Maximizing PV (Solar) Usage When Connected to Shore Power

[howson]

Update (8 Oct 22): I've learned more! See https://gdrvowners.com/forum/operati...on-setup-again This thread is now closed.

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Update (24 June 2021): Using ESS in a mobile ("RV") setup is not recommended by Victron or supported by AMSolar. After a lot of trial and error what I've learned is summarized in posts 53 and 54. Please either read just posts 53 and 54 or read the entire thread. (Don't stop in the middle!)

--Start of original first post--

This post may be lengthy--forgive me in advance as I attempt to be comprehensive and brief at the same time.

When at home my 315RLTS is always connected to a stable, always-on 50A shore power connection. What you'll see in the graphs below is an "AC Loads" of ~370W (watts). That's a dehumidifier that's always on. Since I recently installed solar power on my trailer, I want to use solar ("PV") when it is available. In other words, I want PV usage prioritized over shore power but without using my Battle Born batteries in the process.

To summarize:
1) Do not use inverted 12v Battle Born power to run 120vAC loads when connected to shore power at home.
2) Keep the Battle Born batteries fully charged.
3) Supplement shore power with solar when available.

What must be understood first is that a "normal" DC-coupled PV system with an Victron MPPT controller is designed to charge the battery bank, not to directly run loads. Below is a typical setup (diagram is modified from a Victron original).



Note: I'm going to use "battery" as a generic term for a single or bank of batteries.

The problem is in the standard configuration, when the battery is fully charged the PV output drops to 0 even when there are active AC loads unless the battery is being utilized as a power source!

Let's back up for a second. Below is a screen shot from my Color Control ("CCGX") after the initial installation of my solar setup. The Victron components are networked together but are working independently (as designed). Note there is plenty of PV Charger voltage available (37.19v) but the controller has turned off the current flow because the battery is fully charged and shore power is available. In this condition shore power is prioritized so the battery is not being utilized by the inverter. Bottom line--all of the power going to AC Loads is from the Grid. What a waste!



After a bit of research I discovered there's an add-on (called an "Assistant") that can be loaded into the Multiplus Inverter to accomplish my purpose. The newest version is called ESS which is short for Energy Storage System. There are older assistants that can do the same thing but they are no longer supported by Victron (they are labeled as "deprecated").

I loaded the ESS Assistant (a subject worthy of its own thread!) and immediately got fault Exciting new Forum! I had to go into the MPPT through the VictronConnect app and remove it from the network. This is also a subject for a separate thread so I won't go into detail. Bottom line: the Victron SmartSolar MPPT is now under the control of the Victron Multiplus through the ESS Assistant.

If you want to deep dive into the ESS system, Victron's manual is here: https://www.victronenergy.com/live/e...llation-manual

Once I had the ESS Assistant loaded I experimented with multiple modes, but always ran into the problem--the PV Charger output dropped to 0W once the batteries were charged. The only time I could get it to work as desired was to utilize battery power, but I didn't want to do that. In the picture below, no PV power is going to the AC Loads. Only a trickle of the power available is going to the battery to keep it topped off. Again--there's PV power being wasted!



Here's another setting I tried, "Optimized (with Battery Life), that didn't work. Note the SOC ("State of Charge") was set to 100% to keep the battery from being discharged.




What finally worked (as discovered in the manual) was turning on a setting labeled DVCC (Distributed Voltage and Current Control) and setting the ESS Assistant to Keep Batteries Charged. Below is how I currently have the system configured. I'm not 100% sure this is 100% correct, but it's working! Note that the Grid is now only supplying what the PV Charger cannot supply (it's very cloudy and overcast today).



I hope some of this makes some sense--would love some feedback from others with a Victron setup like mine or have a workaround that prioritizes PV power over shore power.

-Howard

[howson]

One of the (very cool!) features of the Victron setup is the ability to monitor the system over the internet. I'm sitting in my office and have the "Remote Console" (an exact duplicate of the CCGX display) running on my computer as I type this so I can see what's happening.

It's another foggy, overcast day here in NW Florida but I watched the PV Charger wattage increase as it got lighter outside . Started around 30W at 7am, so all available PV power was going to self-power the MPPT Controller and (very occasionally) top off the Battle Borns. Now it's around 10am and, while still heavily overcast, the panels are generating more power. Here's what I'm currently seeing:



If you're not familiar with the diagram, power is flowing ("marching ants") from the PV Charger (a Victron SmartSolar MPPT Controller) to the Battle Born batteries and also to the Victron Multiplus Inverter. The power required by AC LOADS exceeds available PV Charger output, so the Grid is supplying the difference. Exactly what I want it to do!

[howson]

PART 1 of 2: SYSTEM TESTING AND CONFIGURATION DOCUMENTATION

Finally got a sunny day to do some testing. (Weather has been awful!) This post will be in two parts, the first being the testing results and part 2 the settings used in the Victron Multiplus and Energy Storage System Assistant.

I am not an expert on this stuff--I'm learning as I'm going. I'd definitely appreciate feedback from other Victron component owners! Even if you just have a question or comment it may spark further investigation, so don't hesitate to jump in.

If you are a new reader or haven't read the related thread, the solar system install thread is here: https://gdrvowners.com/forum/solar/1...n-2019-315rlts

SLIDE 1: Nothing much of interest here other than seeing the results based on the conditions. Hopefully the reader can orient the comments to the Color Control GX ("CCGX") display snapshot. I added the red arrows to show what the "marching ants" were doing on the display. Not sure why there is a difference between power available and power consumed.



SLIDE 2: Again, not much here other than the results of the sun getting stronger and changes to the AC LOADS.



Slide 3: Now it gets interesting. Why did PV Charger output drop to only 553W while charging the battery when I turned off all AC Loads? (As you'll see in a later slide, the batteries can absorb almost 100A and there is the same amount of sunshine outside, so no obvious reason for the low power output.) Note how in 1217 when AC Loads are turned back on that the PV Charger wattage jumps back up. ???



Slide 4: Turned off AC Loads and confirmed--again--the drop in PV Charger output. I then went into VE Configure (plug in to the Multiplus with a laptop) and went through the settings. Part 2 (separate post) has the setting slides. Note how at 1305, with the AC Loads again off, the PV Charger output is much higher (batteries are taking 56.1A instead of the former 36.2A).



Slide 5: Turned on shore power ("Grid"). Batteries now charging at 98.8A. Arrow flow is an educated guess. What's of interest here is the display from 1436. Even when there is plenty of PV available, the Multiplus continues to draw a small amount of power from the Grid.

[howson]

PART 2 of 2: SYSTEM TESTING AND CONFIGURATION DOCUMENTATION

The purpose of this post is to document my settings. I do not know if they are 100% correct. Honestly--I'll probably mess around with the Energy Storage System (ESS) settings and test more in the future. For the near term this will have to do.

UPDATE, 11 Mar: I now know the settings shown in this post do not work. I've left them here for thread continuity, but do not use them.

SLIDE 6: Distributed Voltage and Current Control (DVCC) was turned on in the Color Control GX (CCGX). ESS is what Victron calls an Assistant, which in reality is a software "app" that is loaded into their inverter through a laptop. (How to do all that is outside the scope of this post.) The slide below shows my current settings.



SLIDE 7-10: These are the screenshots while I was in VEConfig. in other words, I had my laptop connected to my Victron Multiplus 12/3000 and as I went to each screen I snapped a screen shot. I made sure each setting matched what was in the BMV-712 (battery monitor) and the Victron SmartSolar Charge Controller.





Not sure if I selected the right battery type--will have to check with AMSolar. I also not sure I have the Sustain Voltage setting correct.



I really have no idea what these settings are or if they are correct. I left them at the default. I know I don't have a PV Inverter! (To the best of my knowledge, a "PV Inverter" is not the same as an MPPT controller, it's a solar charger connected to the grid. Like in a house configuration without batteries.)

[koolrayz]

I just bought a 260rd and have been racking my head trying to figure out why I haven't seen this addressed before. Thank you so much for sharing!

[howson]

Performed more testing today. When I disconnected shore power to run off the batteries to ensure everything still worked as before with the refrigerator (PV wasn't strong enough yet) the battery voltage dropped within minutes to levels that forced to inverter to completely turn itself off. I was able to repeat the errant behavior multiple times but could not figure out why.

Without boring you with tons of snapshots and configurations I'll skip to the end: I removed the ESS assistant and turned off DVCC. I was then able to run the batteries down to ~19% and recharge them to full capacity using shore power. Unfortunately, as I found originally with this configuration, when on shore power the PV Charger's capability is ignored. That's a real bummer. Example below. Of note, the "marching ants" are coming from the inverter (thus the 1616W being pulled from the grid) to the battery and no wattage is coming from the PV Charger. It was a beautiful day and there was well over 800W of PV available but it had shut itself off. :(

[howson]

Whew...read, read, read and another hour on the phone with Battle Born. They don't even know anything about DVCC! <sigh> But they are willing to dig in and investigate, so (hopefully) I'll know more soon.

A couple of references: https://www.victronenergy.com/live/b...ity:battleborn Unfortunately this document is in draft mode since Apr '19. :(

CCGX manual (https://www.victronenergy.com/live/c...urrent_control) in chapter 4: DVCC - Distributed Voltage and Current Control

11 Mar Update: Again, I now know the settings in this post are wrong. Left here to show what NOT to do and if you read the entire thread it will make sense.

Here's the current settings and rationale:



DVCC: Obviously must be on for the other settings to be available.

Limit Charge Current: According to the CCGX manual, This is a user-configurable maximum charge (my emphasis)current setting. It works across the whole system. MPPT Solar Chargers are automatically prioritized over the mains/generator. Unfortunately I think this only applies to charging the batteries, not power being used by AC Loads. Thus if the batteries are at 100% PV Charger power may not be routed to the inverter for AC Loads. I guess I'll find out tomorrow when the sun comes up.

Maximum Charge Current: 100A is typically the highest current flow I see when the Battle Borns are being charged by the Multiplus (on shore power), so that's why I chose that figure.

SVS - Shared Voltage Sense: Per the CCGX manual, The system automatically selects the best available voltage measurement. It will use the voltage from the BMS or a BMV battery monitor, if possible, otherwise it will use the battery voltage reported by the VE.Bus system. I *think* this is the setting under System Setup > Battery Monitor (see pic below). As you can see I have it set to Automatic.

I don't completely understand the difference between VE.Direct and VE.Bus, but it may just be the cable used to interconnected the components. I know the Multiplus is connected to the CCGX by an ethernet cable and the BMV-712 is connected to the CCGX by a VE.Direct cable. So if I'm interpreting the manual correctly the BMV's reading/measurement/value/percentage has priority and then, if the BMV's is not available, DVCC will use what voltage the Multiplus is sensing.

7 Mar edit: Updated wiring info--I had it wrong. The RJ-12 ("small" ethernet-looking cable) is from the BMV-712 to the shunt.





Shared Temperature Sense: The Battery Management System (BMS) in the Battle Borns take care of temperature control. There is no need for temperature compensation with a LifePo4 battery. I see no need to turn this on.

Shared Current Sense: According to the SmartSolar's manual, The MPPT Solar Chargers will also end absorption and switch to float when the battery current drops below a low current threshold limit, the ‘tail current’. The default tail current value is 2A. By turning SCS on, what the BMV is measuring through it's shunt is reported to the SmartSolar controller. (I think.) On the BMV-712 the tail current setting is 2%. Since I normally see 100A when the batteries are charging in bulk mode, so this mean the BMV reports tail current as 2A? (100 * .02 = 2) Frustrating that the BMV uses on value (percentage) and the SmartSolar controller uses an actual amperage value.

I've probably lost the majority of those who dared to start reading this post. I guess it's mainly for me--as I try to explain it I have to dig in even further to make sure I understand what I'm writing.

Any questions...fire away. I'll keep experimenting and sharing what I learn to do (and what not to do!).

-Howard

[howson]

Update (4 Mar): Victron does not recommend using DVCC and ESS in mobile applications. See next post for more information.

A LOT of testing and configuration changes again today. Too much to post. I've sent a document to AMSolar and Battle Born to get their input on the settings. I will, or course, update and post if appropriate.

Howard

[howson]

Victron does not recommend DVCC and ESS for RV installations. The quote below is from a Victron representative via AMSolar:

"Hi, The main reason is that when ESS is enabled, even if grid-feedback is disabled, the input relay on the Multi is closed. The system still uses the grid as a small “buffer” for surges and spikes. It needs to be able to draw from the grid in milliseconds to support loads. As long as the input relay is closed, any connected wiring is also live. So shore power sockets can be live and can fool people into thinking they are safe. This is why we specify fixed (hard-wired) installations only."

So, again, the official word is Victron does not recommend DVCC and ESS for RV installations. AMSolar will not discuss any of the ESS or DVCC settings with me based on Victron's response.

I will repeat here that I am not an electrician nor an engineer of any sort. But Victron's response makes no sense to me. For the grid to provide a "small buffer", by definition there must be shore power (120vAC) available through the external power connection. I have no idea how someone could consider shore power sockets anything other than "live" with power applied. I don't understand how someone could be "fooled" into thinking the external power connector was "safe" when shore power is applied.

So let's assume for a moment that what the Victron rep was stating is that with shore power OFF there is a possibility of backfeed through the system to the RV's external power connector. Without an automatic transfer switch that could be true. But who installs an inverter and upgraded batteries in their RV without some form of transfer switch? In addition, the hardwired Progressive Dynamics EMS in my system also prevents backfeed (I confirmed with Progressive). If what the Victron rep is stating was truly a hazard how can there be generators in 5th wheels? Wouldn't their generated 120vAC "fool" people into thinking the external power connector is safe? (It is, of course, safe due to the action of the automatic transfer switch.)

As I have my system currently configured I personally see nothing unsafe. I know the system cannot backfeed--it would mean catastrophic failure of the ATS and EMS simultaneously. (I confirmed with Progressive that power cannot backfeed through the EMS. Somehow the output of the inverter would need to be tied to the input side of the EMS for power to get to the external power connector. Who would do that?) Another clue is that my EMS' status screen is blank when shore power is off, thus reflecting that the EMS is powered off.

So where am I at in this project? I still don't know if some of the settings for a few of the ESS screens are correct. I'm going to keep after AMSolar, though, to get the numbers. I'll continue to update this thread.

I will repeat that if anyone chooses to try and duplicate what I've done they do so at their own risk. Unless you are willing to accept that risk and any consequences associated with your configuration, don't attempt to run DVCC and ESS in your Victron setup.

[Guest]

Performed more testing today. When I disconnected shore power to run off the batteries to ensure everything still worked as before with the refrigerator (PV wasn't strong enough yet) the battery voltage dropped within minutes to levels that forced to inverter to completely turn itself off. I was able to repeat the errant behavior multiple times but could not figure out why.

Without boring you with tons of snapshots and configurations I'll skip to the end: I removed the ESS assistant and turned off DVCC. I was then able to run the batteries down to ~19% and recharge them to full capacity using shore power. Unfortunately, as I found originally with this configuration, when on shore power the PV Charger's capability is ignored. That's a real bummer. Example below. Of note, the "marching ants" are coming from the inverter (thus the 1616W being pulled from the grid) to the battery and no wattage is coming from the PV Charger. It was a beautiful day and there was well over 800W of PV available but it had shut itself off. :(

Howard,

What fascinating work you are doing! I'm taking a shot at the low charge rates where it looks like the MPPT is in the float portion of the charge profile such as at 1205 as an example. Is there a hysteresis setting in your MPPT control? This would provide the high low limits in when you would want the bulk charging to come into play. Otherwise you could get into hunting in and out of the bulk mode or sit in float mode until the batteries discharge to some low SOC.

For the losses, each item in the system would have some losses due to lost efficiency and would convert some energy into heat.

For temperature sense: If your MPPT charge profile is adjusted for high or low temperatures, this would be a valuable feature IMO and would result in increased battery life.

Jim

[howson]

Is there a hysteresis setting in your MPPT control? This would provide the high low limits in when you would want the bulk charging to come into play. Otherwise you could get into hunting in and out of the bulk mode or sit in float mode until the batteries discharge to some low SOC.

No hysteresis setting that I know of, Jim. The VictronConnect App is the only way I know of to configure the SmartSolar device and there's nothing even close to "hysteresis" (or the effect).

For the losses, each item in the system would have some losses due to lost efficiency and would convert some energy into heat.

I agree. What I don't know is if the losses I am seeing are "normal" given my configuration.

For temperature sense: If your MPPT charge profile is adjusted for high or low temperatures, this would be a valuable feature IMO and would result in increased battery life.

For Battle Born batteries they recommend leaving Temp Comp off. From the manual: Temperature Compensation Temperature compensation is not needed with our batteries and in some cases, may trigger the built in BMS to go into protect mode. For this reason, we recommend that temperature compensation be shut off or set to 0.

[Guest]

Not understanding their claim on temperature compensation where as an example, a 100amp charge for a single 100ah battery would do damage at <25F (low temp charge cut off) but would be ok if charging 100amp at 26F? It does not work this way. But they are recommending it not be used so I would follow their advice.

I did notice in the BB manual they recommend a 20 minute absorption charge for each battery after exiting bulk mode. Is there a setting in the MPPT that would be keeping the charger in absorption or float for a specified time with a reduced load?

From the BB manual:

Bulk/Absorption
For your Bulk/Absorption stage, the ideal voltage is between 14.2v-14.6v. For full charge and balance, the absorption mode should be set to last for at least 20 minutes per battery (for multiple batteries in parallel).

Float
Our batteries do not need a float stage for charging, but a float voltage between 13.4V and 13.8V can be used when connected to shore power.

Cool stuff you are doing and the gadgetry is amazing.

Jim

[howson]

Not understanding their claim on temperature compensation where as an example, a 100amp charge for a single 100ah battery would do damage at <25F (low temp charge cut off) but would be ok if charging 100amp at 26F? It does not work this way. But they are recommending it not be used so I would follow their advice.

I did notice in the BB manual they recommend a 20 minute absorption charge for each battery after exiting bulk mode. Is there a setting in the MPPT that would be keeping the charger in absorption or float for a specified time with a reduced load?

From the BB manual:

Bulk/Absorption
For your Bulk/Absorption stage, the ideal voltage is between 14.2v-14.6v. For full charge and balance, the absorption mode should be set to last for at least 20 minutes per battery (for multiple batteries in parallel).

Float
Our batteries do not need a float stage for charging, but a float voltage between 13.4V and 13.8V can be used when connected to shore power.

Cool stuff you are doing and the gadgetry is amazing.

Jim

Yes, there's a Float time setting. BB says 30 min per 100aH battery. AMSolar says 30 minutes regardless of how many batteries are in the system. I emailed Garret directly to ask if it was a typo and he quickly responded that AMSolar is adamant about no more than 30 minutes, period. Gotta love it when the "experts" don't even agree. <sigh> (I went with AMSolar's recommendation, as my entire configuration is per their recommendations with the notable exception of the DVCC and ESS.)

If you go here: https://amsolar.com/rv-solar/support and look down the Battle Born column you'll see the 30 minutes I am referencing.

[Guest]

Howard,


You may want to try the same experiment as closely as possible and wait the 30 minutes @ 1205 to see if the MPPT eventually moves to bulk mode. Curious also what your Victron BMV712 is reporting on SOC on your 400ah battery pack at that time?

Jim

[howson]

Howard,


You may want to try the same experiment as closely as possible and wait the 30 minutes @ 1205 to see if the MPPT eventually moves to bulk mode. Curious also what your Victron BMV712 is reporting on SOC on your 400ah battery pack at that time?

Jim

The number on the the "battery" (lower left of the CCGX screenshot) is the same as the BMV-712. There are sometimes very small percentage differences (99.7% vs 100%, etc) but the advantage of going "all in" on Victron components is they share information. The CCGX is the key--it's way more than just a colored screen.

I will run the test again today and post later.

Howard