Growatt 12K inverter charging

Bigblockcutlass123

Solar Enthusiast
Joined
May 8, 2021
Messages
111
Location
Michigan
Here are some pictures of my grow lot once it starts getting a lot of acid batteries full. Wonder what people's thoughts are.
 

Attachments

  • Screenshot_20211028-163215.jpg
    Screenshot_20211028-163215.jpg
    316.7 KB · Views: 6
  • Screenshot_20211028-163109.jpg
    Screenshot_20211028-163109.jpg
    472.5 KB · Views: 6
  • Screenshot_20211028-163016.jpg
    Screenshot_20211028-163016.jpg
    561.9 KB · Views: 6
  • Screenshot_20211028-162955.jpg
    Screenshot_20211028-162955.jpg
    446.6 KB · Views: 6

RCinFLA

Photon Sorcerer
Joined
Jun 21, 2020
Messages
1,593
It may be the result of 120 Hz ripple current which is normal from a sinewave inverter, assuming 60 Hz sinewave inverter. Its peak to peak level is a little over twice the average DC current. Voltage ripple is ripple current against battery impedance and cable losses.

Usually it is filtered out by BMS for its average reading display. The sampling rate on the BMS gives it an erratic look.
 

indalecio

New Member
Joined
Oct 26, 2021
Messages
35
You curve is very strange. Do you have a PWM charger? Where the red curve comes from?
 

Bigblockcutlass123

Solar Enthusiast
Joined
May 8, 2021
Messages
111
Location
Michigan
The large curves are from load change on the load from the inverter. Line always get flat or smooth when more power going out than coming in.
 

Bigblockcutlass123

Solar Enthusiast
Joined
May 8, 2021
Messages
111
Location
Michigan
This is a 12 k all in one inverter. It is low frequency split phase inviter with two mppt charge controllers. The only time the graph from the Victron shunt looks like this is was the Battery are getting topped off wile a load is on the inverter. If there is no load, smooth output of the chargers. If there is load and the battery voltage is down to lets say 48 volts, smooth output. If there is Load on the inviter and the voltage is like 54 56 volts, then the output is not smooth, I have seen the Victron shunt gong from 1500 watts in and 1500 out of the battery's (like the graphs shows) This does not reflect the load on the Inviter. (smooth even load on the Inviter.) If I shut off solar power to one of my built in charge controls at a time, does not stop this from happening. Both built in charge controllers do the same thing independently. if one is disconnected.
 

RCinFLA

Photon Sorcerer
Joined
Jun 21, 2020
Messages
1,593
The large curves are from load change on the load from the inverter. Line always get flat or smooth when more power going out than coming in.
On a LF inverter the internal PV charge controllers delivers their current directly to battery node. (HF inverter can dump PV to HV DC point)

If it only happens when PV power exceeds AC power loads then it must be associated with PV charge controller pumping into battery node and checking for battery voltage to regulate charge. Its chopping may be the way it regulates charge to battery, either bulk current or absorb/float voltage control. The charge controller must put up with the 120 Hz ripple current from inverter while making its charge regulation checks.

Since it appears your battery is near full charge it would be interesting to see what happens when battery state of charge is lower and can take the full PV power available. Particularly when in constant current bulk mode charging.

PV delivered current can be a constant (based on sun illumination current) where the DC supply to inverter has the 120 Hz ripple current so on an instantaneous basis, the current to battery can swap directions when inverter load 120 Hz ripple current instanteously exceeds or is less than the relatively constant PV supplied DC current.

I am surprise still, as the 120 Hz ripple current is usually filtered by a monitor to yield average DC current level. I would expect something like that waveform is you put a DC amplifier directly from current shunt sense output and looked at it on a scope.

If it is caused by a lower frequency on-off checking by PV charge controller then it could make it through the monitor's averaging filter. I would fear it might screw up the monitor's coulumb counter tally because it is happening so fast the monitor's sampling rate may not be fast enough to keep an accurate tally of input-output current.
 
Last edited:

Bigblockcutlass123

Solar Enthusiast
Joined
May 8, 2021
Messages
111
Location
Michigan
When the battery is at a lower state of charge. The graph is pretty smooth. Only when the battery starts to get full is when the graph looks like this.
Thanks for all the info.
 

RCinFLA

Photon Sorcerer
Joined
Jun 21, 2020
Messages
1,593
When the battery is at a lower state of charge. The graph is pretty smooth. Only when the battery starts to get full is when the graph looks like this.
Thanks for all the info.
Pretty much seals it. It is the SCC float/absorb voltage regulation.

Lead-acid batteries have a higher impedance so will show more voltage jump with charge/discharge current.
 
Top