SPF3000TL LVM-ES

[bruno_cmenezes]

I'm experiencing this inconvenient situation with an offgrid system that comprises four inverters of the model SPF3000TL LVM-ES in a split-phase configuration. The AC input is a 40kW diesel generator and there are 32 lead-acid 220Ah batteries to supply the loads (8 groups of 4 batteries in series). The system supplies the loads in 2 phases (220V/127V), which means that each phase is connected in two inverters.

The problem is that the generator is never able to charge the batteries when it starts. The two settable programs that are related to the generator functioning are the program 12 and the 13 in the installation manual, as it follows:


Sometimes, at night, when there is a more intensive use of the loads and the batteries voltage drops to the value set in program 12 (48 V), the inverter closes the dry contact connected to the generator, making the generator start. As soon as it starts, the voltage increases again to something around 50V, which is a natural behavior since the current flows in the opposite direction. What is curious is that the inverter opens the dry contact (turns off the utility) again without the batteries being able to reach the voltage set in program 13 (54V), and, as a consequence, it does not charge batteries at all, causing the system to drop the voltage once more below 48V, bringing back the utility again. In my understanding, the program 13 is not working in any circunstance, i do not know if it is a algorithm problem or a setting problem.

The picture below shows this behavior:



Does anyone know how i can fix this?

 

[sunshine_eggo]

These are notoriously picky about generator input.

Try lowering your utility charge current to 50% of the current value and see if it improves.

 

[bruno_cmenezes]

@sunshine_eggo Could you explain how this change would impact system's functioning? I mean, i am aware that charge current has to do with the charging time, but the batteries actually do not charge at all, it seems that only the program 12 is able to control if utility turns on or off. If voltage is below 48V, the generator starts, if it is above 48V, it turns off. I tried doing a test that proves my point:
I powered as many loads as i could to discharge the batteries and trigger the generator. When it started, I increased the program 12 voltage to 51V and it really charged the bank to the voltage set. When the voltage reached this value, the generator turned off.

I don't see how the charge current can affect that, that's why I asked you for an explanation (I wont't rule out this possibility, in fact I want to try it later). Have you ever been in a situation like this before?

 

[sunshine_eggo]

Are you in SOL or SBU priority?

@sunshine_eggo Could you explain how this change would impact system's functioning? I mean, i am aware that charge current has to do with the charging time, but the batteries actually do not charge at all, it seems that only the program 12 is able to control if utility turns on or off. If voltage is below 48V, the generator starts, if it is above 48V, it turns off.

You said 50V before.

I tried doing a test that proves my point:
I powered as many loads as i could to discharge the batteries and trigger the generator. When it started, I increased the program 12 voltage to 51V and it really charged the bank to the voltage set. When the voltage reached this value, the generator turned off.

I don't see how the charge current can affect that, that's why I asked you for an explanation (I wont't rule out this possibility, in fact I want to try it later). Have you ever been in a situation like this before?

Per my above comment, these things are picky about charging from generators. Reducing the charge current makes them more tolerant of charging from generators.

 

[bruno_cmenezes]

Are you in SOL or SBU priority?

This happens in both priority settings. At first I was in SBU, and then I changed it to SOL but it keeps behaving like that.

You said 50V before.

The system reaches 50V only because of the voltage drop due to batteries internal resistance.

 

[sunshine_eggo]

These are notoriously picky about generator input.

Try lowering your utility charge current to 50% of the current value and see if it improves.

@bruno_cmenezes

Have you tried this?

 

[schmism]

what are your 12, 13, and 21 settings.

you should be able to make this work if you spread your settings out enough. (it sounds like your on FLA batts)

 

[bruno_cmenezes]

@bruno_cmenezes

Have you tried this?

I set the maximum charging current to 60A and the AC charging current to 20A (it was 30A before). I'll keep monitoring to see if it works.

 

[sunshine_eggo]

I set the maximum charging current to 60A and the AC charging current to 20A (it was 30A before). I'll keep monitoring to see if it works.

I understand it's not desirable at all, but try as low as 10A if 20A doesn't work. I presume this needs to be changed on all 4 inverters, too.

 

[bruno_cmenezes]

what are your 12, 13, and 21 settings.

you should be able to make this work if you spread your settings out enough. (it sounds like your on FLA batts)

Program 12: 54V
Program 13: 48V
Program 21: 44V

My batteries setting is on user defined, as Growatt told me to do.

 

[bruno_cmenezes]

I understand it's not desirable at all, but try as low as 10A if 20A doesn't work. I presume this needs to be changed on all 4 inverters, too.

I've just set to 60A/10A, I'll see what happens.