Why Interstate Lifeline AGM batteries die

[Boxster1971]

In this post I hope to give fellow Interstate owners some idea why their batteries are slowly destroyed by the Airstream installed systems and how to minimize the damage.

Some background: Since I upgraded my solar and batteries I’ve been monitoring the Battery Isolation Manager (BIM) while parked and driving. I added an indicator light so I can tell when the relay is closed connecting the starter and house batteries. I did this because it appeared to me that the BIM was connecting the batteries at less desirable times when parked and not connecting them enough when driving. I’m using the technical data on voltages from the Precision Circuits Inc. BIM, Atkinson PVCM-20 solar controller, Lifeline Technical Manual and the Magnum MMS1012 Inverter/Charger. I’m attaching copies of the technical data I used for reference. So if you have other equipment this analysis might not apply.

What I have observed is the BIM often connects the batteries when the sun is shining and you are parked. This happens because the BIM sees a charging voltage of more than 13.2V from solar on the house batteries and will connect to starter battery if it drops below 12.6V. The PVCM-20 is ON @ 12.4VDC and OFF @ 13.9VDC. This just takes some of the solar power you would like to get into your house batteries and sends it to the starter battery when it may not really be needed.

Conversely when driving in daylight the BIM will not connect the batteries even when discharged by 20-30% because it sees the voltage from the solar controller and thinks the batteries don’t need the extra charge. But then they are only getting a little trickle for your 50 or 100 watt solar panel.

These issues are compounded by the solar charge indicator inside the van that gives you a false sense that the batteries are OK. Why is this? Because the Atkinson Photovoltaic Display Module (PVDM) gives you State of Charge (SoC) based on voltages that are not accurate for Lifeline AGM batteries installed by Airstream.

These are the PVDM Battery Percent indicated voltages:
100% - 12.8V or more
90% - 12.6V
80% - 12.4V
70% - 12.2V
60% - 12.0V
50% - 11.8V
40% - 11.6V
30% - 11.4V
20% - 11.2V
10% - 11.0V
0% - 10.8V or less

These are the voltages from the Lifeline technical manual:
100% - 12.8V or more
75% - 12.5V
50% - 12.2V
25% - 11.9V
0% - 11.6V or less

Notice that when the PVDM says your batteries are at 50%, they are really less than 25%. Not good! I realize that this type of voltage readings are only accurate for a battery at rest disconnected, but they give you a sense of the difference that does not help you properly monitor your battery condition.

What can you do to counter these issues? The best thing is make sure you get plugged into external 120VAC power every few days to get the inverter/charger powered for at least 24 hours, thereby getting the batteries fully charged. There is an issue that some Magnum chargers will not perform optimally since Airstream was not installing the temperature sensor on older Interstates (2013-2015?). It has been reported that Airstream is now installing the Magnum temperature sensor. But getting plugged in is better than relying on solar and engine alternator to get you batteries charged. It is also better than running the generator for a few hours as this does not get a full battery charger cycle.

I hope this helps you understand why people have battery problems with their Interstates as built by Airstream. The fix is reasonably simple and establishes the fact that your Interstate needs to stay close to an external AC power source.

Comments welcome.

[amirm]

I am still learning the systems on my new Interstate. But it sure is a mess electrically. Here is the latest observation: there are no less than three volt meters. Only the Magnum is accurate. The other two drift in different directions. The solar monitor is way off at low voltages. I let the batteries drain very low. The solar monitor said they were at 12.25 whereas Magnum correctly indicated 12.0 volts.

The solar monitor has a pot that lets you adjust the accuracy of its volt meter (horrific to have to rely on such a thing rather than having a stable reference). The problem is, at high voltages of say, above 12.3 volts, it agrees with Magnum and true voltage of the cells. If you adjust it for low voltages, then it will be wrong for higher voltages!

It is remarkable to me that there is not one single battery charge indicator for the whole system. The closest thing to that is the solar monitor which per above, is way off as you drain the batteries. And of course gets totally confused the moment any charging starts and voltage shoots up. It shows "100%" full but that is completely wrong.

As I look at upgrading to Lithium batteries, this whole thing becomes useless as you can't track the power of Lithium cells using their voltage.

Now with OP's post regarding BIM, I have more troubleshooting to do . Thanks for the detailed information.

[LB_3]

Voltage is a nearly useless measure since it varies with current draw and charging status. The only reliable way to keep track of battery status is to use a monitor that keeps track of Amps in and out of the battery.

[lewster]

Originally Posted by LB_3

Voltage is a nearly useless measure since it varies with current draw and charging status. The only reliable way to keep track of battery status is to use a monitor that keeps track of Amps in and out of the battery.

If you're measuring transient voltages, yes due to voltage sag in lead acid batteries. If you are measuring resting voltage, then it's quite useful if you have an accurate way to measure same..........like a good DVM.


Lew Farber
RVIA/RVDA Nationally Certified Master Tech
ABYC Certified Master Marine Electrician
Master Tech Energy Systems, Inc.
AM Solar Certified Installation Center*AMS Lithium Batteries
Lifeline AGM Batteries**Magnum Inverters***Victron Energy Components
541-490-6357

[Boxster1971]

Originally Posted by LB_3

Voltage is a nearly useless measure since it varies with current draw and charging status. The only reliable way to keep track of battery status is to use a monitor that keeps track of Amps in and out of the battery.

I agree 100% - which is why the systems installed by Airstream are so bad.

I added a 500A/50mv DC shunt that provides current in and out of my house batteries. First I had it only displayed on the Blue Sky IPN-Pro Remote display for the solar controller. When adding the Magnum MS2000 inverter/charger I also added the Magnum ME-BMK to insure the charger tracks the battery condition as well as the solar controller.

[Marks71]

Super helpful THX

[lewster]

Originally Posted by Boxster1971

I agree 100% - which is why the systems installed by Airstream are so bad.

I added a 500A/50mv DC shunt that provides current in and out of my house batteries. First I had it only displayed on the Blue Sky IPN-Pro Remote display for the solar controller. When adding the Magnum MS2000 inverter/charger I also added the Magnum ME-BMK to insure the charger tracks the battery condition as well as the solar controller.

Great job on the research! I concur 100% from what I've seen with the PCI BIM. It does interesting things however, when using a page lithium bank and hybrid inverter/charger while running the roof A/C. We have seen up to 60 amps from the engine alternator feeding back in to the house batteries under this heavy load, so it does go both ways.

BTW, We have found that your Magnum will read about 0.1-0.2VDC lower than the Blue Sky iPN-PRO. Just some experiential data from users of these systems.

[amirm]

So isn't one easy solution to disable/disconnect solar charging when the ignition is on?

[Boxster1971]

Originally Posted by lewster

Great job on the research! I concur 100% from what I've seen with the PCI BIM. It does interesting things however, when using a page lithium bank and hybrid inverter/charger while running the roof A/C. We have seen up to 60 amps from the engine alternator feeding back in to the house batteries under this heavy load, so it does go both ways.

BTW, We have found that your Magnum will read about 0.1-0.2VDC lower than the Blue Sky iPN-PRO. Just some experiential data from users of these systems.

Lew - thanks for the tip on the voltage variations. The Sprinter alternator can definitely put out some power when needed. With the loads you describe I'd assume the voltage seen by the BIM is low enough to connect the battery systems and let the alternator supply power to run the A/C.

Having a large lithium bank and a big inverter would really be nice if you needed the coach A/C on while driving on a hot humid day with passengers in the back. Hmmm - you are giving me ideas for my next upgrade. 😄



- - Mike
2013 Lounge EXT on 2012 Sprinter

[Boxster1971]

Originally Posted by amirm

So isn't one easy solution to disable/disconnect solar charging when the ignition is on?

Disabling the solar charging would be one approach. On a stock Interstate system you would probably have to pull out a fuse as there is no switch in the circuit. Although I'm not sure if you can disable the solar that easily. I'd have to research that to be sure.

I just changed the momentary ON Battery Assist switch on left side of driver's dash to an ON/OFF switch with an indicator light. When I want to connect the batteries while driving I just switch the relay ON. This now makes the BIM work a lot like the ML-ACR battery charging relays a from Blue Sea Systems.
https://www.bluesea.com/products/cat...Relays/ML-ACRs

I thought about upgrading to the BSS ML-ACR, but that involved more wiring changes in the long run from the BIM in back of van to the drivers dashboard.

I only connect the batteries for an hour at a time to use the same logic as the BIM circuits. I turn on the switch long enough to get the batteries close to full and let the solar panels finish the job. Here is a photo of my new switch.





- - Mike
2013 Lounge EXT on 2012 Sprinter

[amirm]

Originally Posted by Boxster1971

Disabling the solar charging would be one approach. On a stock Interstate system you would probably have to pull out a fuse as there is no switch in the circuit. Although I'm not sure if you can disable the solar that easily. I'd have to research that to be sure.

My thought was to build my own solution. So far with my limited experience, I have not noticed the problem you see. The engine in a one hour trip nicely charged the batteries.

I just changed the momentary ON Battery Assist switch on left side of driver's dash to an ON/OFF switch with an indicator light. When I want to connect the batteries while driving I just switch the relay ON. This now makes the BIM work a lot like the ML-ACR battery charging relays a from Blue Sea Systems.
https://www.bluesea.com/products/cat...Relays/ML-ACRs

I thought about upgrading to the BSS ML-ACR, but that involved more wiring changes in the long run from the BIM in back of van to the drivers dashboard.

That's pretty clever.

I really wish there was a nice dashboard display that gave full status of the systems in the back.

[Boxster1971]

Originally Posted by amirm

My thought was to build my own solution. So far with my limited experience, I have not noticed the problem you see. The engine in a one hour trip nicely charged the batteries.





That's pretty clever.



I really wish there was a nice dashboard display that gave full status of the systems in the back.

How do you know your batteries are getting fully charged when you drive? Unless you have a way to measure true current flow into and out of your coach batteries you are relying on the voltages shown. Those voltages are not an accurate picture of your battery state of charge. You are likely getting some charge but my point is the Airstream installed electrics will slowly kill your batteries by only providing a partial charge. The fix is to get it plugged into shore power every few days so the Magnum charger can give the batteries a full charge.

I may be too cleaver for my own good. Yesterday I noticed the little LED indicator I installed on the main control panel for BIM status was not working. I used a 5V LED because that is close to the hold voltage I measured when BIM closed the connection relay. However now I realize when I use my dash switch that LED gets a full 13+ volts. I probably burned it out with the over voltage. Now I'll need to fix it. By the way you can also tell when the batteries are connected by checking the voltage on the tank monitor panel. If they are the same the batteries are connected. Here is photo of my main control panel.



- - Mike
2013 Interstate Lounge EXT on 2012 Sprinter

[toskeysam]

Engineers never stop tinkering......just look for ways to "enhance" ....at least that's what my wife keeps accusing me of. Hope none of us lose that instinct....if so, it's "game over". 😊

[rmkrum]

It's just a manifestation of "The knack".

Look for the video clip of that name from the Dilbert show.

Then don't tell me Dilbert is NOT a documentary 😀😀😀


Sent from my iPad using Airstream Forums

[Boxster1971]

Originally Posted by Boxster1971

Disabling the solar charging would be one approach. On a stock Interstate system you would probably have to pull out a fuse as there is no switch in the circuit. Although I'm not sure if you can disable the solar that easily. I'd have to research that to be sure....

I looked at the Interstate wiring diagrams for the solar today. There are inline fuse(s) and a thermal circuit breaker in the solar system. None of them are easily accessible. I've attached the basic solar wiring from the 2015 Interstate Owner's manual and a snip from the main 12VDC diagram in the same manual. They don't even show the same fuses and connections to the thermal circuit breaker. You would have to verify the wiring in any specific Interstate to know how it is actually wired.

[Mcrid]

Mike,

For my '16 GT, the Solar Circuit Breaker is behind the Breaker Panel wall below the DS Jump seat. It came with a 15 amp breaker and I changed to a 20 amp when I went with 300 Watts of solar. There is sufficient room to install a disconnect switch for the Solar if one desires. I see your point on the BIM so I may just install a solar disconnect. I'd rather forget to turn the Solar on than forget to turn the BIM off!!

[Boxster1971]

Originally Posted by Mcrider

Mike,

For my '16 GT, the Solar Circuit Breaker is behind the Breaker Panel wall below the DS Jump seat. It came with a 15 amp breaker and I changed to a 20 amp when I went with 300 Watts of solar. There is sufficient room to install a disconnect switch for the Solar if one desires. I see your point on the BIM so I may just install a solar disconnect. I'd rather forget to turn the Solar on than forget to turn the BIM off!!

A switch to disconnect the panel energy before the controller is very desirable. Attached is a diagram from AM Solar that I used when installing my solar upgrade. I used one of the BSS 500A switches that Lew Faber recommends. It's also handy if you need to work on the electrical system in daylight because you can stop the solar energy from powering the system.

[73shark]

Originally Posted by Mcrider

Mike,

It came with a 15 amp breaker and I changed to a 20 amp when I went with 300 Watts of solar.

Is the existing wiring sized for 20 amps.

[Mcrid]

Originally Posted by Boxster1971

A switch to disconnect the panel energy before the controller is very desirable. Attached is a diagram from AM Solar that I used when installing my solar upgrade. I used one of the BSS 500A switches that Lew Faber recommends. It's also handy if you need to work on the electrical system in daylight because you can stop the solar energy from powering the system.

Mike, I looked at the BIM wiring diagram and it would be easy to wire a relay into the ignition input on the BIM and use a NC relay on the solar input. Then no switches required. Ignition on solar off.

[Mcrid]

Originally Posted by 73shark

Is the existing wiring sized for 20 amps.

According to AS wiring is fit for 300 Watts. It is 10AWG according to the drawings so just fine for 20+ amps with an acceptable voltage drop.