Growatt SPF5000ES 2x Parallel + Overkill BMS Overcharging Issue

[wheatman]

Hey guys!

I've assembled the following config for my neighbour:

2x Growatt SPF5000ES invertors connected in parallel
280Ah battery bank DIY (16x cells) with a 100A 48v OverkillSolar BMS
2 equal Arrays x 7pcs of 660w Canadian Solar in series, each array coming into each invertor separately (14pcs in total)
Equal cable length to the battery from both invertors
The settings are as follows:
Battery Type USE
CV 56.4
FLV 54.4
CO 42.8

The system is working fine, the invertors are in slave/master modes as it should be, but i keep randomly getting the 03 fault with a long continious beep from them from time to time, followed by the electricity going off. Usually it happens when there's a lot of sun, and especially when after some load - like, everything is working fine, I use a circular saw, and 10-15 mins AFTER this the invertors go fault mode. I assume there is some kind of miscommunication between the BMS and the invertors, but dont have enough experience to know where to start from.

Also, I use a similar setup at my home, but with one Growatt invertor, 4 panels the same kind and 2 of 280ah batteries with same BMS, and have never had this kind of problem. Will appreciate your input a lot, its a pain to manually restart the invertors each time after the fault Here are some pics of the neighbors setup as well:

 

[sunshine_eggo]

The system is working fine, the invertors are in slave/master modes as it should be, but i keep randomly getting the 04 fault from them from time to time. Usually it happens when there's a lot of sun, and especially when after some load - like, everything is working fine, I use a circular saw, and 10-15 mins AFTER this the invertors go fault mode. I assume there is some kind of miscommunication between the BMS and the invertors, but dont have enough experience to know where to start from.

This is not possible. You are in USE mode with ensures there is no BMS communication.

Step 1 when weird shit is happening is to check ALL connections for quality and torque - every single one of them - both current carrying conductors and BMS sense leads.

 

[timselectric]

04 is battery voltage too low.
Not enough battery capacity.
400ah is recommended for 2 units.

 

[wheatman]

sorry my bad - it is 03 fault with a long continuous beep, edited the initial post as well

 

[sunshine_eggo]

Lower absorption to 55.2
Raise float to 55.1

Likely BMS triggering overvoltage due to cell imbalance. MPPT spikes voltage before it can clamp down on current.

55.2V = 3.45V/cell, which should avoid/reduce the fault frequency. Ensure BMS is configured to begin balance at 3.40V and 20mV cell difference. Make sure balance only during charge is disabled.

Did you top balance the pack immediately before putting it into use?

EDIT: the goal with the lower absorption and higher float is to allow the system to stay at "balancing voltage" for extended periods to give the anemic balance current time to balance the cells. A 0.35% change in balance will take being held at a balancing voltage for 24 hours.

 

[Brett V]

The numbers eggo gave will work. I'm using a Growatt SPF12000T and use 55.0 / 54.0 with good results. I highly recommend Solar Assistant, it makes monitoring and controlling things much easier.

 

[wheatman]

@sunshine_eggo @Brett V Thanks for the input guys, will test the numbers you gave and report if there are any further issues.

I also thought that the lack of the initial top balancing might be the issue. The initial cells disbalance was around 0.005v, and the pack I'd assembled for my own system never gave me problems - the BMS balanced them perfectly within the first week of usage - so I decided to give it a go at the neighbour's system the same way. But i guess 2 invertors and higher amounts of power at his installation make it work in a different way. Will change the settings the way @sunshine_eggo suggested and see what's what. Appreciate this community a lot!

 

[sunshine_eggo]

@sunshine_eggo @Brett V Thanks for the input guys, will test the numbers you gave and report if there are any further issues.

I also thought that the lack of the initial top balancing might be the issue. The initial cells disbalance was around 0.005v, and the pack I'd assembled for my own system never gave me problems - the BMS balanced them perfectly within the first week of usage - so I decided to give it a go at the neighbour's system the same way. But i guess 2 invertors and higher amounts of power at his installation make it work in a different way. Will change the settings the way @sunshine_eggo suggested and see what's what. Appreciate this community a lot!

Voltage and balance are only analogous when voltage is > 3.40V. The typical 3.29-ish Volts these cells are received at tells you absolutely nothing about their SoC or "balance." I did actual as-received discharge testing and found my cells ranged from 28% to 40% SoC when they had near identical voltage. That's a HUGE difference. In other words, when the first cell hits full, my lowest cell is only at 88%. The typical balance current of a JBD/Overkill would take nearly a month of CONTINUOUS balancing above 3.40V to passively burn off 12%.

Even significantly imbalanced batteries will show nearly identical voltages in the 3.1-3.4V range under load and charge.

 

[Drsif]

@wheatman did you manage to fix the problem?

 

[Drsif]

Are you happy with the Growatts ?what about the efficiency 80%? and the fan noise ?

the price is good but do they really worth ?

 

[Drsif]

?