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Rapa Nui · 11-17-2014, 08:19 PM

We store our AI (2014.5) connected to shore power. Should I put a battery tender on the chassis battery? I know it's a rather basic question, but the manual isn't overly clear.

**moosetags** · 11-17-2014, 08:56 PM

If you are connected to shore power, the trailer batteries will be charged by the converter.

Brian

73shark · 11-17-2014, 09:12 PM

He has an AI. Shore power will keep both the house batteries and the starting/chassis battery charged.

UKDUDE · 11-17-2014, 09:14 PM

No need for a battery tender on the chassis battery. Your Magnum charger/inverter takes care of that through the BIM (Battery Isolation Manager), as well as the coach batteries.

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lewster · 11-17-2014, 09:21 PM

Brian, I think he was inquiring about his Interstate coach. No converter. It has a Magnum inverter/charger and an internal connection that will charge the house batteries from the alternator while the engine is running.

The larger question is: does this process work in reverse? Will the house batteries being charged by the inverter/charger apply a sustaining charge to the Sprinter engine battery?

After just completing a full solar, inverter and battery monitor package on a 2013 Interstate, we found that if you leave the headlights on, there is a significant drain (20+ amps) on the house batteries. This situation was noticed after we saw a 9 amp mystery house battery drain with all of the disconnect switches OFF. This indicates that there IS a connection between the house and engine batteries while the engine is off. If this connection exists and allows the house batteries to show a load from the chassis headlights, then it follows that the chassis battery should also benefit from the house battery charging. This would be their battery isolation manager (BIM) system in use.

I would call Airstream in Jackson Center and get their definitive answer to be certain that they have not done any upgrades/modifications to their battery charging system wiring in your new coach that would indicate this is not the case in your unit.

73shark · 11-17-2014, 11:08 PM

I do recall reading on this forum that the new ones have the capability to use the house battery to charge up the chassis battery. I think it involves changing a switch position in order to do this. Not sure how the headlights could be connected to the house batteries though. Maybe a defective BIM.

Protagonist · 11-18-2014, 06:11 AM

New Interstates have four batteries.

One Group 49 starting battery under the driver's footwell. Charged by the engine alternator, and— through the Battery Isolation Manager (BIM) and the inverter/charger— by the generator of by shore power. Not charged by the rooftop solar panel as far as I know.

One Group 49 auxiliary battery under the hood. Charged by the engine alternator only. There is a relay that disconnects the auxiliary battery from the starting battery when the engine is not running, so this battery is not charged by any of the "house" sources.

One bank of two Group 27 house batteries. Charged by the rooftop solar panel through its own charge controller, shore power through the inverter/charger, the generator through the inverter/charger, or the engine alternator through the BIM.

avanti · 11-18-2014, 06:48 AM

Just out of curiosity, what is the purpose of the Group 49 aux battery? I know that this is an option from MB, but it seems odd that AS specifies it. What does it power?

BTW: If anybody has a battery that is NOT being charged from shore power, this is easily remedied with a device called Trik-L-Start.

Ultra TRIK-L-START Starting Battery Charger/Maintainer

I recently installed one in our new GWV Legend. It's great.

Protagonist · 11-18-2014, 06:56 AM

Quote:

Originally Posted by avanti

Just out of curiosity, what is the purpose of the Group 49 aux battery? I know that this is an option from MB, but it seems odd that AS specifies it. What does it power?

It's primarily intended for ambulances, television news trucks, and other commercial users as a house battery. On the Airstream Interstates that have house batteries in the rear, it's overkill. The only things that SHOULD be hooked up to the auxiliary battery (but probably aren't) would be the sliding step, the awning, your Kenwood head unit, and the always-on 12v power outlets, in other words stuff you might use with both the engine and house system turned off. And if you install an aftermarket alarm system, that should also go to the auxiliary battery so that you can still use the battery disconnect by the accelerator pedal to disconnect the starting battery without killing power to the alarm system.

Rapa Nui · 11-18-2014, 09:27 PM

Thank you all for the insights. I'll call Jackson center to get a final word and let you know what they say. Again, thanks for you help on this. Art

Boxster1971 · 11-19-2014, 11:13 AM

Agree you will have to get answer on Auxiliary Sprinter Battery charging from Airstream. The wiring diagram that they now include with owners manual indicates the BIM, battery separator, is only tied directly to the starter battery. Screen capture of relevant part attached.

Rapa Nui · 11-20-2014, 07:26 PM

My question to Jackson Center: When my 2014.5 Interstate is hooked into shore power, are the two chassis batteries also being charged?

Their answer:

If the battery disconnect switch is in the “use” position both batteries are being charged.
Airstream Customer Relations
937-596-6111 Ext. 7401

Thank you all for your insights into this. I appreciate the Forum more than you'll ever know.
Art

lewster · 11-20-2014, 08:10 PM

Quote:

Originally Posted by Boxster1971

Agree you will have to get answer on Auxiliary Sprinter Battery charging from Airstream. The wiring diagram that they now include with owners manual indicates the BIM, battery separator, is only tied directly to the starter battery. Screen capture of relevant part attached.

Boxter,

There is a part of the schematic missing; and that is the continuation of Cable 1, which drops down the left side of the drawing from the isolator terminal marked 'coach'. What you don't see is the continuation of this cable back up to the coach battery positive connection stud.

The solenoid, when activated, will indeed connect the coach batteries with the chassis battery that is shown entering the solenoid from the right.

It would have been more helpful if they included the entire schematic and hadn't cut off the bottom!

UKDUDE · 11-21-2014, 04:45 AM

Here's a side question about battery charging, asking because I don't understand the physics involved, and maybe Lewster can explain:
If my coach batteries are down to 75% for example, and I start the generator or plug into shore power, my display usually tells me within minutes that I'm back to 100% charge. But I know that's not the case, because if I stop the generator or unplug from shore power, it will then display 80% (for example).
So with my lack of understanding of battery physics, I'm concluding there must be a superficial charge and a deep charge going on. And my question is when I have the generator charging the batteries, how do I know when they're fully charged and can turn off the generator?
Does my question make sense?

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Protagonist · 11-21-2014, 06:26 AM

Quote:

Originally Posted by UKDUDE

Here's a side question about battery charging, asking because I don't understand the physics involved, and maybe Lewster can explain:
If my coach batteries are down to 75% for example, and I start the generator or plug into shore power, my display usually tells me within minutes that I'm back to 100% charge. But I know that's not the case, because if I stop the generator or unplug from shore power, it will then display 80% (for example).
So with my lack of understanding of battery physics, I'm concluding there must be a superficial charge and a deep charge going on. And my question is when I have the generator charging the batteries, how do I know when they're fully charged and can turn off the generator?
Does my question make sense?

Your question makes good sense. And apologies to Lewster for pre-empting him.

When you have shore power or generator power as a charging source, your display shows 100% because it's reading the charging voltage, not the battery voltage. It would probably show over 100% if the display was set up to do that. Look at an actual display of volts rather than percent charge, and you'll see. Voltage is voltage, and the display can't tell the difference in where it is coming from.

I don't have a good answer for how long to leave the generator running, though. The only way I know how to tell is to shut off the generator or shore power, let the batteries sit for a while to stabilize, then read the voltage again. And if it's not enough, fire up the generator again to finish the job.

lewster · 11-21-2014, 06:53 AM

No apologies required!!!!

Your generator run time will depend on the amperage output of your charger and the state of discharge of your batteries. If you have the Magnum MMS-1012, it has a 50 amp charging section, which has an adjustable output.

The next variable is the size of your battery bank. Typically, Lifeline AGM batteries use the C/5 rule. That takes the Capacity of your batteries and divides by 5.

If you have the standard 180 hour Lifeline bank, then your preferred charger output is 180/5 or 36 amps. The closest you can set the Magnum is 40 amps or an 80% charge rate.

Next, determine your state of charge level. This is easily done by reading the resting voltage of your batteries. Let's say that they read 12.2 VDC, which is 50% for Lifelines, so at that level you will need to replace 80 amp/ hours into your batteries. At the charge rate of 40 amps from above, you would need to run the generator about 2 hours to fully re-charge your batteries.

Exceeding the run time is no problem as the Magnum will go to a 13.2 VDC float charge when they are full. It is far worse to undercharge them by not completing the charge cycle.

Questions?

Class dismissed! :-))

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

UKDUDE · 11-21-2014, 07:46 AM

Thank you Lewster and Protag, very helpful answers. And yes, I have the standard Lifelines with the Magnum.
Here in the Southwest we mainly dry camp, so generally have to run the generator morning and evening, and the question of how long has been bugging me for a while.
Peter

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Protagonist · 11-21-2014, 07:56 AM

Quote:

Originally Posted by UKDUDE

Thank you Lewster and Protag, very helpful answers. And yes, I have the standard Lifelines with the Magnum.
Here in the Southwest we mainly dry camp, so generally have to run the generator morning and evening, and the question of how long has been bugging me for a while.

By the way, for planning purposes, a full tank of propane in your Interstate will run the generator about 24 hours at half load. At full load that goes down to about 16 or 18 hours. That's if you're not using propane in the water heater or stove.

And when you're running the generator, try to load it up to somewhere between 50% and 75% of rated load. It's most efficient that way. Propane is a bit more forgiving than diesel in that regard; you're not likely to get "wet-stacking" if you under-load it. But in terms of maximum electricity for minimum propane, somewhere between 50% and 75% of the rated load of 2.5kW is best. Or since you aren't really set up to show kW of generator output, figure a load of 10- to 15-amps out of the 20 amps that the generator produces.

lewster · 11-21-2014, 07:58 AM

Quote:

Originally Posted by UKDUDE

Thank you Lewster and Protag, very helpful answers. And yes, I have the standard Lifelines with the Magnum.
Here in the Southwest we mainly dry camp, so generally have to run the generator morning and evening, and the question of how long has been bugging me for a while.
Peter

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Maybe there should be 200-300 watts of solar in your future

Boxster1971 · 11-21-2014, 08:38 AM

Quote:

Originally Posted by lewster

Boxter,

There is a part of the schematic missing; and that is the continuation of Cable 1, which drops down the left side of the drawing from the isolator terminal marked 'coach'. What you don't see is the continuation of this cable back up to the coach battery positive connection stud.

The solenoid, when activated, will indeed connect the coach batteries with the chassis battery that is shown entering the solenoid from the right.

It would have been more helpful if they included the entire schematic and hadn't cut off the bottom!

Didn't mean to create more confusion. I thought we had established many times on this forum that both the Airstream installed house batteries an the Mercedes installed starter battery are charged via the BIM. It just depends on the voltages and logic of the BIM.

The newer Interstates have an additional Mercedes installed Auxiliary battery under the hood in front of the driver. I thought the question now was is the Auxiliary battery charged via the BIM? Art's (Rapa Nui) answer from Airstream was yes. That answer is interesting because it means that Airstream has either added another logic circuit or they are defeating the Mercedes relay that isolates the Auxiliary battery from the starter battery when the engine is off.

- - Mike
2013 Lounge EXT on 2012 Sprinter