Lithium 80% DOD rule

[Davydd]

Originally Posted by cruising7388

I guess it's in the eye of the beholder, but IMO, considering the level of sophistication of the ARV electrical system design, it seems puzzling that in the event of a BMS shutdown, you have to keep your finger mashed to a reset switch for a couple of minutes to bring the BMS out of a coma.

A seldom needed function? Perhaps for you because you understand your system and don't let this condition arise in the first place. For those less familiar with or less interested in their battery system, or not equipped with an autostart feature, my guess is that it will happen a lot.

In the Etrek, as far as I know, the Roadtrek AGM services no coach loads and is there solely to provide bringing the BMS back to life which apparently it does faster than the ARV system. How it's accomplished is unexplained and in fact, there is no explanation of how this battery is kept charged, i.e. by which alternator or whether it ever sees shore power support.

Since you have the contact, I'd appreciate learning what actually happens electrically in your setup when you press and hold the reset switch.

I guess you didn't understand it has never happened in nearly 2 years and 44,000 miles of RV travel other than my deliberate curiosity testing. There is no need for backup AGM batteries to save a few minutes if it ever did happen. Advanced RV provides owners with much more battery status information as I described beyond idiot lights that any ARV owner can understand. Sometimes the KISS principle applies and adding two AGM batteries is not KISS.

[cruising7388]

Originally Posted by gregmchugh

In the most common Roadtrek configuration here is how the AGM is wired into the system and gets charged.

The AGM is connected to the charge terminal on all the Ecotrek modules along with the underhood generator and the solar charge controller.

The inverter/charger and the 12v loads are connected to the load terminal on all the Ecotrek modules.

The AGM, therefore, is always being charged by the underhood generator and the solar charge controller.

At any time when at least one Ecotrek is online with both the charge and load relays closed then the AGM is also connected to the inverter and the 12v loads and is simply in parallel with the Ecotreks. In this case, if on shore power, the AGM also gets charged in parallel with the Ecotreks by the charger in the inverter.

Thanks for the input. If I understand your analysis, I end up with two questions:

If the AGM is paralleled with the lithium batteries, isn't it subject to discharge from supporting coach loads and further, isn't the depth of the AGM discharge controlled by the 80% DOD levels of the lithiums? And, when the lithium batteries shut down, what disconnects the paralleled AGM from the coach loads to ensure it remains in the condition necessary to support a lithium battery reset?

If the AGM is recharged by shore power, uh generator or solar panels, or some combination, is it detrimentally affected by the charging profile used for lithium batteries which is different from the optimum charging profile for an AGM?

[gregmchugh]

Originally Posted by Davydd

I guess you didn't understand it has never happened in nearly 2 years and 44,000 miles of RV travel other than my deliberate curiosity testing. There is no need for backup AGM batteries to save a few minutes if it ever did happen. Advanced RV provides owners with much more battery status information as I described beyond idiot lights that any ARV owner can understand. Sometimes the KISS principle applies and adding two AGM batteries is not KISS.

Not that it will likely matter in terms of opinions on the value of an AGM battery in a lithium battery van, I will simply point out once again the fact that Roadtrek is currently installing a single AGM 12v battery of 100AH or so, not two AGM batteries. That is the configuration in all recent deliveries but it is a fact that there are some older vans where they installed two.

I like to have the facts out there...

[Davydd]

For turning our Outback inverter (same as Avanti's) on and off it is a simple touch screen button on the Silverleaf monitor. Lifting the cabinet door of the Silverleaf panel gives access to the Outback Mate controller for more detailed use beyond my understanding unless I want to read my 128 page detailed manual.

Having the battery capacity, I have already described why I choose to leave it on for transparency and use of my RV with all electrical functions live all the time no matter whether I am plugged into shore power or boondocking. I can guarantee that transparency will make you want to avoid private campgrounds as much as possible and extend your ventures to more areas than you can imagine like camping in an alley behind a mansion in Newport, RI for two nights or on a street in Queens, NY.

BTW, I have the first generation of lithium ion batteries ARV installed beyond a brief trial of Smart Batteries. They now have a newer generation I understand with some redundancy as I learned meeting up with "Gustav" in Grand Marais, MN this week. They are also installing different inverters I think and as you know I jumped at the chance to upgrade to the Delco-Remy 320 alternator last May. They aren't standing still. They are a company that pursues the best they can find and provide without competition pricing and dealer constraints. I haven't been there since last May so maybe have no idea what they are up to today, and in ARV time that is a lot. Heck, for all I know they may have an improvement for what Cruising7388 is critical of. Trust me. I am not privy to what they are up to unless I visit their facility. Then they are open to everything they are up to. That's why I suggest you go to their Advanced Fest in May whether you have an ARV or plan to buy one or not. A lot of non-ARV owners have done so like James and Stef of FitRV and you can learn a lot.

[Davydd]

Originally Posted by gregmchugh

Not that it will likely matter in terms of opinions on the value of an AGM battery in a lithium battery van, I will simply point out once again the fact that Roadtrek is currently installing a single AGM 12v battery of 100AH or so, not two AGM batteries. That is the configuration in all recent deliveries but it is a fact that there are some older vans where they installed two.

I like to have the facts out there...

Last spring it was two 6v AGM batteries under the hood.

[gregmchugh]

Originally Posted by cruising7388

Thanks for the input. If I understand your analysis, I end up with two questions:

If the AGM is paralleled with the lithium batteries, isn't it subject to discharge from supporting coach loads and further, isn't the depth of the AGM discharge controlled by the 80% DOD levels of the lithiums? And, when the lithium batteries shut down, what disconnects the paralleled AGM from the coach loads to ensure it remains in the condition necessary to support a lithium battery reset?

If the AGM is recharged by shore power, uh generator or solar panels, or some combination, is it detrimentally affected by the charging profile used for lithium batteries which is different from the optimum charging profile for an AGM?

If you look at the discharge curves and data in the previous posts you will see that the battery voltage at 80% discharge for the Ecotreks is above the voltage where the AGM would be at 50% discharge so it would seem that the AGM is not at risk of deep discharge. When all the Ecotreks have shutdown there is no connection to the load side of the system from the charge side where the AGM is connected.

If you are not familiar with the configuration of charge and load relays in a lithium battery system take a look in this manual. The setup in the manual is for the BMS used in the Advanced RV system but there is a similar setup inside each Ecotrek module.

http://elitepowersolutions.com/docs/...n%20Manual.pdf

In terms of the charging profiles used in the 3 chargers in the Roadtrek design, I think you might find that they are not using lithium charge profiles (typically a constant voltage profile around 14.4 volts as I recall) but they are instead using AGM charge profiles. At least that is my conclusion based on owner reports of the charger settings...

Posting of facts and/or opinions and/or conjectures about the results of using AGM charge profiles on mixed lithium and AGM battery banks may commence now...

Being a software engineer by trade and not an electrical engineer I have my uneducated idea of what might happen but I would prefer an analysis by someone with more expertise to weigh in...

There is a published paper out on the internet somewhere that looks at mixed battery banks in telecommunications systems with some actual test results. I will post a link when I find it...

Could not find a link to that paper but did find this one...

http://radio.feld.cvut.cz/conf/poste...Christiane.pdf

[gregmchugh]

Originally Posted by Davydd

Last spring it was two 6v AGM batteries under the hood.

Now it is one under the hood on Sprinters or one under the rear on Promasters or one somewhere on the Chevies but I don't recall where it is...

[cruising7388]

Originally Posted by Davydd

I guess you didn't understand it has never happened in nearly 2 years and 44,000 miles of RV travel other than my deliberate curiosity testing. There is no need for backup AGM batteries to save a few minutes if it ever did happen. Advanced RV provides owners with much more battery status information as I described beyond idiot lights that any ARV owner can understand. Sometimes the KISS principle applies and adding two AGM batteries is not KISS.

No, what I really don't understand is how someone as intelligent as you clearly are, can cavalierly extrapolate your personal modus operandi to the general RV population where technical Brahmins are in the clear minority if not a rarity.

I'm both surprised and delighted that RT has presumably provided me with not one, but two AGM batteries although crawling under the coach, truth to tell, I can find only one.

Your trotting out the KISS principle cracks me up. You waste no words criticizing Roadtrek's less than perfect execution which is fair dinkum. It's well deserved. But when you are faced with the observation that the ARV battery setup has a wart of its own, you're disposed to turn an admittedly minor flaw into a virtue by invoking the KISS principle. Sorry, but that dog ain't gonna hunt. A two hundred thousand dollar coach shouldn't require the owner to keep your finger plastered to a reset switch for 2 - 6 minutes to waken a shut down battery out of its coma.

[mojoman]

For those who truly want a KISS system to manage a lithium battery pack for $75, this one will allow you to connect any type of non lithium 12v charger to the pack, and shut it off when the first cell reaches the high voltage cutoff setting. It doesn't have a fancy screen but it has worked fine for me.
http://cleanpowerauto.com/files/Mini...istributed.pdf

[booster]

Re the AGM battery potential problems.

As Greg points out, the lithium voltages are higher so the AGM won't severely discharge until after the lithiums are all done, which should be very uncommon or impossible. Any troubles with the AGM will likely be from chronic overcharging, as the power sources will be constantly attached to it, and even the lithium battery voltages are higher for much of the range than AGM likes for float. Imagine that poor AGM, that is already full, seeing 5 cycles of full charge voltage off the engine generator, in only a few hours of Voltstart, and then going on a 5 hour drive still charging.

Of course, this is nothing new in RVs, as the battery systems have always been hooked up this way, leaving them vulnerable to overcharging under various conditions, and undercharging during others. It is why you will probably never see a set of RV batteries last anywhere near the rated number of cycles, or more accurately "lifetime total usable amp hours".

I think the article Greg talked about concerning mixed batteries was for stationary power backup, with essentially perpetual float, so probably not a very good indicator of what will happen in a Roadtrek.

[gregmchugh]

Originally Posted by booster

Re the AGM battery potential problems.

As Greg points out, the lithium voltages are higher so the AGM won't severely discharge until after the lithiums are all done, which should be very uncommon or impossible. Any troubles with the AGM will likely be from chronic overcharging, as the power sources will be constantly attached to it, and even the lithium battery voltages are higher for much of the range than AGM likes for float. Imagine that poor AGM, that is already full, seeing 5 cycles of full charge voltage off the engine generator, in only a few hours of Voltstart, and then going on a 5 hour drive still charging.

Of course, this is nothing new in RVs, as the battery systems have always been hooked up this way, leaving them vulnerable to overcharging under various conditions, and undercharging during others. It is why you will probably never see a set of RV batteries last anywhere near the rated number of cycles, or more accurately "lifetime total usable amp hours".

I think the article Greg talked about concerning mixed batteries was for stationary power backup, with essentially perpetual float, so probably not a very good indicator of what will happen in a Roadtrek.

So, if the Balmar regulator is set to an AGM battery profile will the AGM be overcharged?

[Davydd]

Originally Posted by cruising7388

No, what I really don't understand is how someone as intelligent as you clearly are, can cavalierly extrapolate your personal modus operandi to the general RV population where technical Brahmins are in the clear minority if not a rarity.

I'm both surprised and delighted that RT has presumably provided me with not one, but two AGM batteries although crawling under the coach, truth to tell, I can find only one.

Your trotting out the KISS principle cracks me up. You waste no words criticizing Roadtrek's less than perfect execution which is fair dinkum. It's well deserved. But when you are faced with the observation that the ARV battery setup has a wart of its own, you're disposed to turn an admittedly minor flaw into a virtue by invoking the KISS principle. Sorry, but that dog ain't gonna hunt. A two hundred thousand dollar coach shouldn't require the owner to keep your finger plastered to a reset switch for 2 - 6 minutes to waken a shut down battery out of its coma.

I get this kind of reply from someone that has to crawl under their B to figure out what they have and still is not sure?

When I quoted two batteries I was referring to the ETrek Sprinter I saw last Spring and here it is. Thanks for you snide comment.

[gregmchugh]

Originally Posted by Davydd

I guess you didn't understand it has never happened in nearly 2 years and 44,000 miles of RV travel other than my deliberate curiosity testing. There is no need for backup AGM batteries to save a few minutes if it ever did happen. Advanced RV provides owners with much more battery status information as I described beyond idiot lights that any ARV owner can understand. Sometimes the KISS principle applies and adding two AGM batteries is not KISS.

I noticed a couple of reports of ARV premature battery bank shutdowns on the Facebook group. When restarted, the bank was still at a high state of charge.

Has this ever happened to you?

I wonder if the shutdowns might have been due to cell temperatures out of limits or some other protected condition. I suppose the computer connection to the system you mentioned might have a log file with info on the reason for the shutdown.

[booster]

Originally Posted by gregmchugh

So, if the Balmar regulator is set to an AGM battery profile will the AGM be overcharged?

In theory, all the charging sources should be in float for a full battery, but many don't do that. Add to that the fact that at the 12.8 volts that a full AGM is at, the lithiums would need a full charge. In the case of the Balmar, it will initiate a charge cycle every time it is turned on. If the AGM were just sitting there by itself, full, with the voltage above what the Balmar considers full, it would likely go to float directly (with the possible issue of locking in absorption if there is not a 4 amp load seen). With the Roadtrek setup, the lithiums are going to be very close to that threshold, so they must be doing something in the settings to get the Balmar to go to charge voltage, or maybe just the high current to lithiums will do it. Either way, at 12.8v, which the chart says is 10% SOC of the lithiums, the AGM is still full, so when the Balmar goes to charge voltage, the AGM will see it while full, for the full charge cycle.

I would think all the other charge sources would also have similar confusions as the lithiums will need to charge badly at 12.8, but the AGM is full. The common charges and solar controllers run on algorithms to guess what is needed, so if they are using them I doubt they are could accurately interpret high current at a voltage that should indicate at full battery.

Some charging sources do run a charge cycle every time they are activated. Progresssive Dynamics is one of them, and will run 4 hours at absorption every time they are turned on and go into absorption (I am not sure if any of them go directly to float if they see high enough voltage).

Since we don't really know how Roadtrek is doing it, it is very hard to guess, but I don't see how the standard charging profiles would work if the check voltage before going to full charge, unless they can change the threshold up to over 14+ volts, as they would never get to full charge voltage.

They may be using charging sources that allow fixed voltage charging, all the time, or that do a full charge every cycle, regardless of voltage at starting, and turning off the lithiums with the BMS. This is the way most lithium setups like to work, it appears, but it would be hard on the AGM battery. Of course, Roadtreks could be in float voltage most of the time, even when they shouldn't be, if they are using normal AGM profiles as was mentioned. Not ideal for sure, but if they had a high float voltage they might get by.

Without actually having the meters on a Roadtrek under some varying conditions, we are only guessing, and based on all the surprises we have seen, it could be anything.

[gregmchugh]

Originally Posted by booster

Without actually having the meters on a Roadtrek under some varying conditions, we are only guessing, and based on all the surprises we have seen, it could be anything.

It could be anything is the truth...

Roadtrek has stated that the inverter and solar controller are in some way custom built for Roadtrek so the actual charge profiles could be anything. I expect the same may apply to the Balmar regulator in terms of its charge profile. Maybe some geek owner will put a recording voltmeter on the system and get actual data.

Also, I would think that if the charge strategy results in charging the Ecotreks to less than full on occasion, but not too much less, that is not a significant issue either, if the AGM battery gets a longer life.

In the end, it may be what you suggested, shortened life for the AGM battery but that is nothing new since it happens regularly on most RVs for various reasons...

[markopolo]

Continual charging of LiFePO4 does not look to be a recommended practice. Continual charging (float or other) above 13.4V is not a recommended practice for AGM's.

Charging an already fully charged AGM while driving could shorten its life as Booster pointed out.

When on campground or solar power, ideally the setup would allow the LiFePO4 to disconnect from charging after becoming fully charged. Let them drop to a preset SOC level before charging them again. The LiFePO4 could still supply DC power in an inverter/charger setup. A converter setup would supply DC loads on campground power. At the same time, you'd want to float charge the AGM.

Take a look at this image combining LiFePO4 and AGM OCV charts to visualize the differences:

parallel LiFePO4 and AGM OCV.jpg

You'd have to make sure the LiFePO4 and AGM batteries are not connected in long term unplugged storage if under covered or shaded storage or risk returning to a depleted LiFePO4.

[avanti]

Originally Posted by gregmchugh

I expect the same may apply to the Balmar regulator in terms of its charge profile. Maybe some geek owner will put a recording voltmeter on the system and get actual data.

It is easy to read out the settings of the Balmar using a magnet and the little display. Well, not easy, but only because it all goes past so fast. It keeps repeating, though. Best to video tape a cycle.

[gregmchugh]

Originally Posted by markopolo

Continual charging of LiFePO4 does not look to be a recommended practice. Continual charging (float or other) above 13.4V is not a recommended practice for AGM's.

Charging an already fully charged AGM while driving could shorten its life as Booster pointed out.

When on campground or solar power, ideally the setup would allow the LiFePO4 to disconnect from charging after becoming fully charged. Let them drop to a preset SOC level before charging them again. The LiFePO4 could still supply DC power in an inverter/charger setup. A converter setup would supply DC loads on campground power. At the same time, you'd want to float charge the AGM.

Take a look at this image combining LiFePO4 and AGM OCV charts to visualize the differences:

Attachment 3698

You'd have to make sure the LiFePO4 and AGM batteries are not connected in long term unplugged storage if under covered or shaded storage or risk returning to a depleted LiFePO4.

While I don't recall any owner reports confirming it, any of the Ecotrek modules should disconnect the charge terminal from the cells when full charge is obtained and reconnect later after some level of discharge as you suggested to resume charging. The load terminal should remain connected. The only question is what happens on shore power since the battery charger in the inverter is connected to the load terminal. I suppose there could be a way to insure that the lithium cells do not overcharge in that case but I don't know the mechanism.

With the van sitting with the Ecotreks all offline, the AGM is not connected to the lithium cells but does remain connected to the solar controller and the underhood generator. Roadtrek does suggest having the Ecotreks offline and at a specified storage state of charge voltage for long term storage.

Roadtrek is preparing a Winter Usage guide to define storage and operational guidance in cold temperatures. Thus should cover the operation of battery heaters and specify a minimum temperature for storage of an unpowered van.

[Davydd]

Originally Posted by gregmchugh

I noticed a couple of reports of ARV premature battery bank shutdowns on the Facebook group. When restarted, the bank was still at a high state of charge.

Has this ever happened to you?

I wonder if the shutdowns might have been due to cell temperatures out of limits or some other protected condition. I suppose the computer connection to the system you mentioned might have a log file with info on the reason for the shutdown.

Greg,

I've read that. They could have been computer glitches or some other problems I have not encountered. I've had my share but always recovered. I had one shut down from cold temperature when I first got my ARV and that was due to misreading a switch and I had the battery heaters shut off and didn't realize it. When I figured it out I could have prevented it but I let it happen because my experimental mode kicked in and I wanted to see if the shutdown and recovery worked. It did. From that experience ARV has since made that mistake more failsafe with additional positive feedback redundancy on the Silverleaf screen as I described earlier. That is also now how I can monitor when the battery heating pads come on and how long they might stay on at given temperatures.

My only other time was deliberate to drive down the SOC without Autogen activated and everything worked as described in ARV's manual including that need to hold down a toggle switch until a readable 1% SOC back to 21% brought power back on. I'll take that might never happen little inconvenience over carrying an AGM battery with its own issues.

I also had a moisture problem in heavy sudden rains that shorted out the battery electronic sensor connections. In that case the batteries came back online automatically with no need to hold the toggle switch when the connections dried out. As it turned out a sudden pressure differential was sucking water into the supposedly sealed battery case. That was solved by a dime-sized Gortex valve on the case. I have an insulated fiberglass case. ARV, I noticed, is now building insulated stainless steel boxes as of last spring but I have no knowledge of what they are now doing beyond that. The stainless steel boxes eliminated all the heavy iron mounting cage that was protecting my battery case. The skid plate protector is still there. I had the very first build using Elite Power Solutions GBS batteries. I was a big boy and knew what I was getting in to.

This second year everything has been bullet proof so far though I have had Balmar regulator temperature sensor issues, Nation alternator issues (and why I enthusiastically upgraded to that Delco), macerator failure and a VB Air Suspension bag leak. Advanced RV has taken care of all that immediately either at their shop, a field visit, or in my case Mercedes Benz dealers in Scottsdale, AZ and Shreveport, LA. I took care of my own Sprinter problem of the power steering line freakingly coming off at the Mercedes Benz dealer in Littleton, CO. All in all, those three visits to MB dealers cost me about 6 hours of total wait time at the dealers. I have a good impression of MB service.

If the SOC is over 20% on a shut down the restart toggle hold is almost instantaneous so you can deliberately shut down your battery bank for storage and not have that hold down agony. I understand as you surmised ARV can plug in a computer and read a log of what had happened to their electronics. They had done that when I was in their shop.

[gregmchugh]

Originally Posted by avanti

It is easy to read out the settings of the Balmar using a magnet and the little display. Well, not easy, but only because it all goes past so fast. It keeps repeating, though. Best to video tape a cycle.

I don't recall if Roadtrek ever stated that they install a custom version of the Balmar but they could possibly be doing that...