Intelligent Battery Management

turbopilot

New member
My 2016 Unity MB electrical system is currently equipped with two LifeLine AGM house batteries (220ah), 5 GoPower 100 watt flex panels (up to 500 watts output), 100 ah AGM cab battery and Intellitec Isolator Relay.

The Intellitec Isolator Relay (IIR) is a "low cost" approach to managing multiple batteries. So while the device is cheap "i.e. low cost" it seriously restricts your ability to intelligently manage the batteries and electrical system in the Unity.

The IIR connects the house electric system to the cab electrical system. The device lives under the passenger seat. It's operation is very simple, it looks for the voltage on the cab side to rise above 13.1 volts for 12 seconds, then it closes the connection between the house and cab electrical system. The device does not care what the voltage is on the house side and it provides no options to connect the two sides unless the voltage on the ignition circuit is higher than 13.3v for 12 seconds.

Given the capability of my Unity electric system (particularly the addition of up to 30 amps of solar power) I made the decision to upgrade the IIR and replace it with a Blue Sea ML-ACR Automatic Charging Relay. The ML-ACR is available on Amazon for $202.94.

The Blue Sea ML-ACR offers many advantages over the simple IIR. The ML-ACR has three modes: OFF, Automatic Combine and Manual Combine. In the OFF mode the relay disconnects the cab and camper electrical system. In the Manual Combine mode the ML-ACR connects the two electrical system with a manual switch controlled by the operator.

The magic in this device is the Automatic Combine mode. In this mode the device will automatically connect the two electrical systems any time it senses voltage on either side (cab or camper) to be above 13.5V for 30 seconds or 13.0V for 90 seconds. Likewise the ML-ACR in the Automatic Combine mode will disconnect the cab and camper electrical systems anytime the voltage on either side is below 9.6V(under voltage lockout), below 12.35V for 10 seconds, below 12.75V for 30 seconds or above 16. 2V(over voltage lockout).

In the Automatic Combine mode the ML-ACR is basically looking at voltages on both the camper and cab side of the electrical system and combines the electrical systems any time the voltages are compatible with one or the other electrical systems being charged (i.e. charger, solar or cab alternator).

Here are some images of the exchange of the IIR for the ML-ACR.

This is the passenger seat pedestal. Note the installation of the awing LED and awing in/out switch was not very "fancy".



Here is a closer look at how the switches were installed:



Here is a look at the IIR as installed by LTV in the passenger seat pedestal. The solenoid and IIR controller are mounted on the board. Note cables are just held down with aluminum tape :bash::



Here is how it looks after the Blue Sea ML-ACR is installed and the installation cleaned up:



And finally I took the opportunity to "upgrade" the switch panel on the side of the seat pedestal to include the ML-ACR control switch and provisions to monitor cab voltage when the ignition is on:



I had a Blue Sea ML-ACR in my last RV so I thought I would share some circumstances where this device provides all sorts of extra options for battery management in normal and abnormal camper operation.


- The ability to disconnect the cab from the camper for long drives during daylight. The will allow the intelligent GoPower Solar Controller to charge the house batteries avoiding overcharging the house batteries using the "dumb" cab alternator.

- The ability to use all batteries for occupied camper operation (house+cab=320ah of capacity). Can be risky but with the Magnum and Jennsen battery alarms you should never totally discharge all the batteries. In the worst case given the design of the system all you need is enough juice to start the generator to bring everything back to life including the cab to start the engine.

- The ability to drive the camper in the event of an alternator failure. Between the cab/house house batteries and the solar system there should be no problem driving the camper indefinitely during the day time with the alternator inop.

The ability to start the MB cab engine in the event of a cab battery failure or inadvertent discharge. Simply manually combine the cab and house systems and let the camper batteries start the truck.

- During daylight hours when operating on solar alone you will hear the ML-ACR cycle on and off as either camper demand for juice and/or falling solar output conspire to bring the house batteries below 12.75v for 30 seconds. When this happens the ML-ACR automatically disconnects the cab from the camper electrical system to preserve the charge on the cab battery. When conditions change (i.e. lower camper demand and/or higher solar output) the relay will reconnect the two sides automatically.

- For long term outside storage this arrange allows both the camper and cab batteries to be intelligently charged via the solar panel controller.


So as you can see this simple device makes the entire cab/camper electrical system much more robust to deal with all sorts of planned and unplanned events that can happen on the road.
 
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Peter Tourin

2020 Unity RL, ex 2012 Unity MB
That's very cute! - seems really nicely thought out, and I hope my install work looks as clean as yours.
 

SSTraveler

2014 LTV Unity Murphy Bed
Really nice job! Thanks for the pictures, I have been wanting to move those awning switches and didn't want to open a can of worms not knowing what all is under the passenger seat. I hate the location of these switches, not very convenient, especially the light switch, which might be used multiple times at night for the lighting.
 

turbopilot

New member
Really nice job! Thanks for the pictures, I have been wanting to move those awning switches and didn't want to open a can of worms not knowing what all is under the passenger seat. I hate the location of these switches, not very convenient, especially the light switch, which might be used multiple times at night for the lighting.
I agree. I thought about moving all the switches to the overhead console in the cab just above the reading lights. But I could not figure out how to pass a large wire bundle up to that area without tearing out a lot of trim.

The Blue Sea ML-ARC is only about $100 more than the IIR and adds so much important functionality, I can't believe LTV does not include the device as standard equipment.
 
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turbopilot

New member
Very nice.
I'm waiting for my 2016 TB to be delivered. I didn't get the generator, instead got the 270 amp aux alternator with fancy regulator. http://www.nationsstarteralternator...tor-Kit-with-270-Amp-p/sprinter-dak-270xp.htm
I'm looking for places inside to install "stuff" and this looks a great place. As mentioned before, I live 10 miles from AM Solar and will be working with them for my "dream" power supply system.
I look forward to following the progress of your systems in the TB.
 
It appears that you replaced all three camper/cab batteries and that they are all AGM but it looks like they are of different ah capacities. Does this matter or is it only important that they are are all the same type of battery? I like what you have done (very nice work). You added three more flex solar panels which I assume is essentially plug and play after cleaning and glueing. Does the 2016 come with enough connectors for three more panels? I thought that I saw somewhere that the plug in connector on top of the camper had four spaces for plug in?? Also, wouldn't this work with the original new camper batteries? This is something I could do myself "except" sorting out the new wiring under the seat. I'd probably have to take it to someone to have that done so that I didn't do any unintended welding under the seat.... ;-)

Thanks, Bob
 

turbopilot

New member
It appears that you replaced all three camper/cab batteries and that they are all AGM but it looks like they are of different ah capacities. Does this matter or is it only important that they are are all the same type of battery? I like what you have done (very nice work). You added three more flex solar panels which I assume is essentially plug and play after cleaning and glueing. Does the 2016 come with enough connectors for three more panels? I thought that I saw somewhere that the plug in connector on top of the camper had four spaces for plug in?? Also, wouldn't this work with the original new camper batteries? This is something I could do myself "except" sorting out the new wiring under the seat. I'd probably have to take it to someone to have that done so that I didn't do any unintended welding under the seat.... ;-)

Thanks, Bob
Based on my experience in another RV, I don't think it makes a difference that the AGM batteries have different ah capacities. If it does make a difference I never noticed it in 5 years of operation.

Yes, a total of 5 Flex panels on the roof. Each panel comes with a "piggy back" connector so you can add any number up to 5 panels which is the capacity of the controller.

Original camper batteries are lead acid. So you at least want the same time battery to match charge and solar controller set up.

With this set up it will allow me to "harvest" some of the cab batteries ah if I ever need it to supplement the house batteries. As long as there is enough juice between the 3 batteries to start the generator, then all the batteries including the cab batteries can be charged up by the generator with this set up.
 
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Based on my experience in another RV, I don't think it makes a difference that the AGM batteries have different ah capacities. If it does make a difference I never noticed it in 5 years of operation.

Yes, a total of 5 Flex panels on the roof. Each panel comes with a "piggy back" connector so you can add any number up to 5 panels which is the capacity of the controller.

Original camper batteries are lead acid. So you at least want the same time battery to match charge and solar controller set up.

Will this set up it will allow me to "harvest" some of the cab batteries ah if I ever need it to supplement the house batteries. As long as there is enough juice between the 3 batteries to start the generator, then all the batteries including the cab batteries can be charged up by the generator with this set up.


Thank you for the information. Now I better understand how the roof solar panels connect. My goal is to add two more of the flex panels AND allow for me mounting a small 12v wind generator to the ladder on the back so that when I spend time camping along the gulf coast I'll get a small charge 24/7 instead of just during the day. At least I "think" this ought to be workable. All I have to do is to attach the proper male plug to the wires from the wind generator to plug into the solar array?? At least that is my plan at this point... ;-) First I'm going to see if Leisure will put two additional flex panels on top when they build my camper in May!
 

turbopilot

New member
First I'm going to see if Leisure will put two additional flex panels on top when they build my camper in May!
Suggest you do it yourself when you get the rig. Save some money and make sure the orientation of the panels is most efficient for future expansion. Very easy to install once the first two panels are there along with the install/wiring of the controller is in place.
 

wade5979

New member
What is your voltage reading on the camper side after replacing the IIR. On my 2016 MB I have 14.2 on the cab battery but then it drops to 13.9 after coming through the IIR. I would like to see 14.2 on both sides.
 

Peter Tourin

2020 Unity RL, ex 2012 Unity MB
That does sound odd - when I check my battery monitor while idling or driving, I see right around 14.2 at the battery. It may well depend on what year, as I gather that the M-B charging/regulation systems have been changing - my rig is a 2012 - if yours is newer or older you may want to have others chime in also.
 

turbopilot

New member
What is your voltage reading on the camper side after replacing the IIR.
It depends. There are so many variables that impact the voltage level once the camper and cab electrical systems are combined via ML-ACR. On the camper side with PV panels the solar controller will be trying to run its algorithms for charging while camper loads are fluctuating. So the system voltage will depend on what stage the the solar controller happens to be and the loads on the bus.
 
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andrewj

Member
For reference I found my solenoid under driver seat and IRD was in battery compartment in my 2012 chassis. There are two control wires running from the driver seat area to battery area, however only one was used. Before my 2013 ltv year some of the older units had a Bidirectional IRD that probably used both of the wires. With the BIRD you can use a panel switch to bridge all batteries to start the engine, similar to the ML-ACR. Mother Benz told them they cannot connect back to the chassis supposedly, so they dropped that option. The ML-ACR is a much more flexible solution, thanks for the write up.

I was ready to upgrade to the Ml-ACR to fix my charging problem, but in prep i traced the correct wire on the IRD and just jumpered it to the battery 20 times to exercise the sticky solenoid and my charging issues appear solved....

Side benefit of this dyi educational effort is now I know how simple it is to simply jumper the IRD/solenoid wire to manually connect both batteries in an emergency.

The ML-ACR is a really nice item and they do make one without the manual override yellow switch for a few bucks less. Since the solinoid is under the driver seat in 2013, i can not reach it to mannually override, but it looks like you can.
 
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turbopilot

New member
Side benefit of this dyi educational effort is now I know how simple it is to simply jumper the IRD/solenoid wire to manually connect both batteries in an emergency.
Lot's of variation in the wiring by model year. But yes, for anyone in an emergency who can find there IRD solenoid all they need is to place +12v on the small terminal of the IRD solenoid to combine the cab and camper electrical systems.

For the ML-ACR and the optional PV panels there is a good reason have a manual switch. During the summer with good PV panel output it is really a good idea to not combine the electrical systems when driving. Instead let the PV panels recharge the house batteries rather than have two charging sources (one smart and one dumb) charging all the batteries at the same time.
 

Peter Tourin

2020 Unity RL, ex 2012 Unity MB
I've got the BIRD with the dashboard switch - I even had to use it twice before I started remembering to turn the radio off. You leave it on for the side and backup cameras, then walk away and forget...

I'm going to want to do just the opposite - I need to interrupt the line that combines the batteries when my LiFePO4's are fully charged - there's a debate about whether constant charging after they're full is harmful, and they're too expensive for me to find out the hard way. So when my battery monitor says they're full, it'll kick a double pole relay that opens the IRD line and also opens the AC feed to the charger - easy way to control charging.
 

casdclassb144

New member
I have been working with Flex panels 2 years ,They degrade lots, water sits in them and need constant cleaning , Test a 100 watt regular panel against a flexible panel 2 years old They are great if this the only option you have
 

andrewj

Member
Turbo, i have wondered how the MB voltage regulator and solar charger resolved conflict since there is no logic circuit to communicate. When the dumb solinoid opens after you start the van, all batteries become interconnected. The smart solar charger is trying to bulk/absorb/float according to a battery friendly plan and according to Pete, the MB charging system is mainly trying to keep the chassis battery optimized.

http://www.sprinter-source.com/forum/showthread.php?t=42013

So, what is best when driving with solar on a sunny summer day. Disconnect it and let the engine door a poor job of charging the house, disconnect the main connection to the engine, or just leave both sources connected?
 

turbopilot

New member
So, what is best when driving with solar on a sunny summer day. Disconnect it and let the engine door a poor job of charging the house, disconnect the main connection to the engine, or just leave both sources connected?
I have had a lot of practice with this for the last 5 years since my previous RV had a very similar setup. If you begin a day that will involve a lot of driving you look at the SOC of the house batteries and make a guess about how sunny a day it will be. If it looks like you can get enough sunlight during the day to top off the house batteries (most likely case in the summer with short nights and a lot of sun), then turn off the ML-ACR and let the solar controller "smartly" top off the house batteries and the cab alternator handle the cab battery until you are done driving then put the ML-ACR into automatic mode.
 

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