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Lithium Batteries (from ML-ACR DUVAC Thread)


Jim Bob
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Have been following this thread for a while now and had plans to do the ML ACR swap on my 95.  I just returned from a week of camping at the Bristol NASCAR race and noticed my house batts were no performing all that well.  Once I got home and inspected I had two cables that had become a little bit loose.  So I fixed those, but the batts are fairly old and not sure they are going to recover.  I'm now investigating switching to Lithium iron.  I currently have 4 6v with 75 AH each, so my rudimentary knowledge of batteries tells me I have about 150 AH available to me.  An upgrade to Lithium could get me about 200 AH for slightly more money, but they are supposed to last for 10 years.  The money seems to make sense, but the real advantage is the faster recharge rate compared to FLA.  I switched out my inverter and it has a lithium setting so I think that will work.  So, finally a question.... felt like you needed some background.  If I install the ML ACR and have lithium house batteries and FLA chassis batteries is the ML ACR "smart" enough to know not to charge the FLA batteries to fast?  Is there something else I should do if I go with the ML ACR and Lithium house batts? 

Thanks in advance.

Jim

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I've looked at the Li BIM 225, but now I'm confused as to how and where it would be placed in the wiring set up.  Do I still use the ML ACR and the Li BIM 225?  I suppose I could use only the ML ACR and manually separate the house and chassis batts when I need to recharge the house only?  I also think I'll check with the inverter manufacturer and see what their recommendation would be.  Thanks Van.

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A little late in answering but the ML-ARC is simply a switching device the combines both the chassis and house batteries.  It can be left in automatic, which will combine both bank if it senses a charging source, which could be the inverter (powered by either shore or generator) or the alternator.  It can also be operated manually and left off or on.  Adding the switch at the dash provides convenience

I have solar that charges both banks of batteries.  z

I was also considering lithium batteries but decided to hold off for now.  From my understanding the lithium requires a higher charging voltage and has the potential of overloading the alternator.  There would have to be some other controllers installed to accomodate lithium and at this point I'm not interested in going that route.  

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No worries Jim J.

The more I've explored the Lithium the better they sound to me.  Particularly the much quicker charge time they have versus the lead acid battery.  However, they do seem to complicate things.  I've emailed the inverter/charger manufacturer to see what they have to say regarding mixing the two types.  At this point, I think I could make the ML ACR work by using the manual switch to disconnect the chassis when I need to just charge the house batts.  Would just end up being a more manual process than an automated one, but will see what they say.

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22 hours ago, Jim Bob said:

No worries Jim J.

The more I've explored the Lithium the better they sound to me.  Particularly the much quicker charge time they have versus the lead acid battery.  However, they do seem to complicate things.  I've emailed the inverter/charger manufacturer to see what they have to say regarding mixing the two types.  At this point, I think I could make the ML ACR work by using the manual switch to disconnect the chassis when I need to just charge the house batts.  Would just end up being a more manual process than an automated one, but will see what they say.

I'm coming into this conversation late, as it has evolved from DUVAC - SSI, IRD, BIRD alternator problems to Lithium battery charging from the alternator.  It would be better served to have this as a new post, because the information is likely going to useful to others, but hidden in a non-related post.  First, the very basic - the stated purpose:  "The ML-Series ACR automatically combines batteries during charging, and isolates batteries when there is no charging sensed on either battery bank".  That's all it does.  It doesn't have specific charge profiles, but uses whatever profile is used at the charging source. 

The alternator is one charging source.  The alternator charge profile (if it can be called that) is constant voltage charging at approximately 14.2-14.4 volt - as long as it can (the engine is still running, and the alternator or its system has not be overloaded or compromised).  Note that there are no provisions to sample State of Charge (SOC) of the chassis battery and not provisions to switch from Bulk, to Absorption, to Float.  It stays at 14.4 volts - period.  

The other charging source for most of us is our Inverter/Charger.  That source does have selectable and sometimes customizable charge profiles.  Most of us have it set to either Lead Acid wet cells (i.e. Trojan) or AGM (i.e. Lifeline) batteries.  The charge profiles are selected for the House Batteries.  

Now, the ML ARC simply connects the two sets of batteries together.  Granted it does so under specific conditions, and keeps them connected based on specific conditions, but for the sake of this discussion, those conditions don't matter.  We are only looking at 1) They have met the conditions and are Connected, or 2) they have not met the conditions and are Not Connected.  The Not Connected condition is just that, and shouldn't require more discussion.  It is the Connected condition that matters.  

When the alternator is the source, it is producing 14.4 volts (approximately) and if the ML ARC state is Connected, then the Chassis and the House batteries are being exposed (charged if not already charged) to 14.4 volts.  This is quite normal (maybe not ideal, but typical) for the Chassis battery.  But, having the House battery at 14.4 volts is like have a Battery Charger set permanently to Absorb, as long as it is connected.  This will eventually lead to out-gassing and boiling out the water.  We seem more concerned about House batteries because they cost more in the scheme of thing.  This likely isn't a problem for a trip of under 4 hours.  But if you are driving 8-10 hours a day, especially several days in a row, this is not ideal for the house batteries.  Right now, I'm talking wet-cell and AGM - NOT Lithium.  As long as the water is watched, it likely won't cause significant loss of battery life unless you're on the road an awfully lot.  Now consider Lithium Batteries for house batteries.  Charging them at 14.4 volts, for even over an hour per 100 AHrs rating (designated "C" for Capacity) is detrimental. Most here will likely have 2) 100 AHr  or 1) 200 AHr Lithium battery.  Some will have more.  So, for a total of 200 AHrs, we start causing damage charging for more than 2 hours (1 Hr X C) where C is 200AHrs in this example.  You can see that it would not be unusual to double or triple or more this value while driving.  That is to be avoided.  Remember, we are speaking at this time only charging by the Alternator when both sets of batteries are Connected.  Another attribute of Lithium batteries is that they will accept charge much faster than wet-cell or AGM batteries.  It is not uncommon to charge them at a rate equal to "C" (Capacity).  In our example above, that would mean 200 Amps!  And they will accept that 200 Amps until full.  If you remember, wet cells and AGM require a Bulk, Absorb and Float profile to SAFELY reach full charge.  In the Absorption Mode, the current is slowly tapering down to a value around 3% - 5% "C" (which would be 6 -10 Amps, and then switch to Float for the last 10% - 20% of fully charged.  Since the current tapers off quickly, the alternator will seldom see a max of 200 Amps for any length of time.  This is important because the Alternator is not rated at is max output for 100% duty cycle.  This is the primary reason (but not the most important reason) that people who install Lithium House batteries are concerned regarding charging from the alternator (few are really knowledgeable about the sustained exposure to high voltage concern).  There is no way that the ML ACR can control this.  That is not what it was designed for.  Yes, you could disconnect the chassis batteries from the alternator, which would lower some of the load on the alternator (in an attempt to not burn it up), but that wouldn't solve the high voltage problem. 

The only real solution for Lithium installations is to install a DC-DC Charger such as the Victron Energy Orion-Tr Smart DC/DC Charger. This is a 3-stage that uses the alternator voltage as the input.  It operates very similar to the Battery Charger we have for shore power.  It is designed as a solution to a variety of problem.  We won't discuss the "Smart Alternator" solution, as it isn't applicable to our coaches. It will take the alternator voltage and use it to charge the house batteries, at the proper charge profile, whether wet-cell, AGM, or Lithium.  It will also limit the current (and therefore the load) on the alternator.  I don't think (I need to more research since I don't use it that way) allow charging the chassis battery when on shore power.  So, it may be that some will want both a ML ARC and a DC/DC Charger.  The solution I am using is to inhibit my BIRD, such that it will never connect the two battery banks together, except from the Dash BOOST switch, in any case.  The alternator can not charge the house batteries, and the house batteries cannot charge the chassis batteries.  I have 1400 watts of solar.  I have the original Monaco panel (90-100 Watt) panel designated with it's own solar controller to charge the chassis battery.  The rest of the solar goes through two MPPT controllers that charge only the House batteries.  I can select the charge profile for all three solar controllers.  I am currently building Lithium batteries, but I did this just to save the Lifeline AGM batteries.  I may get a DC/DC charger for the Alternator is I find the solar isn't enough (along with shore or generator power through the main battery charger) to keep the house Lithium batteries charged.  Note that charged means something different in Lithium batteries.  You do not want to charge to 100% unless you are going to use it immediately.  You never want to store Lithium with over 80-85% charge.  This is to maximize battery life.  The sweet spot with Lithium batteries is between 20% and 80% SOC.  So you want to be able to shut off charging when it reaches approximately 80% SOC, not 100%  That is something you can't do without a smart charger. 

There are many more considerations, most not obvious, and some not even mentioned by battery manufacturers, that should be considered when switching to Lithium Batteries.  I think this is enough off-topic for this thread. 

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Waterskier 1

Thanks for the detailed response. 

When I first considered lithium I started to do research and found there was much more to it then simply putting in a lithium battery.  I knew that charging was more complicated.  Also read about the alternator issues.  Also read about cold weather protection including temperature controlled heating if in cold weather.

I don't do enough boon docking to justify the time and expense.  It's just easier for me to start my generator for ~1 hour a day to keep the batteries up. 

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Jim J,  quoting waterskier "wet cells and AGM require a Bulk, Absorb and Float profile to SAFELY reach full charge".  I would not even consider lithium if I only had to run the gen for an hour.  However, my experience is that it takes 6 hours or more to get even close to full charge via generator.  That is a pain in the you know what.... hence my consideration of Lithium.  My FLA batts are still going and I don't have another boon docking trip planned until Spring...  so I've got time to research and ponder.

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Waterskier (Rick?)

I think the Lithium battery subject does indeed deserve its own thread.  I think Walter had started one.  Perhaps you can start another or join Walter's original thread.  I find the Lithium battery subject quite fascinating.  But like Jim, I would have to understand it a lot more thoroughly before I dump my 1000 AH FLA (8 T-145 size 6V batteries) and switch to it.  You, and several others, seem to have PERSONAL experience with the subject.  As Bill D famously said (ad nauseum) "Don't tell me what you read on the Internet.  Tell me what YOU have done."

Some of you guys with PERSONAL experience in converting to Lithium batteries could do the rest of us peons a great service by keeping us informed of your progress, experiences, and your thoughts.

By all means, do start a new thread.  And not because your contributions aren't welcome on this one, but with "DUVAC" as the heading of this thread, it would be harder to search for info on Lithium batteries.  Perhaps Scotty could "cut and paste" to save some of this Lithium info to a thread devoted to it.

Thanks so much for your detailed input!!  At present, all I can add is QUESTIONS.  Some of you guys have ANSWERS.  Thank you!

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