Growatt SPF5000ES charging peculiarities?

[rrroonn]

Hi,

I am hoping someone has experience with this issue as I am new to Growatt.

SETUP

I have set up pre-prod system to augment my existing solar setup (Victron MP2 + Pylontech ESS + 6.5kW panels).
I have 12kW of 16s (51.6V) batteries attached to Growatt SPF5000ES with no grid input and no battery-inverter comms.

I have setup the following settings:
01: SBU (solar & battery priority)
02: 80a
03: APL
05: US2 (User settings 2)
12: 48v (back to grid)
13: 51v (back to battery)
14: 050 (solar only charge)
19: 55.6v (CV charge voltage) -- setting this higher did not help
20: 54.4v (float voltage)
21: 46v (low voltage cut off)

Firmare is 040-05-70 (CPU1) 041-05-701 (SPU2)

The aim is to be gridless and use solar to charge batteries and supply loads.

THE PROBLEM
There are circumstances that I do not understand where the batteries refuse to charge off the solar panels. I have read a lot of posts that relate to this but none lead me to an answer, so I hope that someone reads this and goes "aha ..."

I have drawn down the batteries using a clothes dryer drawing 1.8kW for about an hour ...



The panels have Voc of about 160v and MPP of about 120v and we can see that they are helping to supply the load. I had the load running for an hour or so and then removed the load.


No matter how long I stared at the screen, the solar charger refused to now recharge the batteries. Yes, I see that the CHG LED is on but the panels remain at Voc.

Just to ensure that the start voltage of 150v+/-10 was not the problem, I added another panel...



Again, the batteries refused to recharge.

In much of my testing, the solar WAS charging the batteries, but now it isn't.

I tried switching to from US2 -> USE but this did not help. I turned the batteries off and then back on and charging started. Power cycling the inverter also restarts charging.

I have seen comments that it could be a firmware issue or a faulty unit. Is there something else that I can try?

Note: I have used the unit with and without the communications between the battery and inverter - in both cases it WAS charging. I don't want to use it in mode 5 (LI).

Thank you for you attention.

Ron

 

[octal_ip]

This is likely due to the weird charging algorithm that Growatt uses. It usually comes down to constant voltage and float voltage charge settings (19 and 20). What are they currently set at?
I experienced the exact same problem, and have resolved it by setting CV to 55.5 and float to 55.

 

[rrroonn]

I will provide an update.

Firstly, the problem does appear to be the algorithms built in to the inverter. Rather than floating at a set voltage (when using USE2), the charger seems to turn itself off and requires some propietary set of circumstances (time, voltage etc) to decide to turn on again. In the end, I ended up using USE mode (IE like a lead acid battery) and turning equalisation off. This seems to work predictably.

Secondly, I tried to get support from Growatt Australia but this was frustrating and ultimately useless - think carefully before buying this brand.

Also, of note, is that the inverter consumes quite a bit of power just doing nothing. Overnight, with nothing connected to AC, it will consume more than 10AH (@54V). Enough for a small fridge! This could be a problem depending on your circumstances.

 

[octal_ip]

Since my last post I've started using 55v for CV and 54.5v for float on USE. Despite only being 0.5v less than my previous settings, the actual charging profile has changed quite a bit, with the Growatt now only starting to charge once the battery drops below 52.5v. This means some days the battery doesn't even start charging, though I've come to appreciate this because it only happens if I've not used much battery capacity at all. This means less stress on the cells by reducing the amount of time they're sitting at a very high state of charge. The charger kicks in as soon as that 52.5v threshold is met, and solar will always provide as much power as it can to the loads before any battery energy is used.

I'll go back up to 55.5 CV/55 float if I ever need a guaranteed daily full charge, though given the cells are the most costly component of the whole system, I prefer to teat them gently for now.

Secondly, I tried to get support from Growatt Australia but this was frustrating and ultimately useless - think carefully before buying this brand.

You're not alone. They've developed a reputation for having customer support so poor that it might as well not exist. At this stage I'm not even sure they'd honor a legitimate warranty claim.

Also, of note, is that the inverter consumes quite a bit of power just doing nothing. Overnight, with nothing connected to AC, it will consume more than 10AH (@54V). Enough for a small fridge! This could be a problem depending on your circumstances.

Yes, pretty much all the "all-in-one" inverters (and indeed some dedicated inverters) have this problem. I've worked around it with my custom firmware that allows me to remotely switch the inverter off when I don't need it. Otherwise it's an overhead you just have to accept.

 

[rrroonn]

Yes, pretty much all the "all-in-one" inverters (and indeed some dedicated inverters) have this problem. I've worked around it with my custom firmware that allows me to remotely switch the inverter off when I don't need it. Otherwise it's an overhead you just have to accept.

Interesting - I see your code uses the modbus interface that I already use directly via RS485 (and Node Red & Home Assistant)...The doco I have shows holding addr 0 is not writable but your code uses that ... I have just tested directly via RS485 and the output control does indeed work - so thank you for the pointer.

thanks,

 

[octal_ip]

Nice work!