FB21 using battery with grid but no PV

[mciholas]

I just got an FB21 installed. It runs in Backup mode where I want the batteries to only be used if grid is down and PV is inadequate.

At night, with no PV input, but with grid, it draws about 1.5 amps from the battery. This is not reported anywhere on the EG4 monitor app, it was measured with a clamp meter. I measure about 0.75 amps per battery (two wall mounts). If I turn off one battery, the other rises to 1.5 amps, so this is a real measurement on a properly zeroed meter. During this time, the grid current is basically zero or near it. If I turn off both batteries, the grid current picks up to about 0.2 amps, and I get the yellow LED.

During no PV times, I get constant green LED slow flashing. The manual doesn't say what that means. I get steady green during PV power and fast flashing green during firmware updates.

I've tried to go through all the configuration parameters and I can't find anything that seems like it would control this, and I have tried changing some of them with no luck.

Let me know if you have any useful insights or things to check. I'd really like to not have the batteries clipped every night when grid is available.

Mike C.

 

[Tommytwotone]

You have idle consumption for the FB 21. Is that what you are seeing?

The yellow is a fault. You would see a notice in the portal (eg4 monitor0 when that occurs.

I am in self consumption and will have to look if the green light on the Flexboss changes. I sort of think it just stayed solid.

 

[mciholas]

You have idle consumption for the FB 21. Is that what you are seeing?

Yes, but it draws it from the battery instead of the grid. That is bad behavior, I don't want it drawing down the battery when the grid is available, that's just needless battery cycling for a net metering setup.

The yellow is a fault. You would see a notice in the portal (eg4 monitor0 when that occurs.

Yes, I do, when both batteries are off, as expected.

What I don't know is what slow flashing green means. The manual does not say. The unit is solid green when there is PV input, flashing green when no PV input. What does the slow green flash mean?

I am in self consumption and will have to look if the green light on the Flexboss changes. I sort of think it just stayed solid.

Let me know.

Mike C.

 

[Tommytwotone]

Yes, but it draws it from the battery instead of the grid. That is bad behavior, I don't want it drawing down the battery when the grid is available, that's just needless battery cycling for a net metering setup.


Yes, I do, when both batteries are off, as expected.

What I don't know is what slow flashing green means. The manual does not say. The unit is solid green when there is PV input, flashing green when no PV input. What does the slow green flash mean?


Let me know.

Mike C.

I will look tonight when pv is gone and let you know.

 

[mciholas]

Another thing:



What is wrong with that picture? Both batteries report 99% on their front display, but the voltage reading above, the voltage reading on the battery displays, and the actual voltmeter reading agree, 46.6 volts.

There's no way the batteries are 99% charged.

What is going on here?

Batteries are communicating via CAN to the inverter. Maybe I should switch it to RS495 port instead?

Also, SA reports battery temp as 2 C, but cell temps as 28 to 30 C. Something is off there, too.

Maybe the battery heater is on by mistake?

Confused.

Mike C.

 

[42OhmsPA]

What is going on here?

A load below ~1.5A is pulling from the battery bank, the BMS doesn't register it, SoC gets out of whack. Closed loop, SNAFU.

 

[Quattrohead]

You need to get those batteries charged, they are all but dead.
Just confirm that that 46 volts is real and let the batteries charge to at least 55 volts and held there for an hour to get them balanced up and the BMS recalibrated.
Do you have the inverter set to off grid mode? In this mode it will not touch the grid unless it absolutely has to for overload reasons so it will not ever pull power from the grid. If it knew the actual SOC right now it would be pulling from grid to recharge those batteries.

 

[mciholas]

Inverter not in off grid mode.

I put the system in volt mode instead of SOC and now charging, but slowly, 20 A per battery being limited by the BMS. So it will take a while to get them back to shape.



I surmise the BMS will recalibrate this after a while, but it will take probably overnight and AC charging to get it done. I should probably top it off at 3.6 V/cell, 57.6 volts, and let it sit there a while to get the balancing time to work.

The voltage is real, voltmeter measured.

The batteries are not routinely use, they are there for grid down purposes only, and they have been doing that for 4 months. With a voltage controlled charge, they wouldn't sag like that and get top charged periodically.

In theory, BMS comms should result in a better experience, but that hasn't been the case for me whereas voltage mode seems far more reliable and predictable. So I'm going to go voltage mode and set conservative upper and lower limits.

Mike C.

 

[Tommytwotone]

Another thing:

View attachment 292858

What is wrong with that picture? Both batteries report 99% on their front display, but the voltage reading above, the voltage reading on the battery displays, and the actual voltmeter reading agree, 46.6 volts.

There's no way the batteries are 99% charged.

What is going on here?

Batteries are communicating via CAN to the inverter. Maybe I should switch it to RS495 port instead?

Also, SA reports battery temp as 2 C, but cell temps as 28 to 30 C. Something is off there, too.

Maybe the battery heater is on by mistake?

Confused.

Mike

Yes, but it draws it from the battery instead of the grid. That is bad behavior, I don't want it drawing down the battery when the grid is available, that's just needless battery cycling for a net metering setup.


Yes, I do, when both batteries are off, as expected.

What I don't know is what slow flashing green means. The manual does not say. The unit is solid green when there is PV input, flashing green when no PV input. What does the slow green flash mean?


Let me know.

Mike C.

I only have a solid light. I have mine in self consumption mode with net metering but I had it off grid before and it was solid then as well.