Lithium 80% DOD rule

[gregmchugh]

Since the cat is out is the bag after it was mentioned on the Roadtreking group, the latest issue found is that at very hot temperatures, the Roadtrek underhood generator, at idle standing still with no airflow to cool it, does not have enough power output to handle the high cycle times for the roof air conditioning and the batteries will be discharging. Given enough time the Ecotreks will shutdown at the 80% discharge point and you have no air conditioning. Roadtrek is aware of the issue and is looking at a fix but the only possible fixes would seem to be some airflow to possibly cool the alternator or to upgrade the aux alternator to one that can provide more power at idle in hot weather. They have always suggested running the chassis air conditioning when running the roof air from the engine generator to get maximum cooling, not sure if the issues still occur in that case.

[booster]

Originally Posted by gregmchugh

Since the cat is out is the bag after it was mentioned on the Roadtreking group, the latest issue found is that at very hot temperatures, the Roadtrek underhood generator, at idle standing still with no airflow to cool it, does not have enough power output to handle the high cycle times for the roof air conditioning and the batteries will be discharging. Given enough time the Ecotreks will shutdown at the 80% discharge point and you have no air conditioning. Roadtrek is aware of the issue and is looking at a fix but the only possible fixes would seem to be some airflow to possibly cool the alternator or to upgrade the aux alternator to one that can provide more power at idle in hot weather. They have always suggested running the chassis air conditioning when running the roof air from the engine generator to get maximum cooling, not sure if the issues still occur in that case.

That would indicate that the engine generator is turning itself down a long ways if it can't handle 100 amps or so, at 50% engine running. It makes sense, as Avanti saw about 180 amps average on his setup, and to break even on 50% running and 100 amp load, you would need to average 200 amps.

ARV had air ducts and who knows how much else trying to keep the original setup cool, so I would expect they had similar issues, although I don't know if it was ever stated if it was keeping up with use, or failures that made them change.

Is this on all models, or just ones that don't get as much air available? They are going to have a hard time reducing the temp around the alternator much in a stationary vehicle that is running at near 200 degrees and blowing hot radiator air through the whole area.

[mojoman]

Sounds like symptoms of inadequate insulation and dark color paint jobs. I'm able to cool the entire van with the dash AC while sitting in traffic in the very hot conditions.

[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.

[gregmchugh]

Originally Posted by booster

That would indicate that the engine generator is turning itself down a long ways if it can't handle 100 amps or so, at 50% engine running. It makes sense, as Avanti saw about 180 amps average on his setup, and to break even on 50% running and 100 amp load, you would need to average 200 amps.

ARV had air ducts and who knows how much else trying to keep the original setup cool, so I would expect they had similar issues, although I don't know if it was ever stated if it was keeping up with use, or failures that made them change.

Is this on all models, or just ones that don't get as much air available? They are going to have a hard time reducing the temp around the alternator much in a stationary vehicle that is running at near 200 degrees and blowing hot radiator air through the whole area.

Not sure from what I have seen so far if it is isolated to specific models or not. It has been reported on two Chevy models as I recall. With Voltstart active you still get some extension in air conditioner runtime but not what you might expect. It also occurs when you are running the engine continuously to use the roof air which means it is less capable then the Onan it replaced. I think you are right that it is going to be difficult to cool the aux alternator and they will have to upgrade it, probably not to the big Delco used by ARV but something between the two that will fit in the Chevies and Promasters in addition to the Sprinter..

[Davydd]

Originally Posted by gregmchugh

Since the cat is out is the bag after it was mentioned on the Roadtreking group, the latest issue found is that at very hot temperatures, the Roadtrek underhood generator, at idle standing still with no airflow to cool it, does not have enough power output to handle the high cycle times for the roof air conditioning and the batteries will be discharging. Given enough time the Ecotreks will shutdown at the 80% discharge point and you have no air conditioning. Roadtrek is aware of the issue and is looking at a fix but the only possible fixes would seem to be some airflow to possibly cool the alternator or to upgrade the aux alternator to one that can provide more power at idle in hot weather. They have always suggested running the chassis air conditioning when running the roof air from the engine generator to get maximum cooling, not sure if the issues still occur in that case.

It is definitely an air conditioning issue and something I had not been concerned with much at all. I thought I alluded to this way back that Advanced RV air conditioner users found this out and was the major reason ARV went to the Delco alternator as their standard now. ARV called it a death spiral. ARV from day one with the Nations dual alternator had ducted forced air directly on the alternator. That wasn't enough they say. When I upgraded to Delco they tore out the ducts and fan and determined it wasn't needed.

The high idle option increases the output significantly. With my Delco alternator it is almost double over regular idle. I never thought to check that with my Nations. I can see where regular idle with the more powerful Delco could barely keep up with air conditioning demand and all other electrical demand when the alternator was still cool. Still, with the Nations alternator at high idle, which I understand Roadtrek hasn't been using, was not enough from ARV's viewpoint.

Upgraded alternator? I'm not an expert on what might be available. I know ARV struggled with their decision for more than a year trying to figure out how to control cost as the Delco was once way more expensive. If you saw that ARV video you know the Delco is about double in size to the Nations. It still fits the Sprinter but ARV could not use the standard MB mounting brackets. They had to design their own custom brackets. In looking at the Nations Promaster installation it appears the Delco would be too big.

A lot of learning curves going on with this new technology. Personally I don't mind. I am at an age where doing the wait for the shake out is time wasted. Of course, everything will be better next year.

[mojoman]

Sounds like the same situation I ran into when I was selling RV's, a few select individuals found the the bathroom entirely too small, the simplest solution was indroducing salads to their diet.

Has anyone used a infrared thermometer on their unit to see where most the heat is gained? I'm constantly scanning in extreme conditions and slowly improving my unit's R factor and that has significantly lessen the demand for heat or cooling.

[Davydd]

I know the Roadtreks and most all the dealer delivered RV brands are not that well insulated. In speaking for Advanced RVs and the air conditioning results I mentioned, the Advanced RV is insulated first with 100% coverage of the entire inside, floor, walls, wheel wells, doors, ceiling and cab area with Hushmat and 2" of Thinsulate is installed. They also provide insulated curtains, window covers and even a snap on insulated ceiling fan cover. The issue is not lack of insulation for alternator performance.

[mojoman]

A infrared thermometer might enlighten you on insulation performance of your unit, but that type of behavior involves science rather than faith.

[gregmchugh]

Originally Posted by mojoman

Sounds like the same situation I ran into when I was selling RV's, a few select individuals found the the bathroom entirely too small, the simplest solution was indroducing salads to their diet.

Has anyone used a infrared thermometer on their unit to see where most the heat is gained? I'm constantly scanning in extreme conditions and slowly improving my unit's R factor and that has significantly lessen the demand for heat or cooling.

Assessing the Insulation in our RV with an IR Camera

[markopolo]

Originally Posted by gregmchugh

Since the cat is out is the bag after it was mentioned on the Roadtreking group, the latest issue found is that at very hot temperatures, the Roadtrek underhood generator, at idle standing still with no airflow to cool it, does not have enough power output to handle the high cycle times for the roof air conditioning and the batteries will be discharging. Given enough time the Ecotreks will shutdown at the 80% discharge point and you have no air conditioning. Roadtrek is aware of the issue and is looking at a fix but the only possible fixes would seem to be some airflow to possibly cool the alternator or to upgrade the aux alternator to one that can provide more power at idle in hot weather. They have always suggested running the chassis air conditioning when running the roof air from the engine generator to get maximum cooling, not sure if the issues still occur in that case.

Can you provide a link to the discussion? It would be interesting to follow Erwin Hymer Group's progress with this.

You mention a shutdown at 80%. If 80% DOD triggers an LVD (low voltage disconnect) then what % DOD would trigger voltstart?

Is there any indication anywhere that the system is aware of SOC as opposed to it all being voltage triggered events?

[gregmchugh]

Originally Posted by markopolo

Can you provide a link to the discussion? It would be interesting to follow Erwin Hymer Group's progress with this.

You mention a shutdown at 80%. If 80% DOD triggers an LVD (low voltage disconnect) then what % DOD would trigger voltstart?

Is there any indication anywhere that the system is aware of SOC as opposed to it all being voltage triggered events?

I am not positive what voltage is used these days for the Voltsart trigger on Ecotrek vans or what DOD this represents. There have been various numbers quoted. The voltage is obviously different on an AGM van. As the name says, Voltstart is triggered by a voltage reading...

There could be a SOC measurement inside the Ecotrek module but so far there is no SOC info available outside of the module.

Here is the post on the Roadtreking group on Facebook with the info on the air conditioning issue at the end of the comments...

https://www.facebook.com/groups/road...h=a2F0eg%3D%3D

[booster]

I am starting to think that they need to add one more input to the Voltstart system, and that would be van internal temp off a thermostat. There really isn't any reason that I can think of that you would want to run the van to run the alternator to run the inverter to run the coach AC, if you can just run the van AC when all you want is cool. Put a decent hysteresis on it so the run times/off times are reasonable, and forget the rest for AC, including stressing the alternator, and killing the batteries.

Use the batteries to run the AC when you won't be gone longer than they can run the AC, but other times, use the van AC.

[Davydd]

Originally Posted by mojoman

A infrared thermometer might enlighten you on insulation performance of your unit, but that type of behavior involves science rather than faith.

It's not faith. It is knowledge. I don't need an infrared thermometer as I know pretty much from three different Class Bs in progressively more insulation how they perform in that regard. Our insulation is better than what the Fit RV people installed after market and those infrared pictures they showed. I saw the installation of my insulation as well as others at Advanced RV to know the quality of the installation is about as good as you are going to get in a Class B.

I also know there are diminishing returns with much more insulation as my career as an architect at one time designing passive energy homes I know you reach a point where any more insulation is not going to make any difference considering you need air exchange. I've designed those so called zero energy homes with passive solar. My own home built in 1983 is one that will not go below 50 deg. F. if it is -20 deg. F. outside and heats up during the day with no heat on. Conversely the mass of the house inside the insulation envelope and temperature cycles makes air conditioning unnecessary most of the time. The maximum temperature ever reached inside was 88 deg. when it hit 106 degrees outside in 1988.

I've done infrared studies in researching, testing and trying to maximize insulation for Target Stores in all the various climates, and to do some trouble shooting of built stores.

In a Class B unibody design you will have heat transfer ribs, not as tight at doors and operable windows as you might think, venting, lots of glass, etc. making it really difficult. I suppose you could eliminate windows, add a layer of insulation across the face of the ribs thus reducing your interior dimensions and basically start living in a cave. The Advanced RV Solar Womp did that to survive a week in the August Nevada desert boondocking at Burning Man.

I guess I'll say it again. The alternator and air conditioning discussion brought up will not be solved with insulation.

[mojoman]

How foolish of me, to think that the demand of an air conditioner would affect the demand of the alternator. Silly me.

[Boxster1971]

Originally Posted by gregmchugh

...

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

I've seen that paper. Here are two links to it from different sources. It was presented at a conference in 2005. It is an IEEE paper that you need to be member or buy copy. I suspect it was once made available on open source that is gone now.

IEEE Xplore Document - Behaviour of Systems Mixing Parallel Strings of Lithium-Ion and Lead-Acid Batteries for Telecommunications Applications

https://www.researchgate.net/publica...s_Applications

[markopolo]

Originally Posted by gregmchugh

---------------
Here is the post .................................

Thanks Greg - good info to have. Looking back I see that person also mentioned the issue in July 2016. I don't know what model they have.

This alternator: http://www.nationsstarteralternator....-3.6-270xp.htm

Shows:
Idle Amperage: 180
Hot Idle Amperage @ 200ºF: 165

And this link confirms it: https://www.dcpowerinc.com/high-outp...odel=ProMaster

For example you can expect our 270XP to continually do 160+ amps at idle under the most severe conditions due to the alternator not specifically relying on the internal fans to cool the stator.

400ah of discharged lithium batteries would easily accept the above noted full 160A severe condition output.

Running the A/C could require the same output. You have to either severely limit charging or stop running the A/C (could still be in deficit as the person on FB pointed out). I don't think dropping down to one ecotrek would help as I expect it would happily accept the full 160A alternator output as well. You'd need a battery in the mix to provide a reference voltage for the alternator.

Note: alternator output will decrease over time - they don't last forever.

The 13,500 BTU A/C on my 2013 trailer draws 15A at 120V AC in moderate temperature environments measured with an ammeter. That 1800 watts. If you divided that by 10 to allow for inefficiencies and losses etc. you get 180A DC. All other DC coach loads like a fridge etc. would have to be added to that.

[booster]

It certainly does appear that even the redone claims about AC off batteries and engine generators are somewhat exaggerated and the whole idea may be falling away, unless much higher output when hot generators are used, like ARV has done. Of course the monster they use won't fit many applications, I think, and the cost is extreme.

We may be heading back to conventional generators for AC, or using the van AC instead if you don't want a stand alone generator. Engine generators seem to do well at recharging batteries, though. Hopefully, there will be a new power source of some kind available sometime soon, be it fuel cell, etc, or whatever, as running the van engine just is not a really good solution, even when compared to a conventional generator, if you want air conditioning for long periods in hot weather.

[avanti]

Originally Posted by markopolo

The 13,500 BTU A/C on my 2013 trailer draws 15A at 120V AC in moderate temperature environments measured with an ammeter. That 1800 watts. If you divided that by 10 to allow for inefficiencies and losses etc. you get 180A DC.

Just for the record, I have measured our 11K BTU A/C as consuming 102A DC while running. This is as seen by our Trimetric, so this includes inverter losses.

[markopolo]

The A/C on the trailer is not a power saver type unit They describe it as "the second most powerful air conditioner in the Coleman Mach line". I would have been happier with a PS type that would have given me the chance to run it on my 1500W inverter.

Just looked at a 11k Coleman Power Saver: http://old.rvcomfort.com/rvp/pdf_doc...data_sheet.pdf

Running Watts/Cooling Standard condition 1,025
Running Watts/Cooling Desert condition 1,260