Ecotrek battery knowledge base

[markopolo]

There's a collection of interesting Ecotrek battery related documents here: http://home.roadtreking.ca/Manuals

The schematic that shows the AGM battery in parallel with the charge side of the lithium battery should be helpful to folks trying to understand the system.

Image: AGM in parallel to Ecotrek charge side.JPG

PDF: http://home.roadtreking.ca/Manuals/F...cotrekVans.pdf

[markopolo]

Possible errors in some docs? The relay action for the OUTSIDE VOLTAGE OVUV parameters seems to be reversed (Lithium Battery Guides) ..... I'd assume that you'd want the Charge Relay to open if voltage is 15.2V and the Discharge Relay to open if voltage is 11.5V.

possible errors.JPG

[cruising7388]

Originally Posted by markopolo

There's a collection of interesting Ecotrek battery related documents here: http://home.roadtreking.ca/Manuals

The schematic that shows the AGM battery in parallel with the charge side of the lithium battery should be helpful to folks trying to understand the system.

Image: Attachment 10773

PDF: http://home.roadtreking.ca/Manuals/F...cotrekVans.pdf

When the vehicle is at rest, If the lithium charge port(s) go open while the inverter is on and supplying power to 120V loads, won't the inverter now see the AGM as its input source and discharge it until its terminal voltage drops to the inverter low voltage input shutdown trigger voltage?

[markopolo]

As shown in the schematic, yes. There nothing to stop that from happening in the drawing.

That AGM is said to be critical to be able to turn the lithium modules on and supply a voltage reference for the Balmar etc.

https://www.classbforum.com/forums/f...tml#post111637

Edited: discharge/charge separated

[cruising7388]

Originally Posted by markopolo

As shown in the schematic, yes. There nothing to stop that from happening in the drawing.

That AGM is said to be critical to be able to turn the lithium modules on and supply a voltage reference for the Balmar etc.

https://www.classbforum.com/forums/f...tml#post111637

Edited: discharge/charge separated

Early Etreks had the battery charger, solar controller and alternator directed to the lithium battery discharge ports. When it was reported that the battery charger could overcharge the batteries. RT changed the connection point to the charge ports.

Yes, if the lithium charge port opens, without the AGM support, the alternator would not see any load and the Balmar regulator would presumably shut the alternator down. So the common AGM support is indispensable.

But this results in a problem. The inverter DC input trip is typically 10V which is not consequential for the lithium batteries since their BLMs will shut them down in the whereabouts of 12 volts. The AGM has no protective circuit and will be sucked down to the inverter 10 volt trip voltage with some consequences to it's capacity and longevity. At least that's what it looks like on paper.

[markopolo]

Two more links:

https://www.classbforum.com/forums/f...-diy-8976.html

https://sites.google.com/view/suiet-...component-data

It seems to me that just about everything about ecotrek batteries system is covered by the two links to outside sites and the two forum topic links posted so far.

The large contactors appear to be Albright or Curtis or a clone of them based on the diamond shaped top and body style.. I looked at an Albright spec sheet for a contactor and the power consumption is 21 watts. There are two of those in each case........ plus 3 or 4 automotive type relays, a BMS and a couple of other modules.........

You can see why the "2018.10.15 Lithiums dead - reset procedure and checks.pdf" ( https://www.classbforum.com/forums/a...3&d=1594391588 ) states 5A to 10A per hour drain.

Quote from the PDF:

In addition, when turned on, even if there are no lights on in the coach or anything running on battery, the lithium modules will have an inherent self-discharge due to the internal relays and electronics of between 5 and 10 Amps per hour that will continue to drain them(Battery Management System). While the solar may be able to keep up with this during the day(depending on variables), at night they continue to discharge. When the modules are turned off, the draw is gone.(Turned off at their EcoTrek switch)

5A x 24 hours = 120Ah per day drain
10A x 24 hours = 240Ah per day drain

If that pdf is correct then a module can only last a day but probably not two days due to self-consumption. Solar input will extend that time by a bit at approx 30Ah per 100W solar per day.

By comparison, drop-in type lithium batteries will last many months on standby.

Please correct if any of the above is wrong.

[Davydd]

I don't understand anything about the Ecotrek lithium battery system from the extraordinary self discharging rate to needing a standby AGM battery online in the system. Is any other Class B upfitter saddled with this in their lithium battery systems?

I know ARV's three different offerings of Elite Power Solutions (build up block modules), Lithiumwerks Valence (drop in modules) and the 48v Volta systems aren't.

[markopolo]

I'm not aware of anything similar out there.

My guess is that they probably would have gone with 400Ah modules had the issues been better understood at inception and not multiple 200Ah modules causing a multiplication of the parasitic losses. That + the high C-rate usage if using only one 200Ah makes a 400Ah module seem much better. I kind of remember that single 200Ah module equipped coaches were available at some point but not offered later on. Someone could correct that if wrong.

Here's an H and L1 photo. Sorry the image quality isn't better.

ecotrek H L1.jpg

Note the additional small gauge wires to the lithium cell terminals and the solid conductor bars instead of heavy gauge wire.

There a report of wiring coming loose here: https://www.classbforum.com/forums/f...tml#post120203

It's not clear from the photos I've seen as to how well the cells are secured in the case. I can't see if the cells are strapped together. There appears to be a HDPE hold down piece on one side. No insulation is visible. I'd guess that micro movements, thermal cycling, vibration etc. can have an effect on fasteners and there are a lot of fasteners in the case.

Photos spread throughout this topic: https://www.classbforum.com/forums/f...-diy-8976.html

For out of warranty, advanced DIYers, getting in there and checking the fasteners might be an off-season project at some point.

[cruising7388]

Originally Posted by markopolo

As shown in the schematic, yes. There nothing to stop that from happening in the drawing.

That AGM is said to be critical to be able to turn the lithium modules on and supply a voltage reference for the Balmar etc.

https://www.classbforum.com/forums/f...tml#post111637

Edited: discharge/charge separated

While the AGM is provided to enable the lithium battery BLM to effect a reset, as indicated on the diagram, it is in parallel with the lithium batteries and it's terminal voltage will mirror the lithium battery voltage. I determined by experiment that the RT BLM shuts down the lithiums at approximately 11.95V.

At 11.95V, the AGM SOC is about 40% which isn't significantly detrimental to this battery. However, the wrinkle is that when the lithiums shut down, the inverter, if on, now sees the AGM as its power source and will continue to discharge the AGM until its terminal voltage declines to the shut down point of the inverter which is 10.5 volts. At 10.5 volts, the AGM SOC = ZERO.

[cruising7388]

Originally Posted by markopolo

I'm not aware of anything similar out there.

My guess is that they probably would have gone with 400Ah modules had the issues been better understood at inception and not multiple 200Ah modules causing a multiplication of the parasitic losses. That + the high C-rate usage if using only one 200Ah makes a 400Ah module seem much better. I kind of remember that single 200Ah module equipped coaches were available at some point but not offered later on. Someone could correct that if wrong.

Here's an H and L1 photo. Sorry the image quality isn't better.

Attachment 10781

Note the additional small gauge wires to the lithium cell terminals and the solid conductor bars instead of heavy gauge wire.

There a report of wiring coming loose here: https://www.classbforum.com/forums/f...tml#post120203

It's not clear from the photos I've seen as to how well the cells are secured in the case. I can't see if the cells are strapped together. There appears to be a HDPE hold down piece on one side. No insulation is visible. I'd guess that micro movements, thermal cycling, vibration etc. can have an effect on fasteners and there are a lot of fasteners in the case.

Photos spread throughout this topic: https://www.classbforum.com/forums/f...-diy-8976.html

For out of warranty, advanced DIYers, getting in there and checking the fasteners might be an off-season project at some point.

That's correct, RT briefly offered a 200ah lithium option but discontinued it in favor of a 400 ah minimum.

I believe both these batteries were built by KS2. The problem early on with the H series was that RT connected the inverter battery charger to the lithium battery discharge terminal which could overcharge and damage the batteries. RT addressed this by shifting the battery charger cable to the charge port. However, KS2 added some protection circuitry to the L1 version that permits charger connection to the lithium discharge port(s).

[markopolo]

Originally Posted by cruising7388

While the AGM is provided to enable the lithium battery BLM to effect a reset, as indicated on the diagram, it is in parallel with the lithium batteries and it's terminal voltage will mirror the lithium battery voltage. I determined by experiment that the RT BLM shuts down the lithiums at approximately 11.95V.

At 11.95V, the AGM SOC is about 40% which isn't significantly detrimental to this battery. However, the wrinkle is that when the lithiums shut down, the inverter, if on, now sees the AGM as its power source and will continue to discharge the AGM until its terminal voltage declines to the shut down point of the inverter which is 10.5 volts. At 10.5 volts, the AGM SOC = ZERO.

Just an FYI - SOC charts on the internet vary greatly.

Here's one that indicates your AGM could be around 15% SOC at 11.95V - https://www.hamiltonferris.com/produ..._Deep_Cycle/16 - scroll down the page.

The charts can be immediate after use voltage, under load voltage or voltage after a long rest and mostly no indication when the battery voltage was measured of if a Flooded or AGM battery: https://marinehowto.com/under-load-b...oltage-vs-soc/

I was looking for examples on the forum and came across a test Booster did: https://www.classbforum.com/forums/f...html#post30129 - 50% SOC was 12.13V right after the test and 12.3V after a rest.

That 12.3V 50% SOC rested voltage matches up with the Marine How To data near the bottom of the page - https://marinehowto.com/under-load-b...oltage-vs-soc/ .

A Trojan Battery chart showing voltage differences between Flooded & AGM:
Trojan Battery AGM vs Flooded SOC Chart.JPG

from Page 22 - https://www.trojanbattery.com/pdf/Tr...UsersGuide.pdf

[markopolo]

Just another FYI - 11.95V for the lithium batteries is very low, getting near zero SOC. Check Winston's data ( LithiumDischargeTable3.jpg ) attached to this post: https://www.classbforum.com/forums/f...tml#post103586

Winston's prismatic cells would be similar to the prismatic cells used in Ecotrek modules. My data for cylindrical cells is here: https://www.classbforum.com/forums/f...tml#post107776 - it also shows not much energy left at all after 12.8V

[markopolo]

cruising7388 thanks for the info you've posted so far. This should end up being a very informative topic.

My understanding is that contactors, solenoids, relays etc. are open or closed. Current flows when closed and doesn't flow when open. I'd guess that the voltage at any point in the system affects the direction of current.

Charge side relay for example:

If LFP 12.7V and AGM 12.8V then current will flow from the AGM to the LFP.
If LFP 12.8V and AGM 12.7V then current will flow from the LFP to the AGM.

What is the voltage range of the charge side trigger set-points?

What is the voltage range of the discharge side trigger set-points?

What would be the optimum voltage range for the charge side voltage trigger set-points?

What would be the optimum voltage range for the discharge side voltage trigger set-points?

--------------------------

The AGM / LFP overlap happens at around 12.8V.

Effectivley

LFP: 13.4V--->12.8
AGM: 12.8V--->12.0V


SOC - State of charge range:
______LFP______AGM______
<--13.4V___________12V-->


---------------

[markopolo]

Was I wrong here: https://www.classbforum.com/forums/f...tml#post120161 ?

If I use that info I get:

Charge side relay closed: 11.5V to 14.4V
Discharge relay closed: 15.2V to 12.4V

Both relays closed overlap: 12.4V to 14.4V so probably highest parasitic losses then.

Inverter operational: 14.4V to 10.5V (inverter LV shutdown)
Coach lights fan etc.: 15.2V to 12.4V Do the lights go out below 12.4V? If no, why not?
AGM linked to inverter: 14.4V to 10.5V
LFP linked to inverter: 14.4V to 11.5V
AGM linked to lights fan etc: 14.4V to 12.4V
AGM linked to LFP: 14.4V to 11.5V
Solar input to LFP possible: 14.4V to 11.5V


Edit: Many, many edits - sorry!

[hbn7hj]

What system uses 24 volts with a combiner?

[markopolo]

Etrek is 12V/24V all AGM.
Ecotrek is 12V LFP AGM

[gregmchugh]

Originally Posted by hbn7hj

What system uses 24 volts with a combiner?

Combiner?

The 8 AGM 6 volt batteries in an eTrek are wired to produce a 24 volt output and a tap in the middle to provide 12 volt power. A battery equalizer is connected between the 24 volt and 12 volt points in the battery bank forcing the 12 volt voltage to always be 1/2 the 24 volt voltage which helps to insure even charging and discharging of the two 12 volt sides off the battery bank. The 12 volt tap in the middle of the battery bank results in more power drawn from the lower 12 volt bank than the higher 12 volt bank which would prevent full charge of both banks without the battery equalizer which insures even charge and discharge of the two banks.

[markopolo]

What's the capacity of the AGM battery in ecotrek equipped coaches?

If 100Ah then an ecotrek 200Ah module and one 100Ah AGM = 300Ah. Add a second ecotrek module and it all becomes 500Ah. It doesn't double to 600Ah as there is still only one AGM as far as I know.

From the KS2 Guide and schematic, there's a path for current from the AGM through the LFP battery to loads when the voltage range is 12.4V to 14.4V as both the charge relay and the discharge relay are closed then.
--------------

Can we devise a easy to do test that helps quantify the parasitic loss?

How about:
1. Plug in overnight to charge the batteries then unplug prior to testing.
2. Block or disconnect solar panel input prior to test.
3. The test is to turn on only a single module and leave it on for 4 hours with no other loads running. So no fridge on, no fan on etc. Run a timer on your phone.

5A parasitic loss for 4 hours = 20Ah.

200Ah-20Ah= 180Ah. 180/200 = 90% SOC

Using Winston's data attached to this post - https://www.classbforum.com/forums/f...tml#post103586 - 90% SOC = 13.36V

That's a rested voltage so turn off the module and measure the voltage after an overnight. OR ............. Resting might not matter because a 5A parasitic load is only a rate of 1/40th C. That's 0.025C (C = capacity) so a small load. (AGM ignored for C rate calculation). Record the not-rested voltage in any case to see if matters. Edited to add: If you add the rest period to the test then solar panel input needs to remain blocked or disconnected.

LFP cells would have excess charge immediately after charging and the AGM would have also have excess surface charge but that excess and surface charge is real and therefore can be used so I wouldn't worry about it boosting the results.

If the end of test voltage is below 13.30V then that would represent a substantial loss of capacity. 70% SOC is below 13.30V on Winston's chart and also on my test results.

Millivolts matter with LFP batteries so you need to at least see the two numbers after the decimal point when measuring LFP voltage.

[markopolo]

Blended LFP / AGM SOC chart*
possible blended LFP AGM SOC chart.jpg

*Data from Winston's chart and Trojan battery AGM chart. Links in posts above.

[cruising7388]

Originally Posted by markopolo

cruising7388 thanks for the info you've posted so far. This should end up being a very informative topic.

My understanding is that contactors, solenoids, relays etc. are open or closed. Current flows when closed and doesn't flow when open. I'd guess that the voltage at any point in the system affects the direction of current.

Charge side relay for example:

If LFP 12.7V and AGM 12.8V then current will flow from the AGM to the LFP.
If LFP 12.8V and AGM 12.7V then current will flow from the LFP to the AGM.

What is the voltage range of the charge side trigger set-points?

What is the voltage range of the discharge side trigger set-points?

What would be the optimum voltage range for the charge side voltage trigger set-points?

What would be the optimum voltage range for the discharge side voltage trigger set-points?

--------------------------

The AGM / LFP overlap happens at around 12.8V.

Effectivley

LFP: 13.4V--->12.8
AGM: 12.8V--->12.0V


SOC - State of charge range:
______LFP______AGM______
<--13.4V___________12V-->


---------------

Our 2017 210 is factory equipped with four lithium batteries and experienced a failure of one of the batteries. When it was replaced at an RT approved repair center, they reported that the AGM terminal voltage was 5 volts and that the battery was toast and replaced it. The cause was not definitely determined but the suspicion was that the particular nature of the lithium battery failure caused a continuous drain on the AGM 24/7. Who knows.