BCM Community
Bus Discussion => Bus Topics ( click here for quick start! ) => Topic started by: epretot on August 12, 2023, 07:48:54 PM
-
Quick solar question.
I'm setting up my charge controllers for the solar and battery bank. My batteries have a recommended charge current of 40 amps. The maximum is 50 amps.
Here is my question. Because I have dual controllers, should I set the charge controllers to 20-25 amps? Or 40-50?
It makes sense to cut it in half. But then I considered the bank being series/paralell might allow for a greater charge current.
Any help is appreciated.
-
Do you have enough solar panels that you can exceed this charge limit? Do both solar arrays output in sync or does one produce more more power in the morning and the other in the afternoon?
If you have Victron equipment you can have a GX control computer where you implement DVCC (distributed voltage charge control). Which would automatically balance between the two charge controllers to do maximum charging.
But it sounds like you already have your charge controllers, so yes set them both to 20 AMP's and maybe have less than full production.
-
Thanks for the quick reply. I do have two victron blue solar controllers.
I quickly realized I should have gotten smart controllers. Are the blue solar controllers able to interface with the GX?
The big disappointment in my setup is my controllers don't synchronize their charging.
To answer your question. I don't have enough data to definitively say if the output of the panels differ. I just turned them on yesterday. However, I'm getting 65-66 Volts from each array as it stands.
I also haven't really depleted my batteries much. I'm in testing so I'm going to leave shore power off for a while.
-
So you have all the info...
I have 2 arrays (3) 200 watt panels each.
24v battery bank (see charging specs above)
2 charge controllers 100/50 mppt
-
Thanks for the quick reply. I do have two victron blue solar controllers.
I quickly realized I should have gotten smart controllers. Are the blue solar controllers able to interface with the GX?
The big disappointment in my setup is my controllers don't synchronize their charging.
To answer your question. I don't have enough data to definitively say if the output of the panels differ. I just turned them on yesterday. However, I'm getting 65-66 Volts from each array as it stands.
I also haven't really depleted my batteries much. I'm in testing so I'm going to leave shore power off for a while.
Yes they do interface with the Venus OS GX devices you need a USB adapter cable. Your options are:
1. Color Computer CCGX (old but works, going to sell mine soon).
2. CERBO GX which is the current device, but needs external screen. Lot's of interface options.
3. Raspberry Pi 4 with Venus OS image (which I am transitioning too).
The last two options allow you to run a large OS image which integrates Node-Red into the environment. With any of these options you get access to the Victron VRM cloud and use a phone app. Read through my 1980 Prevost build thread for more info.
What BMS are you using with your batteries?
Some more reading:
https://www.victronenergy.com/media/pg/CCGX/en/dvcc---distributed-voltage-and-current-control.html (https://www.victronenergy.com/media/pg/CCGX/en/dvcc---distributed-voltage-and-current-control.html)
https://community.victronenergy.com/questions/160294/clarifying-dvcc.html (https://community.victronenergy.com/questions/160294/clarifying-dvcc.html)
-
So you have all the info...
I have 2 arrays (3) 200 watt panels each.
24v battery bank (see charging specs above)
2 charge controllers 100/50 mppt
Ok 24v times 40 amps is 960 watts maximum charging rate and you have 1200 watts of panels. Your solar controllers can handle up to 2400 watts of solar panels.
I assume they are flat mounted so at the most you might get around 1000 watts and generally more like 800-900 watts.
So unless you are interested in automation and reporting just set each controller to 25 amps and there is little chance you will damage anything.
-
A couple of YouTube channels you might like to watch are:
This channel deals mostly with the Cerberus GX:
https://www.youtube.com/@OffGridGarageAustralia (https://www.youtube.com/@OffGridGarageAustralia)
This channel deals mostly with Raspberry Pi 4 with Venus OS:
https://www.youtube.com/@tobisreallifeskillswithtobi (https://www.youtube.com/@tobisreallifeskillswithtobi)
-
I really appreciate the help.
I'm learning a lot and it sorta makes sense. I just want to stay out of trouble for now. Learning to make the system more efficient is a future goal.
I'm using SOK batteries 206 amp hours. They have an internal BMS.
What are your thoughts on that?
-
I really appreciate the help.
I'm learning a lot and it sorta makes sense. I just want to stay out of trouble for now. Learning to make the system more efficient is a future goal.
I'm using SOK batteries 206 amp hours. They have an internal BMS.
What are your thoughts on that?
I think you have to use the Victron Smart Shunt as the source of truth when using DVCC mode.
It needs a ve.Direct USB adapter https://www.amazon.com/Victron-Energy-VE-Direct-USB-Cable/dp/B01LZ6WTLW/ref=sr_1_2?crid=J4YMPDHOOLFU&keywords=victron+ve.direct+to+usb&qid=1691962832&sprefix=victron+ve.%2Caps%2C155&sr=8-2 (https://www.amazon.com/Victron-Energy-VE-Direct-USB-Cable/dp/B01LZ6WTLW/ref=sr_1_2?crid=J4YMPDHOOLFU&keywords=victron+ve.direct+to+usb&qid=1691962832&sprefix=victron+ve.%2Caps%2C155&sr=8-2) just as the smart solar controllers need.
In my case I use a USB hub to connect these cables to and then a single USB cable into my CCGX device.
-
So...I had a little glitch in the system the other day. I looked at trends stored by the BMV and discovered this (see photo).
The battery voltage must have reached the max voltage shutdown of the battery bank causing us to have a loss of power. I'm still learning so I'm not sure where to go from here.
The graph shows the same spike every day. About the time the sun starts hitting the panels in the driveway. I turned the panel breakers off and lo and behold, no voltage jump. There is an exception. I got a similar jump one late afternoon.
Is this a problem? And should the controllers be managing this? The charge voltage is set to 25 amps.
-
I did not chime in before as I'm more in line with epretot with respect to configuring Victron equipment. I swapped in a 24/3000 multiplus inverter/charger, a SmartSolar charge controller, and a Cerbo GX.
I have noticed a similar spike but have not studied to understand where it comes from. It could be the charge controller switching off for a moment but that would drive the open circuit voltage that would not pass through the system. This can be eliminated by watching for the spike once battery is full and in the evening. The other place is the inverter/charger might perform some operation but it couldn't generate voltage higher than the battery.
If the solar controller is switched off due to full charge, again, it can't pass higher voltage down the line. However, in cases where it is connected to th GX via the VE.Direct cable, it could and does send status so it could send open voltage.
I think I need one more Victron component but still assessing the need. The Multiplus is connected to the GX via VE.Direct and the SOC as those parameters are set in the inverter for calculations.
I was thinking is SOC may not be accurate as there is a dc-dc buck converter that does not flow energy through the inverter, thinking the SOC would miss this discharge from the dc-dc device, and be inaccurate. Then I thought the inverter could calculate SOC using voltage but that is faulty thinking. At present, I have not pressed the buy button for a SmartShunt placed right on the battery terminal line to ensure all drain from anywhere is captured and reported to the system, thus ensuring an accurate SOC value.
-
The voltage spike and subsequent DC disconnect is due to the BMS high voltage cutoff. If you are charging to 29.2 that is most likely the high voltage protection limit of the BMS. With LifePo4 charging to 3.65v per cell is not necessary, and actually advised against. For a 24 volt system I would set the absorption voltage to 28.4 -28.6, float at 27.4 -27.6. Shunt settings should be charged voltage .1 to .2 volts below the absorption setting with a tail current 2% - 3%, peukert 1.01, charge efficiency 99% and charge detection time of 3 min.
If you are using 2 12v batteries in series, you need a balancer between the 2 series batteries. Contrary to what many people believe, lifepo4 batteries WILL get out of balance in series strings, especially if they reach high voltage cutoff.
-
I see the same thing and have no Victron BMS. I do have a Victron charge controller that might cause this too. I will report back after studying it bit more.
I need to adjust 28.0 on charge cutoff (3.5* 8) , maybe even less. It does settle down once it cuts the solar to about 26.5-27 and stays there for the duration (3.3* 8)
Do you have a GX device? I've not had the time to dig into the logging and reporting. I'd bet the answer is found there as to what was going on during those spikes.
-
I see the same thing and have no Victron BMS. I do have a Victron charge controller that might cause this too. I will report back after studying it bit more.
I need to adjust 28.0 on charge cutoff (3.5* 8) , maybe even less. It does settle down once it cuts the solar to about 26.5-27 and stays there for the duration (3.3* 8)
Do you have a GX device? I've not had the time to dig into the logging and reporting. I'd bet the answer is found there as to what was going on during those spikes.
I do not have a GX...
-
The voltage spike and subsequent DC disconnect is due to the BMS high voltage cutoff. If you are charging to 29.2 that is most likely the high voltage protection limit of the BMS.
This was in fact the case. I changed multiple settings after reading through your reply and some additional research.
With that said. I set the Absorption to 28.8. The minimum recommended Absorption by SOK suggests 14.4 (x2).
However, I am still getting a glitch every morning. No complete power failure but glitches.
-
This was in fact the case. I changed multiple settings after reading through your reply and some additional research.
With that said. I set the Absorption to 28.8. The minimum recommended Absorption by SOK suggests 14.4 (x2).
However, I am still getting a glitch every morning. No complete power failure but glitches.
Most likely the cells are not balanced. I would set the absorption and float voltages both to 28.4 for a few days. Holding the batteries at a higher float voltage for a few days will give the internal balancer an opportunity to do it's job. Most likely the BMS's have passive balancers which are fairly low current and usually only work near the absorption level.
Edit to add: I just went back and reread your original post. You say you are running 12v batteries in series/parallel. You really need to have a balancer between the series connected batteries. Unlike lead acid batteries, lifepo4 batteries can and will get out of balance when in series. Victron makes a nice little 1 amp automatic balancer just for this purpose.
https://www.victronenergy.com/batteries/battery-balancer
-
Most likely the cells are not balanced. I would set the absorption and float voltages both to 28.4 for a few days. Holding the batteries at a higher float voltage for a few days will give the internal balancer an opportunity to do it's job. Most likely the BMS's have passive balancers which are fairly low current and usually only work near the absorption level.
Edit to add: I just went back and reread your original post. You say you are running 12v batteries in series/parallel. You really need to have a balancer between the series connected batteries. Unlike lead acid batteries, lifepo4 batteries can and will get out of balance when in series. Victron makes a nice little 1 amp automatic balancer just for this purpose.
https://www.victronenergy.com/batteries/battery-balancer
Yes. You mentioned that in a previous post. Makes sense.
Also, I'm not certain I understand what causes the jump. Or a better way of saying it is...I don't understand why the jump is an effect of unbalanced cells.
Still lots to learn.
I should also mention, the glitch is on the AC side and always corresponds with the spike. Specifically right at the start. Then everything normalizes despite the increased voltage for two or three hours.
The give away is the dehumidifier quits and the oven chimes when the clock powers back on. But once powered back on they behave normally.
-
Yes. You mentioned that in a previous post. Makes sense.
Also, I'm not certain I understand what causes the jump. Or a better way of saying it is...I don't understand why the jump is an effect of unbalanced cells.
Still lots to learn.
I should also mention, the glitch is on the AC side and always corresponds with the spike. Specifically right at the start. Then everything normalizes despite the increased voltage for two or three hours.
The give away is the dehumidifier quits and the oven chimes when the clock powers back on. But once powered back on they behave normally.
The jump in voltage is usually caused by the BMS disconnecting the battery momentarily, which is usually caused by either a high bank voltage, or a cell imbalance. If cells are not balanced, then a cell can reach the high cell voltage protection cutoff limit (usually 3.65 volts) before the overall pack high voltage limit is reached. For example, if cell #1 (it can be any cell, I just picked #1 as an example) reaches 3.65v but the remaining cells are all 3.60, the over all pack voltage for a 12v battery is going to be 14.45v which is below the pack over voltage protection of 14.6v, but the BMS will disconnect because of the single cell protection limit of 3.65.
In your case, you are series connecting two 12v batteries to achieve 24v nominal bank. In this case you could have either a cell imbalance or a series imbalance. Say you have a voltage difference of .2 volts between the upper and lower batteries in the series connection. The maximum allowed voltage for the series connected batteries is going to be 29.2v, but with a difference of .2v between the series connected batteries once you reach 29v you will actually have one battery @ 14.4v and the other at 14.6v. Then the 14.6v battery disconnects because of the over voltage protection. Over time series connected lifepo4 batteries WILL get out of balance, especially if they are being charged at or near the maximum charge voltage.
-
The jump in voltage is usually caused by the BMS disconnecting the battery momentarily, which is usually caused by either a high bank voltage, or a cell imbalance. If cells are not balanced, then a cell can reach the high cell voltage
Ok. That all makes sense to me.
Follow-up question...why is this causing a problem when on shore power as well? Makes sense if I was inverting...but not on shore.
Even on shore power, I see the effect. Again, the time stamp on the graph always matches the time of the glitch.
-
Also, is this image the correct installation of the balancer? Seems as though multiple balancers would need to be installed between each series.
-
The battery balancer will be delivered today. I'll install it this week.
This is a snapshot of what occurred this morning. This is the highest voltage jump yet. Complete power loss on the AC side.
No interruption on the DC side. I don't understand that.
This is the 3rd day of having the absorption voltage and float voltage set to the same voltage (28.80)
-
The battery balancer will be delivered today. I'll install it this week.
This is a snapshot of what occurred this morning. This is the highest voltage jump yet. Complete power loss on the AC side.
No interruption on the DC side. I don't understand that.
This is the 3rd day of having the absorption voltage and float voltage set to the same voltage (28.80)
You appear to still be having high voltage disconnects. As I said before you most likely have an imbalance between the series connected batteries. In order to be able to use a single balancer with series/paralleled batteries, you have two options. 1) you will need to connect the batteries into two parallel groups and then have a single series connection. 2) you can retain multiple series strings but you will need to connect all the midpoints together. The manual for the balancer will have a diagram.
-
Before I post anything with regards to voltage data...
Am I right to assume the data I'm collecting is trash if I have a battery imbalance?
-
Before I post anything with regards to voltage data...
Am I right to assume the data I'm collecting is trash if I have a battery imbalance?
No a voltage imbalance can take months to accumulate depending on your usage patterns.
Given a LITHIUM LIFEPO4 type battery checking it once a month should be adequate. When you detect a difference through a regular battery charger on the lowest battery.
You might want the balancer if you have very large bank or will be leaving it untended for extended lengths of time.
Obviously a single BMS to manage the entire pack is best. But hey the qualifier (your mileage may vary) still applies.
-
When comparing the voltage using the BMV 712 to one my charge controllers, this is the result (see image).
My charge controller max voltage is near or exceeds the battery disconnect despite having the absorption set to 28.80.
It's my understanding the BMV uses a certain amount of time to calculate the voltage. As a result it isn't capturing the higher voltage seen by the controller.
This tells me two things.
1. The charge controller is eventually regulating the charge down to the absorption setting of 28.80. This is why the bmv doesn't report voltage over 28.80
2. The charge controller is unable to manage the voltage once the sun is up for a small window of time. About 9am... This is causing voltage spikes and disconnecting the batteries. After about 10 minutes of intermittent power problems, everything works fine.
I thought the controller is supposed to regulate the voltage to the absorption setting.
-
When comparing the voltage using the BMV 712 to one my charge controllers, this is the result (see image).
My charge controller max voltage is near or exceeds the battery disconnect despite having the absorption set to 28.80.
It's my understanding the BMV uses a certain amount of time to calculate the voltage. As a result it isn't capturing the higher voltage seen by the controller.
This tells me two things.
1. The charge controller is eventually regulating the charge down to the absorption setting of 28.80. This is why the bmv doesn't report voltage over 28.80
2. The charge controller is unable to manage the voltage once the sun is up for a small window of time. About 9am... This is causing voltage spikes and disconnecting the batteries. After about 10 minutes of intermittent power problems, everything works fine.
I thought the controller is supposed to regulate the voltage to the absorption setting.
If you are talking Victron equipment that the phone app allows you to configure via Bluetooth. It has a bunch of different battery profiles and custom settings. Are you using lead-acid setting with LiFePO4 type battery? It does have a battery profile for LiFePO4...
-
If you are talking Victron equipment that the phone app allows you to configure via Bluetooth. It has a bunch of different battery profiles and custom settings. Are you using lead-acid setting with LiFePO4 type battery? It does have a battery profile for LiFePO4...
It's definitely configured for LiFePO4.
-
In my scan of the posts; I think the latest is that there is no DC power interruption, but the AC power drops offline?
You haven't mention what inverter that you are using?
Are you by any chance running the inverter in power save mode? If so try turning it off. The power save mode differs drastically between manufactures and is basically for older dumb appliances like filament light bulbs/resistive heaters, etc. I remember one basically put 12V DC into a 120V outlet and as soon as it gets drawn down kicks into gear with AC power.
All inverters have idle power consumption so when the sun comes up it would normally be working on replenishing the overnight battery draw down, not bumping into high DC voltage situation that you seem to have.
You might also try doing a custom battery profile on the solar charge controllers and setting the values to like 27 volts for the solar charge controllers.
I am contemplating a Node-Red automation flow in my bus, where it turns off the inverter if solar production is under 200 watts unless the TV is on. Then the next morning turn it back on when solar production passes 100 watts. Given my network hardware, IOT devices and automation computers there is always a small deficit to make up so it will always draw some power as soon as the panels can produce it.
-
I have a 24v 5000 watt quattro.
Power save is not enabled. Although I would like to explore that more.
When the panels are turned off I don't experience any issues. Or if it's overcast.
Bright mornings are the issue.
And looking at the history of the controllers, it appears they aren't regulating the voltage quickly enough.
Could be
1. A fluke
2. Bad charge controller
3. Something like loose connection.
Truth is, I don't know enough to help myself
The balancer came and I will install that.
-
i saw this and it seems similar to your situation. I did reread this thread and don't have any new thoughts on the matter.
https://diysolarforum.com/threads/mysterious-battery-voltage-spikes.69989/
-
i saw this and it seems similar to your situation. I did reread this thread and don't have any new thoughts on the matter.
https://diysolarforum.com/threads/mysterious-battery-voltage-spikes.69989/
Thanks. I read through that and did learn a bit more.
I suppose the imbalance really has a major affect on the system.
I'm going to see that solution through before exploring anything else. It makes sense that the problem is occurring more often as the batteries get further out of balance.
In other words, installing the balancer and letting it work its magic.
-
Not sure what battery config you have but in general good lithium batteries shouldn't get out of balance but a very small amount. Not sure how much a balancer is but I'd just top balance each first and see if the problem exists. If it still occurs then paying for more electronics won't fix it
-
Well since you have mostly Victron equipment you can try their forum...
In the Victron App does both the Solar controller and Quatro show the same battery voltage?
I had a problem with my system last year and the ground connection was corroded for my solar chargers..
-
Well since you have mostly Victron equipment you can try their forum...
In the Victron App does both the Solar controller and Quatro show the same battery voltage?
I had a problem with my system last year and the ground connection was corroded for my solar chargers..
Yes. I'm a member there. My thread was buried on page 4 in under an hour...
I was able to put a volt meter on the charge controller this morning during the glitch. I had 65-70 Volts coming in from each array and the battery voltage was between 28.6 and 30. Bounced up and down for a few minutes then rested at 28.80.
The quattro is consistent with what the BMV is reporting.
-
Yes. I'm a member there. My thread was buried on page 4 in under an hour...
I was able to put a volt meter on the charge controller this morning during the glitch. I had 65-70 Volts coming in from each array and the battery voltage was between 28.6 and 30. Bounced up and down for a few minutes then rested at 28.80.
The quattro is consistent with what the BMV is reporting.
Weird, how about selecting custom battery in the charge controller's setting and set the maximum voltage to say 27.5?
Then if it exceeds that you have a defective charge controller. You said arrays so I assume you have two controllers?
I recently converted my system to Rpi 4/Venus OS controller and now have a surplus CCGX device that I will be selling, you could then implement DVCC which would bring the charge controllers under automatic external control.
Going to post on my build thread about that implementation soon.
-
I believe the controllers are technically doing their job.
There are some pretty strong opinions about the battery imbalance causing this.
I did find one thread that mentioned something about the their controller needing time to adjust to early morning light. They would get an over-voltage first thing until the controller "regulated".
With regards to the CCGX, I need to watch those channels you posted. It's on the list.
I haven't added much to my build thread, but I have been so busy working on it I haven't had time to explore more solar knowledge.
-
Update:
I charged each battery individually and installed the victron battery balancer.
I've gone nearly a week without a voltage spike. I also installed the secondary monitor of the smart shunt to monitor midpoint voltage deviation.
Seems as though it was the fix.
-
Update:
I charged each battery individually and installed the victron battery balancer.
I've gone nearly a week without a voltage spike. I also installed the secondary monitor of the smart shunt to monitor midpoint voltage deviation.
Seems as though it was the fix.
The problem was out of balance batteries? Had you not top balanced them before?
-
Update:
I charged each battery individually and installed the victron battery balancer.
I've gone nearly a week without a voltage spike. I also installed the secondary monitor of the smart shunt to monitor midpoint voltage deviation.
Seems as though it was the fix.
Great to hear that you tracked down the problem and fixed it!!!
-
@ Windtrader
It appears that was indeed the problem.
No, I didn't. But lesson learned.
What I did do was check their voltages. They were close. I assumed that was good enough. Clearly it was not.
Great to hear that you tracked down the problem and fixed it!!!
Thanks. I'm amazed at how a small deviation csn cause so many issues. I guess that's the "nature" of these batteries.
-
So after installing the battery balancer, I now get a deviation alaem in the morning as the sun hits the panel.
I originally got a voltage spike and disconnect at this time of the morning.
I have also noticed this all occurs at a 100% SOC. If shore power is off, and the batteries are paetially discharged, none of these issues occur.
At least that's my observation.
I'm wondering if one of the charge controllers is the culprit.
-
So after installing the battery balancer, I now get a deviation alaem in the morning as the sun hits the panel.
I originally got a voltage spike and disconnect at this time of the morning.
I have also noticed this all occurs at a 100% SOC. If shore power is off, and the batteries are paetially discharged, none of these issues occur.
At least that's my observation.
I'm wondering if one of the charge controllers is the culprit.
Well this still sounds strange!!!!
But what batteries are you using? Are they bluetooth and can they have their firmware updated?
Maybe disable one of the charge controllers to find out which one is causing the problem.
Load a custom profile into both charge controllers that limit the maximum voltage it will charge too and back off a volt.
Get a GX computer and implement DVCC that way it will always control charging.
Leave something on like a refrigerator so it is always working from a deficit in the morning when the sun comes up.
-
The saga continues...
Here is a screen shot of my mid point deviation. It's jumping all over the place.
It is extremely cold here and the deviation became worse as it got colder.
What's weird is (and you can see by the graph) the deviation can go from .10 to 2 or 3 and back again in a moment. In fact, the voltage bounces around every second. How can that be?
I haven't tested it with a meter yet, but when the arctic blast leaves I will.
Any thoughts?