ecotrek batteries using 6 internal amps

[Davydd]

Cost effective kind of guys buy Travatos.

[booster]

DC Power has a 370 amp alternator in a standard case now. I wonder how much that would heat cycle, and how much more "net" AH you would actually gain.

I looked a bit closer at Avanti's chart to try to guess some closer numbers for the results. It appears that in the early parts of the heat cycling, he was getting about 170 amps on average, and then something happened to reduce the heat cycle drop and it got closer to 185 amps.

By minute 50, the amperage started to drop, which would indicate the batteries would no longer accept full amps any more, I think. That point was at about 65% SOC which I think will surprise many people. At that point he had put in about 135AH, which is about 30% of his capacity. He started at 35% SOC so a full drawdown to 20% would add another 15% SOC to recover to get to the taper point, so it would be about 75 minutes from 20% SOC. If the output stayed at the about 210 amps it showed cold, that same 20% to 66% would have taken about 60 minutes.

To me, all numbers don't mean much until you put them into the real use patterns of the van. For the 20% to 65% SOC example above, you would save 15 minutes of time to get to the tapering amps point, approximately if it didn't heat cycle. At least for us, that would not really be an issue, as once we are above a 15 minute trip to the trailhead or dump station, adding a few minutes to the drive isn't a problem. Others may feel otherwise. Idling would take a bunch more time.

The other extreme of this, if I am understanding davydd correctly, is that ARV is trying to cover air conditioning in very hot climates off of the batteries. This would require frequent recharge cycles, probably at idle. Aside from the fact that at idle, the engine compartment is going to be very hot, you would also have the lower idle output from the alternator unless you have the high idle setting. At that point, the heat tapering would become an issue, using Avanti's numbers. If you are using 140 amps to run the AC, you would only have 30 amps of battery charging based on the 170 amp hot average. If it stayed at even 200 amps, you would double you battery charge rate, but it would still be a paltry 60 amps and take way too long to charge enough power to run the AC long. If you can get an alternator to charge hot at 300 amps. You would have over 4 times the battery charge rate and put 130 amps into the batteries. Even at that, you are looking at 5 hours to recover 650AH of power, which will only run the AC 5 hours on batteries. Basically, you would need to run the van engine 50% of the time, even with an alternator putting out 300 amps continuous and hot. Personally, I don't see that as a viable option, even if you are OK with extended idle on the Sprinter. A generator would just make much more sense to me.

Bottom line is that I would have to agree that what Avanti has is by far the most cost effective, and in reality not even giving up much more than a tiny usability advantage in real world use. If this is how the Nations alternators were being used in the ARVs, I am not particularly surprised that they had failure and low output. Sitting still, with no air being pushed to the alternator, would make them run very hot for very long periods.

Of much more use to those of us with AGM batteries is not the above charging to the tapering point, but how to handle the charging after that, as the amperage and SOC gains start to drop quickly at that point, and you still have 35% SOC left to get. After two hours, Avanti was only getting about 35 amps. It looks like if he wants to use the engine charger to get to 10-15 amps so the solar could take over, it would take 3-4 hours. At that point, the solar is probably going to need another 4-6 hours to totally top off, which would indicate an early drive start if you want to do a full topoff without shore power.

[Davydd]

Originally Posted by booster

Bottom line is that I would have to agree that what Avanti has is by far the most cost effective, and in reality not even giving up much more than a tiny usability advantage in real world use. If this is how the Nations alternators were being used in the ARVs, I am not particularly surprised that they had failure and low output. Sitting still, with no air being pushed to the alternator, would make them run very hot for very long periods.

Advanced RV puts in fan ducted air directly on the Nations alternator. Avanti didn't do that nor do I think Roadtrek or anyone else had. BTW, the fan and duct were removed from my B when the Delco alternator was installed. It was no longer needed.

My comments were addressed to driving and running the coach air conditioning. Again, armchair all you want but the Nations alternator did not prove capable in that situation. "If this is how the Nations alternators were being used in the ARVs" means what I think it means then it means others are incapable? There were customers who did intend to use it that way in 100 degree plus temperatures and not 90s that proved it necessary for an improvement. Pet owners were pretty demanding. I tend to believe real world results over theoretical calculations. Again, ARV doesn't do things because it can as Avanti suggests, but because it tries to solve problems and satisfy customers. They are not in the business to satisfy dealers first and customers second.

Anyway, you all make a good case for lithium ion batteries with those charge profiles for AGMs.

BTW, one ARV owner did claim 13 hours overnight with air conditioning on the low setting with his 800ah battery bank in 90 degree whether. I can't substantiate that but it was claimed. There had to be a lot of cycling I would imagine. The ARV's are better insulated than any other B I know of. I haven't heard any exact reports about that ARV mostly windowless Solar Womp model other than it lasted the full time at Burning Man last year boondocking.

[avanti]

Originally Posted by Davydd

Again, armchair all you want but the Nations alternator did not prove capable in that situation.

Let's be precise: The system that ARV designed around the Nations alternator did not prove capable in that situation. The evidence does not extend beyond that statement.

I tend to believe real world results over theoretical calculations.

You might want to consider paying attention to both. Theoretical calculations tell us what is possible. Real-world results tell us what has been achieved. The difference between the two is a measure of the skills of the designer.

My point is that if real-world results exceed what the theory says is possible, then shame on the theory. If (as in this case), the the results fall short of theory, shame on the designer.

Again, ARV doesn't do things because it can as Avanti suggests

That is not what I said. I said that ARV does things to the highest specification, cost be damned. As to their motivations for this, I will not speculate.

BTW, one ARV owner did claim 13 hours overnight with air conditioning on the low setting with his 800ah battery bank in 90 degree whether. I can't substantiate that but it was claimed.

This is not impossible.

[cruising7388]

Originally Posted by gregmchugh

i don't recall anyone saying that a central bms would not work well just that it does not fit into roadtrek's decision on the system architecture using modular components...

#78 #211 #213 #214 #215 #232

[booster]

Originally Posted by gregmchugh
i don't recall anyone saying that a central bms would not work well just that it does not fit into roadtrek's decision on the system architecture using modular components...

Originally Posted by cruising7388

#78 #211 #213 #214 #215 #232

I guess I don't understand what you are trying to say. Of those posts, only BBQ's seems to support individual BMS systems. The rest are in support of a central system or at least implying central by stating that there seemed to be missing logic in the way Roadtrek did things. Heck, two of them were your posts, and don't seem to to dis central BMS.

[gregmchugh]

Originally Posted by booster

Originally Posted by gregmchugh
i don't recall anyone saying that a central bms would not work well just that it does not fit into roadtrek's decision on the system architecture using modular components...



I guess I don't understand what you are trying to say. Of those posts, only BBQ's seems to support individual BMS systems. The rest are in support of a central system or at least implying central by stating that there seemed to be missing logic in the way Roadtrek did things. Heck, two of them were your posts, and don't seem to to dis central BMS.

I don't see any significant differences in the two approaches from a battery management point of view, given a good low power design for either approach it seems to be 6 of one, half dozen of the other.

In terms of actual pros and cons for the two system approaches, here are some thoughts off the top of my head...

There are clearly some pros and cons to the two system architectures used by ARV and Roadtrek.

In terms of the parasitic loss of usable energy by the battery management system there is no technical reason that either architecture cannot have a negligible loss of energy from powering the battery management system. The pros and cons of the two basic architectures are not related to the usable power from the lithium cells, both can have essentially equivalent usable power from equivalent lithium cells. The design of the battery management system in the Roadtrek Ecotrek 200 AH module could be modified to reduce the power loss to a negligible level where it is not an issue.

The ARV design is a pretty standard design for an RV lithium battery bank these days, the ARV implementation can be noted for: selection of quality components, robust installation under the van, integration of the battery system status and control into the coach wide display and control system, and the addition of battery heaters to the battery bank. .

The Roadtrek Ecotrek 200 AH module approach is similar in some ways to the drop-in lithium battery designs from Stark and others, the Roadtrek implementation can be noted for: the addition of an auxiliary AGM battery wired in parallel with the Ecotrek modules, the addition of battery heaters inside the drop-in modules, splitting the connections on the module into charge and load terminals with the connection to the battery cells on both terminals likely controlled by relays, and a connector on each module to interface to control switches for each module and possibly an interface to a central controller.

In terms of pros and cons, some that have been noted include:

A pro for the ARV approach of building integrated battery banks with a single battery management system for each AH capacity option is that the size and weight of the battery system are minimized for each AH option.

Only cons that I recall being mentioned for the ARV system design are the lack of a built in facility to bring a cold soaked inactive battery bank up to temperature (may not be a feature needed by a majority of buyers) and the fact that a failure of any of the battery cells will shut down the entire battery bank (this may be a rare enough failure that it can be dismissed as a con).

I don't recall any statements from Roadtrek discussing the reasons for their choice of architecture but I can imagine that the modular approach gives them more flexibility by building and stocking a single modular component that can be produced in volume and configured for the wide variety of vans models they produce. Repairs would seem to be facilitated by the easy swapping of modules vs the work needed to repair an integrated battery bank. The con to this is that there is a weight and size penalty by using multiple modules with internal battery management vs an integrated battery bank with a single battery management system. The fact that the modules are mounted under the van does reduce the size penalty somewhat vs a case where the modules would be located inside the van where space is at a premium.

Pros that have been mentioned for the Roadtrek approach include: the capability to bring cold soaked inactive batteries up to operating temperature using power from the underhood generator and the ability to take a failed module offline and continue operating with the remaining modules online.

The cons mentioned for the Roadtrek system have been extensive here on the forum but I am not going to mention those that are due to the unnecessarily large power loss of the battery management functions (these are fixable). The aux AGM battery is considered by many to be a kludge to resolve a design flaw but it does allow the system to power the battery heaters from the underhood generator so other than the weight and size penalty of the extra battery I am not inclined to list any other cons associated with the AGM battery but I accept that this may be a minority opinion. A major con of the current Roadtrek system is the lack of any useful system status information, the most glaring issue being no information on the state of charge of the batteries. The two control switches associated with each Ecotrek module get very unwieldy as the battery bank grows up to the case where there are 8 pairs of switches for the 1600 amp hour option. I would hope that the reintroduction of the Coach Connect option is taken as an opportunity to get rid of the physical switches and integrate all display and control features (including system status info) into a touch screen display.

That's enough for my thoughts on this for the moment, I expect others will add their thoughts to expand on this attempt to summarize the pros and cons of the two systems...

[cruising7388]

Originally Posted by booster

Originally Posted by gregmchugh
i don't recall anyone saying that a central bms would not work well just that it does not fit into roadtrek's decision on the system architecture using modular components...



I guess I don't understand what you are trying to say. Of those posts, only BBQ's seems to support individual BMS systems. The rest are in support of a central system or at least implying central by stating that there seemed to be missing logic in the way Roadtrek did things. Heck, two of them were your posts, and don't seem to to dis central BMS.

Actually, I much prefer the idea of a central BMS and agree with the suggestion that RT makes their BMS systems native to each battery more for their marketing and production benefit than for any practical benefit that accrues to the customer. I was simply noting that gerry, BBQ and Booster had some reservations regarding a unified BMS.

Now it turns out, that for reasons that RT most likely didn't contemplate, to mitigate power losses to just one battery that presumably will be supported by a solar panel, there is some advantage in being able to shut down some batteries. But I'd be the first to agree that this feture looks less like a well contemplated triumph in design and more like a bandage for a control system that from reports seems to be afflicted with electron hemophilia.

[cruising7388]

Originally Posted by gregmchugh

I don't see any significant differences in the two approaches from a battery management point of view, given a good low power design for either approach it seems to be 6 of one, half dozen of the other.

In terms of actual pros and cons for the two system approaches, here are some thoughts off the top of my head...

There are clearly some pros and cons to the two system architectures used by ARV and Roadtrek.

In terms of the parasitic loss of usable energy by the battery management system there is no technical reason that either architecture cannot have a negligible loss of energy from powering the battery management system. The pros and cons of the two basic architectures are not related to the usable power from the lithium cells, both can have essentially equivalent usable power from equivalent lithium cells. The design of the battery management system in the Roadtrek Ecotrek 200 AH module could be modified to reduce the power loss to a negligible level where it is not an issue.

The ARV design is a pretty standard design for an RV lithium battery bank these days, the ARV implementation can be noted for: selection of quality components, robust installation under the van, integration of the battery system status and control into the coach wide display and control system, and the addition of battery heaters to the battery bank. .

The Roadtrek Ecotrek 200 AH module approach is similar in some ways to the drop-in lithium battery designs from Stark and others, the Roadtrek implementation can be noted for: the addition of an auxiliary AGM battery wired in parallel with the Ecotrek modules, the addition of battery heaters inside the drop-in modules, splitting the connections on the module into charge and load terminals with the connection to the battery cells on both terminals likely controlled by relays, and a connector on each module to interface to control switches for each module and possibly an interface to a central controller.

In terms of pros and cons, some that have been noted include:

A pro for the ARV approach of building integrated battery banks with a single battery management system for each AH capacity option is that the size and weight of the battery system are minimized for each AH option.

Only cons that I recall being mentioned for the ARV system design are the lack of a built in facility to bring a cold soaked inactive battery bank up to temperature (may not be a feature needed by a majority of buyers) and the fact that a failure of any of the battery cells will shut down the entire battery bank (this may be a rare enough failure that it can be dismissed as a con).

I don't recall any statements from Roadtrek discussing the reasons for their choice of architecture but I can imagine that the modular approach gives them more flexibility by building and stocking a single modular component that can be produced in volume and configured for the wide variety of vans models they produce. Repairs would seem to be facilitated by the easy swapping of modules vs the work needed to repair an integrated battery bank. The con to this is that there is a weight and size penalty by using multiple modules with internal battery management vs an integrated battery bank with a single battery management system. The fact that the modules are mounted under the van does reduce the size penalty somewhat vs a case where the modules would be located inside the van where space is at a premium.

Pros that have been mentioned for the Roadtrek approach include: the capability to bring cold soaked inactive batteries up to operating temperature using power from the underhood generator and the ability to take a failed module offline and continue operating with the remaining modules online.

The cons mentioned for the Roadtrek system have been extensive here on the forum but I am not going to mention those that are due to the unnecessarily large power loss of the battery management functions (these are fixable). The aux AGM battery is considered by many to be a kludge to resolve a design flaw but it does allow the system to power the battery heaters from the underhood generator so other than the weight and size penalty of the extra battery I am not inclined to list any other cons associated with the AGM battery but I accept that this may be a minority opinion. A major con of the current Roadtrek system is the lack of any useful system status information, the most glaring issue being no information on the state of charge of the batteries. The two control switches associated with each Ecotrek module get very unwieldy as the battery bank grows up to the case where there are 8 pairs of switches for the 1600 amp hour option. I would hope that the reintroduction of the Coach Connect option is taken as an opportunity to get rid of the physical switches and integrate all display and control features (including system status info) into a touch screen display.

That's enough for my thoughts on this for the moment, I expect others will add their thoughts to expand on this attempt to summarize the pros and cons of the two systems...

Great post. Thank you!

I have it on pretty good authority that currently RT now includes digital voltage metering of coach battery state on their coaches but don't know if this applies to all their production or just lithium equipped units. But for lithiums, unless the meter displays millivolts, I think it's pretty much a colorful ornament. What this system needs is shunt derived Voltage, amperage, SOC metering, but even with this support, unless the operator recalibrates that meter every time batteries are put on or taken off line, it would provide correct voltage and amperage delivery but state of charge and remaining capacity information would be incorrect.

[gregmchugh]

Not easy to get accurate state of charge with the RT system but not impossible. Shunt in each Ecotrek module with network communication to a central display system. Fix the power drain problem and you can keep all modules online all the time to report their status.

[Davydd]

Greg, You gave a pretty good overview. gerryM51 has said a couple of times that Roadtrek's modular system was more for their design efficiency across models. To me that is build concern first, dealers second and customer third. I'm not sure if Coach Connect is like or similar to Silverleaf, but all it does is make things simpler to operate. Behind my Silverleaf monitor is a panel that can be removed and a ton of hidden away crammed electronics modules. I don't know if you actually eliminate much.

I have one complete build of a battery bank in an insulated fiberglass box. When I was last at ARV I noticed they were modularizing their battery banks in two side by side insulated stainless steel boxes capable of holding 400ah each but still one BMS I think. They have eliminated the extensive steel angle iron protection I have but the thick aluminum skid plate protection is still the same. Heck, who knows what they are doing there today since I haven't been there since May and Mike Neundorfer has been on long distance trips in his Bs. They don't wait for model years. The good thing is they will readily upgrade your van if it is feasible to correct or improve anything they've learned. Many upgrades are totally gratis, others at cost.

I'm not concerned about cold weather from my two winter experience now in Minnesota and certainly would not want two AGM batteries as a solution. Most of the United States would never encounter a problem. Minnesota is an extreme and only during cold winter storage and never on the road. ARV has put in built in protection and there are simple solutions for getting underway in the winter. To me it is less of a problem one has to go through to de-winterize a B when leaving cold weather and needing to get to warm weather to do so.

I am still a bit concerned about the -4F condition for cold storage ARV has alluded to. So far I am finding that as an operating temperature for some battery manufacturers and -22F as another. If I stay plugged into shore power to power the heating pads that is not a problem. ARV prevents charging batteries under a conservative 41F. I figured out you can heat batteries externally rather easily after I dumbly and mistakenly had the heating pads turned off (since fixed with a gratis upgrade.) At least I found out the fail safe worked.

[booster]

I agree with Greg, there is is absolutely no reason either a central, or module approach can't work well. Any decent system integrator could do a system in their sleep, IMO.

If Roadtrek does go to a "digital" voltage reading, it is just a different way of displaying information that doesn't tell you anything useful and only marginally better than the idiot lights. As was mentioned many times, a shunt based system that measures actual SOC (pick your parameters for that, though) is a necessity if you want to be anywhere near accurate. If it is just a monitoring system though, all it will do is show you how bad the control system is taking care of business. The charging, discharging, cutoffs, etc all need to be tied together in the control system, including the SOC information.

Most of this is not rocket science. A $200 solar controller system can do almost all of it. A Victron monitor has a relay output that can be programmed off of SOC. The list goes on.

If folks can put together a better controlled, more reliable, lithium system, at home, out of off the shelf parts (which they have), than Roadtrek can with all their proprietary stuff, there is really something wrong.

[Jostalli]

Originally Posted by Davydd

I'm not concerned about cold weather from my two winter experience now in Minnesota and certainly would not want two AGM batteries as a solution.

I would be more concerned with batteries getting too hot. We just returned from a 5500 mile trip where temps were over 90 degrees most of the time. The last two days were 110-118 degrees. Our 640AH LiFePO4 batteries are inside so no issues.

[gregmchugh]

From the owners point of view are there any significant differences between the two architectures?

Assuming the design issues of the current Roadtrek system are fixed and ARV found that buyers wanted the capability to warm up a cold soaked van and implemented that feature then I can only think of only one difference an owner would find between two identical vans with the two different architectures. The cargo carrying capacity would be reduced with the Roadtrek architecture but how much difference is unknown without some details of the system weights. The batteries are under the van so no difference in interior living or storage space.

What other differences would be apparent to the owner?

[booster]

Originally Posted by gregmchugh

From the owners point of view are there any significant differences between the two architectures?

Assuming the design issues of the current Roadtrek system are fixed and ARV found that buyers wanted the capability to warm up a cold soaked van and implemented that feature then I can only think of only one difference an owner would find between two identical vans with the two different architectures. The cargo carrying capacity would be reduced with the Roadtrek architecture but how much difference is unknown without some details of the system weights. The batteries are under the van so no difference in interior living or storage space.

What other differences would be apparent to the owner?

I think if there were any obvious differences, it would be due to setup parameters primarily, such as what are the charge and discharge cutoff points, which would determine usable capacity. Beyond that, if both systems are of high quality, they should be basically invisible, except for monitoring.

[Davydd]

Originally Posted by Jostalli

I would be more concerned with batteries getting too hot. We just returned from a 5500 mile trip where temps were over 90 degrees most of the time. The last two days were 110-118 degrees. Our 640AH LiFePO4 batteries are inside so no issues.

I'm not concerned about hot weather either. For one, I would never plan a trip where I encounter extreme temperatures and living in the north it is not much of an issue. As for inside, that would mean you would have to always have temperature control on because a B will get much hotter unattended inside than having the batteries underneath in a box. Technomadia ran into this problem initially with an uncontrolled inside "oven." Conversely, in the winter it would be stupid to heat the inside of a coach just for batteries when small heating pads in an enclosed insulated box work more efficiently.

Also there is a great sacrifice in storage space with batteries inside. My 800ah battery bank dimensions are about 20" x 22" x 10". That's over 2-1/2 cubic feet not counting buss bars and wiring. When you have a large ah capacity you most certainly need a large capacity inverter to take advantage of it. The inverter alone eats up a lot of inside storage space.

Is cooling necessary? The most conservative information I've seen says operating temperatures should not exceed 113 degrees in operation. Battery manufacturers generally say a maximum of about 140-149 degrees in storage. It will never get that hot stored underneath. If you design a car like Tesla that has to be sold to operate year round everywhere I can see the precaution. If you live in the south it might be a concern. As I said, it will not be a problem in Minnesota though I have seen the inside of my B as high as about 120 degrees unattended in Minnesota. Inside is an oven with all the windows and the sun.

Yes, I am concerned about the low unattended storage temperature. If it is -22F (-30C) I am not too worried. Thanks climate change. If -4F (-20C) it would be a concern for me.

[mojoman]

I assure you, living in the west, the undercarriage will experience very hot temperatures from the heat radiating from the road which is allot hotter than ambient, sometimes double the temps. Thats why I installed mine inside and added undercarriage insulation.

[Davydd]

Originally Posted by mojoman

I assure you, living in the west, the undercarriage will experience very hot temperatures from the heat radiating from the road which is allot hotter than ambient, sometimes double the temps. Thats why I installed mine inside and added undercarriage insulation.

I know you said that before and I have tested. You're wrong. Park your van. Close up your van. Stick a thermometer inside and one under your van right in the center. Then tell me again what you said.

[mojoman]

Of course I'm wrong, I live in California!

[cruising7388]

Originally Posted by booster

DC Power has a 370 amp alternator in a standard case now. I wonder how much that would heat cycle, and how much more "net" AH you would actually gain.

The answer doesn't seem easily arrived at.

DC Power claims only a 10% reduction for running hot which is pretty good.

However, if their figures are correct, the real world AH capacity available depends on whether or not it is run at speed or idle. Compared with their 270 amp unit, the 370 delivers a lot more suds, (330A v. 250A both hot) at road speed but at idle speeds, the output advantage almost disappears (190A v. 180A) which constitutes a 50% idle hot derate for the 370A unit whereas the 270A unit derates about 33%.

Nations has an interesting comparison between their models where some frames have a higher power output than others but then notes that the higher power frame has a hot derating of 30% compared to the lower power model that only has a 15% derating, essentially eliminating the benefit of the higher power unit under hot conditions.

What is the derate % for the Delco 330 idling hot?