Growatt -> SOK Battery issues

[Y2JB]

Hi All,

I have a Growatt 5000ES which I have been running with a SOK 48V server rack battery (5kwh) quite happily for 6 months. I recently added a second identical SOK battery and i am now seeing some issues.

The batteries seem to sync up and communicate ok. They charge and discharge together although the state of charge can differ by over 10% at times. The problem arises when I charge my vehicle and it discharges the batteries all the way down to cut off and then utility takes over (a common usecase for me and one that has worked just fine in the past).

I have my growatt set up to stop using battery at 20% (and begin using again after solar charges back to 30%). Since i paralleled the two batteries everything looks ok as the batteries drain until the batteries hit around 30% charge and then they instantly both fall to 0% and alarms start triggering on both the battery and the inverter.

I did not make any changes to the growatt config when i installed the second battery. It is set to LI and program 52 (which is what the lady at SOK told me to set when i bought the first battery)

What's going on here?

 

[sunshine_eggo]

New batteries of any brand are subject to:

1) cell imbalance that results in premature charge and discharge termination.
2) BMS SoC reporting incorrect until balanced.

The master battery is aggregating a combined SoC between the two. If either battery hits a limit, that overrides any averaging. If either battery hits LVD or HVD, then SoC goes to 0% and 100%, respectively.

Continued cycling should see improvement.

Provided you have the power to attain full charge via PV:
Disconnect all comm cables
Set 05 to USE
Set 12 to 48.1
Set 13 to 55.2
Set 19 to 55.2
Set 20 to 55.1
Set 21 to 48

Let it run that way for a week. Restore configuration and assess performance.

Unfortunately, if you're reliant on AC charging, the Growatt AC charger doesn't do absorption. It charges to voltage in setting 13 and stop. It will be very difficult to attain balance unless you have sufficient PV to hold 55.1-55.2V for at least a few hours/day.

@timselectric can confirm/supplement/correct the above as I believe he has this model.

 

[timselectric]

Agree with all.
Except that I would disconnect comms for ever.
Life got so much simpler after I did.

 

[Y2JB]

Disconnect comms between battery AND between inverter?

 

[sunshine_eggo]

Disconnect comms between battery AND between inverter?

Disconnect all comm cables

Bolded for emphasis

 

[Crowz]

Another thing I notice on some of the discharge imbalances is how they are wired. I'm a firm believer in a common bus bar point before the inverter or charger and the batteries. It's the only way I was able to solve problems with my lead acid banks back in the day.

 

[timselectric]

Disconnect comms between battery AND between inverter?

Between batteries and inverter. And Between batteries.
Avoid disconnecting comms with this forum. lol

 

[Y2JB]

New batteries of any brand are subject to:

1) cell imbalance that results in premature charge and discharge termination.
2) BMS SoC reporting incorrect until balanced.

The master battery is aggregating a combined SoC between the two. If either battery hits a limit, that overrides any averaging. If either battery hits LVD or HVD, then SoC goes to 0% and 100%, respectively.

Continued cycling should see improvement.

Provided you have the power to attain full charge via PV:
Disconnect all comm cables
Set 05 to USE
Set 12 to 48.1
Set 13 to 55.2
Set 19 to 55.2
Set 20 to 55.1
Set 21 to 48

Let it run that way for a week. Restore configuration and assess performance.

Unfortunately, if you're reliant on AC charging, the Growatt AC charger doesn't do absorption. It charges to voltage in setting 13 and stop. It will be very difficult to attain balance unless you have sufficient PV to hold 55.1-55.2V for at least a few hours/day.

@timselectric can confirm/supplement/correct the above as I believe he has this model.

I have set this up and my PV should get the batteries charged over the next few days.

Couple of questions:

Just so I understand, you’re suggesting I get both batteries charged to full then have PV hold them at 100% for a week?

Would it speed up the process if I charge with AC to full then have PV hold it there afterward?