Lithium 80% DOD rule

[gregmchugh]

Originally Posted by markopolo

Would you mind posting the voltage along with the SOC % at various levels of discharge? That bit of data could be very useful to those who don't have the level of monitoring that you do and also interesting to those of us with lead acid batteries.

That would be quite a task, I think, unless there is a log file somewhere with the data. As shown in the Elite battery curves I posted, which may still be battery used by ARV in the 200AH size, the voltage curve will be dependent on the load. To produce the data without a log file you would have to put a significant load on the battery bank and record the data on the screen at regular intervals for many hours as the batteries discharge to the 20% state of charge.

Basically, the same test used to create the curves using various constant loads..

[cruising7388]

Originally Posted by Davydd

For starters I have 16 200ah 3.2v LiFeP04 cells with four in series to make a nominal 12v which is actually closer to 13.8v fully charged. Four in parallel give me the nominal 800ah published. When the the battery bank uses 640ah (80% DOD) then the bank automatically shuts down completely. I then have to manually restart it by physically holding down a toggle switch with shore power plugged in or the engine running for up to 6 minutes or 1% SOC before the batteries reconnect.

You have to hold down a toggle switch for six minutes to bring the batteries back on line?

[markopolo]

Originally Posted by gregmchugh

That would be quite a task, I think, unless there is a log file somewhere with the data. As shown in the Elite battery curves I posted, which may still be battery used by ARV in the 200AH size, the voltage curve will be dependent on the load. To produce the data without a log file you would have to put a significant load on the battery bank and record the data on the screen at regular intervals for many hours as the batteries discharge to the 20% state of charge.

Basically, the same test used to create the curves using various constant loads..

Yes, that would be quite the job. It's not what I meant though. I should have asked if he could compare (occasionally) what his monitor shows to the Shorai chart.

Shorai SOC chart.gif

That's what I was going to do with any data he provided. I was thinking casual observance; after using the induction cook top on day 2 or after Keurig use on day 1 etc. It would have to be after large loads so there be the least amount of current draw. Early morning and late evening might be best because of solar panel input.

If his data roughly matches the Shorai or Thundersky chart then it would give folks who don't have that level of monitoring a better idea of what their SOC would be at a give voltage when under minimal load.

[booster]

Originally Posted by gregmchugh

These curves show discharge under loads for cells similar to the ones used by Roadtrek and ARV...


http://elitepowersolutions.com/docs/...g%20Curves.pdf

Those curves show exactly what what we have been talking about. At all fixed loads, they have a very flat curve over the entire midrange of the SOC, barely over .1v change in the usable range. The curves also show that the load does affect the voltage, although the affect probably is pretty small in big battery banks, for the %C vans are usually running at. Smaller banks, at bigger loads, would have more error.

It would be interesting to see how long it takes the batteries to bounce back to stable voltage when power is removed.

[booster]

Originally Posted by markopolo

Yes, that would be quite the job. It's not what I meant though. I should have asked if he could compare (occasionally) what his monitor shows to the Shorai chart.

Attachment 3694

That's what I was going to do with any data he provided. I was thinking casual observance; after using the induction cook top on day 2 or after Keurig use on day 1 etc. It would have to be after large loads so there be the least amount of current draw. Early morning and late evening might be best because of solar panel input.

If his data roughly matches the Shorai or Thundersky chart then it would give folks who don't have that level of monitoring a better idea of what their SOC would be at a give voltage when under minimal load.

That would probably be about the only way someone without a SOC monitor could know what is going on. It would certainly require a very good voltmeter and wiring to it, though. You would need a meter that displayer to .001v with probably no more than +/- .002v accuracy, which is way beyond the common RV stuff used in the monitors and such.

[Davydd]

Originally Posted by cruising7388

You have to hold down a toggle switch for six minutes to bring the batteries back on line?

I said up to 6 minutes to get a registerable 1% SOC increase with shore power. I can shut the battery down manually and if the SOC is greater than 20% the batteries will come back online within a couple seconds. It is ARV's method I guess as a way to get a recharge of the batteries started. The battery bank will automatically shut down as I said if DOD reaches 80% or if the battery temperatures drop below 41 deg. F. (maybe 36 deg. as I am not sure what their set point is). Those are just failsafe protections since there is Autogen and batteries heaters built in.

How do I know all this? What ARV says in their manual and my deliberate testing to see if it works as stated and to observe for myself.

[Davydd]

Originally Posted by markopolo

Would you mind posting the voltage along with the SOC % at various levels of discharge? That bit of data could be very useful to those who don't have the level of monitoring that you do and also interesting to those of us with lead acid batteries.

I suppose I could look back at some of my various photos of the Silverleaf screen to see what voltage was at various SOCs. But to monitor it without the ability to automatic record to a computer printout would be like watching paint dry. There is a computer plug in module at our control panel behind the Silverleaf screen that ARV uses to record and program. I don't have that kind of software. I could plug into my solar module and record that info to a computer but it takes a Windows PC for the software and hardware I don't have or care to have.

What is important to me is to note a SOC % before say brewing a couple of cups of coffee with a Keurig and then noting it after. Then you can roughly calculate with known information about the Keurig, the time it is on and compare it to the percentage change to figure out the amp hour drop in the battery. It has gotten to the point where I can confidently say I don't have to bother to worry about my electrical use for at least two days boondocking no matter what I do.

The inverter when on draws about 4-6 amps per hour. The refrigerator about 3-5 and there is about 2-3 amps per hour for everything else connected (alarms, idiot lights, standby stuff, wifi, microwave window, Silverleaf screen, Trik-L-Start, Pioneer receiver.) I now figure a budget of about 10 amps per hour plus any other electrical use I might employ. As I mentioned, I rarely turn the inverter off to conserve the battery as Roadtrek recommends for their Bs. Doing that means I would have to reset the microwave LED clock every time or watch the display annoyingly blink. The other thing is our articulating beds operate off AC power and I am constantly adjusting them when using them. We use our Keurig often during the day at rest stops and such. It is just inconvenient to shut the inverter off and lose AC power. As I mentioned boondocking or shore power or electrical use is transparent.

[gregmchugh]

Originally Posted by Davydd

I said up to 6 minutes to get a registerable 1% SOC increase with shore power. I can shut the battery down manually and if the SOC is greater than 20% the batteries will come back online within a couple seconds. It is ARV's method I guess as a way to get a recharge of the batteries started. The battery bank will automatically shut down as I said if DOD reaches 80% or if the battery temperatures drop below 41 deg. F. (maybe 36 deg. as I am not sure what their set point is). Those are just failsafe protections since there is Autogen and batteries heaters built in.

How do I know all this? What ARV says in their manual and my deliberate testing to see if it works as stated and to observe for myself.

I assume the Silverleaf system is powered from the chassis battery and is active all the time even when the lithiums are shutdown? Or is it off when the lithiums are shutdown?

Do you also get the battery status info from the display when the lithiums are shutdown? If so, that means the battery management system is also powered from the chassis battery which is no problem given the low power draw in the ARV BMS.

[Davydd]

Originally Posted by gregmchugh

I assume the Silverleaf system is powered from the chassis battery and is active all the time even when the lithiums are shutdown? Or is it off when the lithiums are shutdown?

Do you also get the battery status info from the display when the lithiums are shutdown? If so, that means the battery management system is also powered from the chassis battery which is no problem given the low power draw in the ARV BMS.

No, the Silverleaf screen goes off when the batteries go off line. The coach is totally separate from the chassis as the second alternator does the charging. The toggle switch I mentioned is a mechanical switch. When the batteries reconnect the Silverleaf screen comes back on.

That toggle switch is also used to shut down the battery bank for winter storage if you prefer. With the batteries off line there is little chance they would deplete over a winter storage. I do in Minnesota have that -4 deg. F. concern so will stay plugged in with outside storage. BTW, Advanced RV was not aware of the -4 deg. limit for lithium ion batteries before last spring. If you look back at anything available on the Internet, very few were aware of it. It was always just mentions that you still had about 80% battery capacity at that temperature but no mention of damage. The only mention of damage was trying to charge at below freezing. My guestimate is the outside temperature would have to get down to about -20 F. for the internal battery temperatures to drop to -4 when online. That could happen in Minnesota easily.

[gregmchugh]

Originally Posted by Davydd

No, the Silverleaf screen goes off when the batteries go off line. The coach is totally separate from the chassis as the second alternator does the charging. The toggle switch I mentioned is a mechanical switch. When the batteries reconnect the Silverleaf screen comes back on.

That toggle switch is also used to shut down the battery bank for winter storage if you prefer. With the batteries off line there is little chance they would deplete over a winter storage. I do in Minnesota have that -4 deg. F. concern so will stay plugged in with outside storage. BTW, Advanced RV was not aware of the -4 deg. limit for lithium ion batteries before last spring. If you look back at anything available on the Internet, very few were aware of it. It was always just mentions that you still had about 80% battery capacity at that temperature but no mention of damage. The only mention of damage was trying to charge at below freezing. My guestimate is the outside temperature would have to get down to about -20 F. for the internal battery temperatures to drop to -4 when online. That could happen in Minnesota easily.

Thanks for the info...

[cruising7388]

Originally Posted by Davydd

The inverter when on draws about 4-6 amps per hour. The refrigerator about 3-5 and there is about 2-3 amps per hour for everything else connected (alarms, idiot lights, standby stuff, wifi, microwave window, Silverleaf screen, Trik-L-Start, Pioneer receiver.) I now figure a budget of about 10 amps per hour plus any other electrical use I might employ. As I mentioned, I rarely turn the inverter off to conserve the battery as Roadtrek recommends for their Bs. Doing that means I would have to reset the microwave LED clock every time or watch the display annoyingly blink. The other thing is our articulating beds operate off AC power and I am constantly adjusting them when using them. We use our Keurig often during the day at rest stops and such. It is just inconvenient to shut the inverter off and lose AC power. As I mentioned boondocking or shore power or electrical use is transparent.

Does the inverter draws 4-6 amps from the batteries when it idles with no load demand?

Leaving your inverter on makes sense because you have 800 ah capacity, so with this level of suds the inverter idle load is of little consequence. Roadtrek's situation was different because they delivered some coaches with a single 200 ah lithium which obviously dictates a higher level of conservation, prompting the caution to shut off the inverter when not in use. This made no marketing sense because the 200 ah lithium battery was a $2500 option, but if the underhood generator was ordered, it came with 400 ah AGM batteries with as five year warranty at no extra charge. Any lithium battery option deleted the AGMs. They no longer offer a 200 ah lithium option which now starts at 400 ah up to as much as 1600 ah on some models.

Early on, their inverter was off the shelf and included a power saver feature that would periodically check for a load demand. However, apparently it would stimulate the microwave into a beeping mode with each inquiry. So in current production, their inverter is specially built for them and the power save mode is deleted. By their own acknowledgement, the standby mode draws about 8 amps which IMO is unacceptably high for a modern inverter design.

[avanti]

Originally Posted by cruising7388

Does the inverter draws 4-6 amps from the batteries when it idles with no load demand?

My Outback inverter (which is the same as DavyDD's) draws 2.3 amps at idle. He, of course, has the Silverleaf system and other loads which I am guessing he is including in his number. My number is ONLY the inverter plus whatever it takes to run the clock on the microwave.

[cruising7388]

Originally Posted by Davydd

I said up to 6 minutes to get a registerable 1% SOC increase with shore power. I can shut the battery down manually and if the SOC is greater than 20% the batteries will come back online within a couple seconds. It is ARV's method I guess as a way to get a recharge of the batteries started. The battery bank will automatically shut down as I said if DOD reaches 80% or if the battery temperatures drop below 41 deg. F. (maybe 36 deg. as I am not sure what their set point is). Those are just failsafe protections since there is Autogen and batteries heaters built in.

How do I know all this? What ARV says in their manual and my deliberate testing to see if it works as stated and to observe for myself.

Considering the level of refinement that ARV offers for their electrical system, this seems a little primitive. When your DOD is >80% and the BMS shuts down, what is the power source that stimulates a BMS reboot?

Roadtrek had an issue regarding bringing their BMS back on line after shut down which they resolved by adding a stand alone AGM that provides for a fast reboot. Curiously, they now recommend that regardless of the battery state, any battery shut down should not simply be turned back on, but should be reset.

[booster]

Our inverter is a Magnum MS2000, 100 amp charger, 2000 watt PSW inverter and it uses just under 1.5 amps when on with no load. If you put it into the search mode, which is like what RT used to have available, it will go down to a couple of tenths of an amp IIRC. We don't use the search, as our inverter is nearly always off unless we are using a high load AC device. All our normal use stuff is on 12v outlets, so no AC needed.

[Davydd]

Originally Posted by cruising7388

Considering the level of refinement that ARV offers for their electrical system, this seems a little primitive. When your DOD is >80% and the BMS shuts down, what is the power source that stimulates a BMS reboot?

Roadtrek had an issue regarding bringing their BMS back on line after shut down which they resolved by adding a stand alone AGM that provides for a fast reboot. Curiously, they now recommend that regardless of the battery state, any battery shut down should not simply be turned back on, but should be reset.

I'm not sure what is so primitive about it. They come back online when 21% SOC is achieved by shore power charging or running the engine. What Roadtrek does with AGMs mystifies me.

1% is 8ah. It would theoretically take about 4-1/2 minutes of shore power charging to charge the battery 8ah. If I high idle the engine and charge with the dual alternator it would take about 2 minutes to come back online.

It is just a standard toggle switch. To disconnect the batteries just flip it down. To reconnect the batteries that have a SOC greater than 21% just flip it up and press until reconnect is complete. That is pretty much instantaneous unless a charge has to be built up to register. I'm not sure why I have to physically press and hold the toggle switch. I suppose it could be designed differently but then would add complexity and something else less positive feedback to go wrong for a seldom needed function.

[avanti]

Originally Posted by booster

Our inverter is a Magnum MS2000, 100 amp charger, 2000 watt PSW inverter and it uses just under 1.5 amps when on with no load. If you put it into the search mode, which is like what RT used to have available, it will go down to a couple of tenths of an amp IIRC. We don't use the search, as our inverter is nearly always off unless we are using a high load AC device. All our normal use stuff is on 12v outlets, so no AC needed.

Yes, we operate exactly the same way. The Outback (which is 2800 watts, BTW) also has search mode, and we also do not use it, for the same reason. The Outback has a dry contact input that can be programmed to turn the inverter on or off without having to use the menu system on the panel. I wired this to a very convenient (and well-labeled) toggle switch on a marine switch panel. This makes it extremely easy to flip on the inverter if we want to use the microwave, the Keurig, the A/C or a hair dryer, which are the only 120VAC devices we ever use. All media (including a modified AppleTV) and datacomm are 12VDC native, and we have 12V chargers for all devices (including our MacBook Pros).

[cruising7388]

Originally Posted by booster

Our inverter is a Magnum MS2000, 100 amp charger, 2000 watt PSW inverter and it uses just under 1.5 amps when on with no load. If you put it into the search mode, which is like what RT used to have available, it will go down to a couple of tenths of an amp IIRC. We don't use the search, as our inverter is nearly always off unless we are using a high load AC device. All our normal use stuff is on 12v outlets, so no AC needed.

Which is why I raised the question. I also have a Magnum inverter/charger and I experience the same idle load you do when active. I previously had a Prosine inverter/converter 2.0 that drew <2 amps when active. These designs are a couple of decades old. You would think that the current generation inverters would have lower idle power requirements, not higher.

[booster]

Originally Posted by avanti

Yes, we operate exactly the same way. The Outback (which is 2800 watts, BTW) also has search mode, and we also do not use it, for the same reason. The Outback has a dry contact input that can be programmed to turn the inverter on or off without having to use the menu system on the panel. I wired this to a very convenient (and well-labeled) toggle switch on a marine switch panel. This makes it extremely easy to flip on the inverter if we want to use the microwave, the Keurig, the A/C or a hair dryer, which are the only 120VAC devices we ever use. All media (including a modified AppleTV) and datacomm are 12VDC native, and we have 12V chargers for all devices (including our MacBook Pros).

Having a one push switch for the inverter is a really nice feature. On the Magnum remote, they have separate on/off buttons for both the charger and inverter sections and we have it mounted right in the most convenient place it could be, so works great. We also have several programmable shortcut buttons for common things which we use for amps, AH down, volts, etc so no menu scrolling. The Blue Sky solar controller has lots of information and flexibility, but it seems that the more you need the screen, the further down the menus it is. I think some of the ones I like are 20 screens in, with no way to shortcut them or move their locations. Nice controller, but a PITA to monitor or change things.

[cruising7388]

Originally Posted by Davydd

I'm not sure what is so primitive about it. They come back online when 21% SOC is achieved by shore power charging or running the engine. What Roadtrek does with AGMs mystifies me.

1% is 8ah. It would theoretically take about 4-1/2 minutes of shore power charging to charge the battery 8ah. If I high idle the engine and charge with the dual alternator it would take about 2 minutes to come back online.

It is just a standard toggle switch. To disconnect the batteries just flip it down. To reconnect the batteries that have a SOC greater than 21% just flip it up and press until reconnect is complete. That is pretty much instantaneous unless a charge has to be built up to register. I'm not sure why I have to physically press and hold the toggle switch. I suppose it could be designed differently but then would add complexity and something else less positive feedback to go wrong for a seldom needed function.

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.

[gregmchugh]

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.

In the most common Roadtrek configuration here is how the AGM is wired into the system and gets charged.

The AGM is connected to the charge terminal on all the Ecotrek modules along with the underhood generator and the solar charge controller.

The inverter/charger and the 12v loads are connected to the load terminal on all the Ecotrek modules.

The AGM, therefore, is always being charged by the underhood generator and the solar charge controller.

At any time when at least one Ecotrek is online with both the charge and load relays closed then the AGM is also connected to the inverter and the 12v loads and is simply in parallel with the Ecotreks. In this case, if on shore power, the AGM also gets charged in parallel with the Ecotreks by the charger in the inverter.