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.

[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]

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 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.

[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?

[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.

[markopolo]

Originally Posted by booster

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.

Re: paragraph 3 - Just a note about the Progressive Dynamics converter/charger in my van. I'd describe what I think happens at start up as a pressure test. If required amps exceed X amount to reach Y voltage then full charge cycle begins. If not then it goes into Normal mode 13.6V. I could test to see if it alternately goes straight into float if different parameters are met. I think I've seen that also.

I would assume lithium and lead acid would have, for lack of a better term, different pressure profiles. My guess is that you'd see more amps at lower voltage with lithium compared to lead acid when charging. The size of some of the lithium battery banks we're seeing guarantees high amp flow.

[eric1514]

Originally Posted by markopolo

Re: paragraph 3 - Just a note about the Progressive Dynamics converter/charger in my van. I'd describe what I think happens at start up as a pressure test. If required amps exceed X amount to reach Y voltage then full charge cycle begins. If not then it goes into Normal mode 13.6V. I could test to see if it alternately goes straight into float if different parameters are met. I think I've seen that also...

Mine will very often start out in Normal mode and not Boost mode but not always. I can verify that with the light on the pendant and the simple voltmeter I have installed. I've never seen it start in Float (13.2v) mode, but using the pendant I will force it into that mode almost every time I park the van along side my house.

[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.

[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 Davydd

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.

Very good, thanks for the info...