Question for the solar guys

[thomasinnv]

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

[epretot]

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.

[thomasinnv]

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.

[epretot]

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.

[epretot]

Also, is this image the correct installation of the balancer? Seems as though multiple balancers would need to be installed between each series.

[epretot]

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)

[thomasinnv]

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.

[epretot]

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?

[freds]

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.
 

[epretot]

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.

[freds]

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...

[epretot]

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.

[freds]

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.

[epretot]

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.

[windtrader]

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/