How to run my coffee maker on a Growatt SPF3000TL LVM without errors

[dwfjef]

I’m trying to solve errors 10 (Output power derating) and 04 (low battery) with my Growatt SPF3000TL LVM (24V system). Here’s the setup.

I’ve a concession shack with solar panels, 2 Interstate Marine/RV (Group 24DC) batteries (wired in series with 2AWG cable), Growatt SPF3000TL LVM Inverter and an AC shore power connection (300ft 12AWG cable). My problems occur when I try to use a 1500 watt coffee maker. If I’m in utility first mode as soon as the coffee maker kicks on, the line voltage drops below 95VAC and the Growatt reports warning 10 (Output power derating). That makes sense because of the 15 amp draw on the long cable causes the line voltage to drop. I was hoping that the Growatt would then kick on its inverter from the battery and boost the voltage but it doesn’t have a boost mode.

If I’m in SBU priority mode, and the coffee maker kicks in, everything is fine for a few minutes while the batteries and inverter provide the power. However, during the operation, the battery voltage is dropping quickly until it hits the 20V cutoff voltage (set by Program 21) of the Growatt at which time the Growatt either switches back to utility (which doesn’t work) or shuts down with error 04 (batteries low). The large drop in battery voltage is mostly due to the 50amp draw from the batteries and not a drop in the capacity of the batteries. They are back to 90% when the system shuts down.

Any solutions? I’ve got Program 21 set as low as it can go (20VDC). I tried a small power stabilizer on the incoming AC but the unit I had was too small (300W) to do any good – it just overloaded when the coffee maker turned on. I tried adding a 24VDC charger (10amp) to the batteries powered from shore power to help keep the battery voltage up but that didn’t help. Now I’m thinking of using a simple Full Wave Bridge Rectifier on the incoming AC and connecting its output (40 to 60 VDC) in parallel with the solar panels. That would provide the Growatt inverter with extra power to power the loads and reduce the demand from the battery.

If that doesn’t work, I'm pretty sure that a switch to LiFePO4 batteries will solve the problem? But that's expensive.

What do you think? Will the rectifier work? Any of you Growatt users have relevant experience?

Any other solutions?

 

[timselectric]

Easiest solution is more battery capacity.
Not sure if you have room for more solar panels. But, that would help too.

 

[robby]

You only have one choice and that is Larger batteries with more Ah available also a better way to charge them.

 

[dwfjef]

You only have one choice and that is Larger batteries with more Ah available also a better way to charge them.

Yes, I considered doubling the batteries (2S 2P) but I'm gun shy of lead acid batteries because of their poor performance under load. I don't want to do it and still have the same problem.

 

[dwfjef]

Easiest solution is more battery capacity.
Not sure if you have room for more solar panels. But, that would help too.

This needs to work at night too so the additional panels don't really matter. I'm thinking that the rectifier will work like extra panels day and night!

 

[timselectric]

This needs to work at night too so the additional panels don't really matter. I'm thinking that the rectifier will work like extra panels day and night!

That would require a separate charge controller. Or you can damage your solar panels. Yet, it is an interesting theory.

 

[schmism]

As you have noted the growatts do not have a boost option. It's simply an internal relay. Either grid-in--> grid out. Or the inverter on 120v out.

Id add 2 more batteries and a 24v battery charger tied to your shore power. something like 25a of 24v (only about 700w AC) your anemic extension cord might run and allow you to boost the battery output and charge them at night.

Remove the "grid" input to the growatt.

 

[timselectric]

The Growatt can charge from the grid connection.

 

[dwfjef]

That would require a separate charge controller. Or you can damage your solar panels. Yet, it is an interesting theory.

I believe the solar panels have a blocking diode to keep them from receiving power from units connected in parallel. So, I don't think my rectified AC will damage the solar panels. I think it should work with the rectified AC connected in parallel with the solar or in place of the solar.

 

[timselectric]

Not a blocking diode.
A bypass diode.

 

[timselectric]

A blocking diode stops power from moving.
A bypass diode allows power to flow around.

 

[timselectric]

Blocking diodes could be added.

 

[schmism]

The Growatt can charge from the grid connection.

You'll have to ensure that your configuration is correct.

1 - SBU
11 - 10a
12 -22.0
14 - snu
18 - byd

The concern with having the growatt charge is that at 10a (its lowest charging amount) you may still under volt due to your inadequate grid supply causeing errors on the growatt.

A "dumb" transformer based external charger likely wont care (as much)

 

[dwfjef]

You'll have to ensure that your configuration is correct.

1 - SBU
11 - 10a
12 -22.0
14 - snu
18 - byd

The concern with having the growatt charge is that at 10a (its lowest charging amount) you may still under volt due to your inadequate grid supply causeing errors on the growatt.

A "dumb" transformer based external charger likely wont care (as much)

Yes, I have those settings and see the Growatt charge the battery from AC. However the charging from AC is not enough to keep the battery voltage from sagging under load. And then when it reaches the cutoff voltage it switches to Utility power and I'm back at error 10. I think the best solutions are more/better batteries and perhaps the rectifier. I've bought a KBPC5010 Bridge Rectifier Diode (50A 1000V Single Phase,Full Wave 50 Amp 1000 Volt Electronic Silicon Diodes) and will try it next week to see how it works. I believe I'll get some increase in performance with it and then decide about doubling the batteries or changing to LiFePO4.

 

[timselectric]

I would recommend that you isolate your rectifier from the solar panels. But, it's your money to burn if you choose.
Good luck and be safe.

 

[dwfjef]

I would recommend that you isolate your rectifier from the solar panels. But, it's your money to burn if you choose.
Good luck and be safe.

By "isolate" do you mean use a "blocking diode" or are you thinking of something else?

 

[timselectric]

Not connected with each other. I'm not sure if blocking diodes will provide the necessary protection, in this situation.

 

[schmism]

I think you need to do some work on your batteries. Check their level, the SG etc. 1500w @24v = 62a Lets say they are 250? ah FLA... I would expect them to hold 62a for the 5? min the coffee maker is running without sagging that much.

without a better understanding of what your load is overnight we wont be able to size the battery for "last overnight"

 

[rcrracer]

To reduce voltage drop: 10 gauge extension cords? Plug in cords closer to service of building supplying power? Auto transformer for coffee maker. https://www.amazon.com/Mophorn-Tran...lja1JlZGlyZWN0JmRvTm90TG9nQ2xpY2s9dHJ1ZQ&th=1

 

[acdoctor]

I suspect the batteries. I don’t think they have what it takes.
Th 140 AH is probably at 100 hours.
Need to battery up or forget the inverter.


Specifications:

• Group Size: 24DC
• Part Number: 8-24MP
• Cold Cranking Amps(CCA): 550
• Cranking Amps(CA): 700 MCA
• Reserve Capacity(RC): 140
• Length: 11
• Width: 6 7/8
• Height: 9 1/2
• Weight: 41