circuits BIM work far better and will disconnect completely when the house batteries reach full voltage after an hour....which is acceptable and will not overcharge the Lifelines.

[lewster]

Hi Gerald,

That is the disconnect switch for the DC positive to the inverter. It is downstream of the inverter fuse, which in this case is a 200 amp class T fuse.

The battery box was removed and floor filled in. The 2 300 amp/hour Lifelines are placed over the new re-inforced flooring on passenger side.


Lew Farber
RVIA/RVDA Nationally Certified Master Tech
Master Tech Energy Systems, Inc.
AM Solar Certified Installation Center
Lifeline Batteries**Magnum Inverters
541-490-6357

[MaineStreamer]

I am trying to figure out the jargon used in the above discussion. What does AI stand for? What does BIM stand for? I gather that PC stands for Precision Circuits, a company. Correct?

[Protagonist]

Originally Posted by MaineStreamer

I am trying to figure out the jargon used in the above discussion. What does AI stand for? What does BIM stand for?

AI - Airstream Interstate.

BIM - Battery Isolation Module, a relay and sensor package that measures voltage in the house and chassis electrical systems, and either connects the two for charging or isolates them to prevent a drain on one system from depleting the other as necessary.