New to RVs and Hopeful Warp Core RoadTrekkers

[WingedRyno]

Originally Posted by gerrym51

Are you sure you have the air conditioner running and not just the fan thats in the air conditioner?.. you need to set the Fan on AU and then set the air conditioner on. Have you practiced sliding the vents on the air conditioner? there are 3. one at each end and the one that lets full blast straight down in the middle. also a fan on the floor helps with spreading the air around

Yes on the sliding vents and yes *I think* on turning the AC on. I do it like the dealer did it. Cycle through mode to make it high and then set the temp to 55F and it shows a little snowflake and then kicks on.

[gerrym51]

Originally Posted by WingedRyno

Yes on the sliding vents and yes *I think* on turning the AC on. I do it like the dealer did it. Cycle through mode to make it high and then set the temp to 55F and it shows a little snowflake and then kicks on.

study this to make sure using correctly.

If you set fan for hi ot always comes on with or without the air conditioner actually being on. the only way to tell-for sure- is to set the FAN for AU

http://bryantrv.com/docs2/docs/opera...313327.037.pdf

[gregmchugh]

I can't think of a way to wire the two solar controllers to do anything other than charge all the online Ecotreks plus the AGM from both solar controllers. The Ecotreks are all connected in parallel on the charge and load terminal sides so any charge and load connections are connected to all the Ecotreks that are online.

[Bud]

"If you set fan for hi ot always comes on with or without the air conditioner actually being on. the only way to tell-for sure- is to set the FAN for AU"

I've been wondering for awhile. How about just sticking one's hand next to the vent? Is it cold? like home, car, etc.?

Bud

[gerrym51]

Originally Posted by Bud

"If you set fan for hi ot always comes on with or without the air conditioner actually being on. the only way to tell-for sure- is to set the FAN for AU"

I've been wondering for awhile. How about just sticking one's hand next to the vent? Is it cold? like home, car, etc.?

Bud

the only Hi or lo on control is for the fan. If you want the fan to just come on when the air conditioner actually comes on the fan must be AU(auto).

when you set control for air conditioner the air conditioner is controlled by what temperature you have the thermostat at.

[WingedRyno]

Originally Posted by gerrym51

study this to make sure using correctly.

If you set fan for hi ot always comes on with or without the air conditioner actually being on. the only way to tell-for sure- is to set the FAN for AU

http://bryantrv.com/docs2/docs/opera...313327.037.pdf

Thank you sir! Will add that to the blog post dedicated to the A/C. It's a softball of a day today with the high at 72 and mostly cloudy and the van is cold from the night of 55 and no heat being used. After 30 minutes of the AC set to 55F and the ambient being about the same, the van is keeping 56F while on shore power.

Will log performance all day today to see how it does. It should be easy for it to stay at 55 given the parameters but even now it's still 1 degree warmer. I suspect that will grow throughout the day.

[booster]

Originally Posted by cruising7388

Your math is spot on but I think you're leveling your volley at the wrong target. The losses involved here are not from a battery with chemistry that invites excessive local discharge. Lithium bstteries seem to have local discharge rates equal to or lower than AGMs. The culprit is the BMS that uses power totally disproportionate to to what should be necessary to fulfill it's mission. The sensors that simply monitor temperature, voltage, power delivery and charge rates involve circuitry operating a signal levels. The remaining viable suspect are the BMS power relays that control the load and charging ports. Redesigned to use bi-stable relays, I don't think the "parasitic" loss would be any higher than it is on the Silverleaf system.

Now whether these lithium batteries provide the return on investment compared to a slug of AGMs that admittedly may have a shorter service life than lithiums, well, that's a different kettle of fish. The RT 6 year non-prorated warranty alleviates some concern with this yet to be determined equation. The incidence of the number and the depth of discharge of these batteries will largely depend on how they are used. Paradoxically,for RT, the larger the battery bank they install, the less likely there will be battery failures within the warranty period but the more likely there will be failures from overworked inverters and altternators.

lithium battery system

is how I stated it, so certainly not inditing all lithium batteries, as it appears to be only Roadtrek that loses anywhere near this much to parasitic.

I was also not saying AGMs were more or less economical in the long or short run, as that is a totally different discussion. I probably should have stated that "wet cell SYSTEMS typically lose that much" to be consistent, and brought it up because lithium systems usually tout their superiority in having very low parasitic losses (at least when stored).

My point on cost is that to get the same real world capacity as other lithium systems, a Roadtrek system has to be larger by at least one module which is not a cheap bandaid to put on, and the customer pays it thinking they are getting more usable capacity than another system of lesser size, which is probably not going to happen. It also totally mucks up their calculations of how long they can run things, as they wouldn't know they need to take of 100ish AH per day for the parasitic, Which is more than 1/2 the usable of a module. If folks are leaving more than one module on at a time to run AC or such, you could need two or more extra modules to compare to other lithium systems. Are the extra modules still in the $3500 range or have the come down?

Until there is a monitoring system that will work on a Roadtrek system and includes parasitic loss, it won't be visible to folks how much power is going to waste, and I am sure that is how Roadtrek would like it to stay.

How many systems do you think Roadtrek would sell if they told you that there is no way to leave the van 2 days unattended, without a charging source, without it going dead before you got back, as any module that is on will have emptied by then just from parasitic. Add a frig at 50ah per day and some other little stuff and it will be sooner than that, even for a 1600ah system. Without an auto switching setup for the modules, that is what you will get. Our 440ah AGM system can easily go over a week with the frig on unattended and uncharged. A plain old vanilla two wet battery system with a compressor frig will go at least 3-4 days.

[WingedRyno]

I'm not sure how much parasitic is lost with these lithium batteries, but at this point it seems pretty academic to me whatever the number is.

I had full batteries when I pulled into Wal-Mart at 1pm. I left the following morning at 7am. I had only one EcoTrek on and powered the F fan the entire time, used the microwave to cook food twice, had my iphone and laptop and cell internet and Google Home powered the whole time and used the water pump from time to time. I never idled the engine or plugged into shore power (obviously).

When I left before the sun came up the next morning, that battery still had more than half of its juice. I'm guessing the sun would have charged it up considerably had I stayed.

This is plenty of power.

[markopolo]

Originally Posted by WingedRyno

................... that battery still had more than half of its juice......................

I'd like to know how you are figuring out the remaining capacity ............. Is it just a total guess?

[markopolo]

SoC curve of an LiFEPO4 cell (4 cells in series in 12V systems)



There's so little voltage difference between 90% SoC & 20% SoC.

[GeorgeRa]

I would assume that a sophisticated system such as the RT one has some kind of shunt based battery monitor to let user know SOC level. As indicated on the previous post chart this type of battery monitor is critical for Li batteries, voltage measurement is practically useless.

[gregmchugh]

Originally Posted by GeorgeRa

I would assume that a sophisticated system such as the RT one has some kind of shunt based battery monitor to let user know SOC level. As indicated on your chart this type of battery monitor is critical for Li batteries, voltage measurement is practically useless.

RT has stated they will reintroduce the Coach Connect system that does provide state of charge info, maybe based on shunt based measurements inside each Ecotrek but maybe not...

[WingedRyno]

Originally Posted by markopolo

I'd like to know how you are figuring out the remaining capacity ............. Is it just a total guess?

Using this SOC table that I shared here that somebody else made, and which seems to be right in my experience (the 13.6 for confirmed fully charged batteries seems accurate to me).

https://convotrek.blogspot.com/2017/...s-on-heat.html

[booster]

That chart is way, way, different than anything I ever recall seeing for lithium. Most show them staying much flatter in the middle range, kind of like this one that shows (to one decimal) the same voltage at 13.2v from 30 to 70% state of charge. The actual voltage of the flat center, I think can vary a bit based on temp, also.

[markopolo]

The Master Instruments chart shows 20% SoC being 13.08V whereas the chart WingedRyno is using shows 13.1V being 50% SoC.

12.44V on the Master Instruments chart indicates 5% SoC whereas the chart WingedRyno is using assumes 12.4V being 20% SoC.

It appears that the chart WingedRyno is using was someones best effort / best guess but likely not accurate.

Another clue as to the inaccuracy of the chart WingedRyno is using would be that it is unlikely that volstart kicks in at 44% SoC. It's more likely that it would trigger closer to 10% SoC than 44% SoC.

[cruising7388]

Originally Posted by booster

Are the extra modules still in the $3500 range or have they come down?

I think from the outset they have been around $2500 per 200ah module. The 400ah setup is now $4992 and the 800ah version is $8684 so there is some savings in the higher ah units. But it's a little sneaky because their $3913 GU option also includes 2 additional AGM batteries for which they otherwise charge $871if ordered as a discrete option. However, if you select the lithium option, they delete the AGMs from the GU option but provide you no credit for their value.

[booster]

The whole "how much power do I have left" gets pretty complicated for an Ecotrek, kind of like having "reverse Peukert" on steroids .

If you discharge the module very quickly, in an hour for instance, you only lose about 4ah to parasitic. If you discharge the module over 24 hours you lose a whopping 96ah to parasitic. If you put a monitor on, about the only way you could be accurate would be to also have a stopwatch running to know how much to address the monitor reading. The loss in one module in a day is very close to two days use for use, even with the compressor frig (depending on weather). All this assumes a 4ah per hour parasitic per module, which may or may not be correct. Has anyone timed how long it takes to run a module from full to shutoff with no loads on it?

[WingedRyno]

Originally Posted by booster

The whole "how much power do I have left" gets pretty complicated for an Ecotrek, kind of like having "reverse Peukert" on steroids .

If you discharge the module very quickly, in an hour for instance, you only lose about 4ah to parasitic. If you discharge the module over 24 hours you lose a whopping 96ah to parasitic. If you put a monitor on, about the only way you could be accurate would be to also have a stopwatch running to know how much to address the monitor reading. The loss in one module in a day is very close to two days use for use, even with the compressor frig (depending on weather). All this assumes a 4ah per hour parasitic per module, which may or may not be correct. Has anyone timed how long it takes to run a module from full to shutoff with no loads on it?

That would be an interesting test. Turn off the fridge and cover the solar and time it. Should give a pretty good idea of BMS draw.

When I have more time I'll try to find a carport or garage and time it.

[wincrasher]

Some of you give RT credit for more sophistication that they probably deserve. They appear to set charge parameters based on voltage and not SOC. It seems to me that is what they are doing when they had to add the AGM battery to make Voltstart work.

Another thing they probably consider is the issue of needing to periodically reset your amp counter with a shunt based system. I've noticed on occasion you need to do that and it may be beyond the understanding of most of their customers and result in more warranty visits. Most folks seem to understand voltage.

From the testing I've done in my bus, I really don't see much difference between setting charge engagement on SOC or voltage. I don't set it for coming on so that I get the maximum depth of discharge - I suppose if you had a small bank, that might be necessary. Somewhere around 30-40% is fine, as the battery has more than enough capacity that it takes awhile to get down that low as it is. Also, the solar coming in is largely wasted if you are precluding charging until the battery were down to 10-20%.

I also never charge fully - I set it to shut off charging at 13.4 or 90%. That way you are using the middle band of the battery capacity, which reportedly will extend it's life significantly, or at least, prevent degradation.

[cruising7388]

Originally Posted by markopolo

SoC curve of an LiFEPO4 cell (4 cells in series in 12V systems)



There's so little voltage difference between 90% SoC & 20% SoC.

I agree that using voltage as a parameter for measuring SOC is certainly inferior to a shunt derived SOC display and adding 3 digit voltmeter registering 100mv increments is practically useless for measuring a lithium battery SOC. However, the 4 digit meter I have that displays 10mv changes provides sufficient sensitivity to permit a barnyard interpolation of our lithium battery state.