Growatt ML33RTA batteries - behaviour and performance

cool_techie

Hi Forumites,

Does anyone have experience of using Growatt ML33RTA batteries?

Need to exchange thoughts about their charging/discharging performance and usage in general.

Mine are also managed a Growatt inverter (SPH-6000), which has some gremlins of its own. Thats another story though!

Would be good to have a discussion on the battery performance and if anybody has managed a 'proper' working Growatt monitoring App OR alternatives. I am currently using the flaky ShinePhone app.

Thanks,
CT

Solarchaser

Nothing to say about the batteries, I've had no dealings with them. 

Disappointed to hear growatt sph is still having gremlins, make sure you keep on at growatt, it took me over 6 months to get them to refund me.

cool_techie

Solarchaser said:

Disappointed to hear growatt sph is still having gremlins, make sure you keep on at growatt, it took me over 6 months to get them to refund me.

Hi Solarchaser,

TBH, the gremlins within SPH inverter are minor - slow switching between charge and discharge modes, Grid supply etc. The issue on the inverter side is mainly !!!!!! poor monitoring via the ShinePhone app. I am looking to get a Raspberry PI solution, if nothing else is available.

My bigger issue is, despite a 12.7 kW system, I hardly seem to go above 1.9kW at any given instant. My E-W orientation of panels + slow inverter reaction time is not helping. Also, i have realised that, a large portion of my panels, though not shaded, do not get directly sunlight 'on' them. Hence I may be looking at optimizers. TIGO has been suggested.

Discussing with the installer about how to get this sorted. They have given me an yearly performance of 10,199 kW, which may be achievable, with a surge in the summer months. Hence, they may come around as optimizers being an extra. That is going to be an interesting discussion.

My beef is, about maximising the generation using technology options, given the location/roof limitations. Also, the fact that, the panel layout was designed and installed by them. I do remember asking the sales guys about optimizers, only to be told that these being half-cell modules, they performed well even if shading was an issue and hence optimizers wont be needed. That clearly seems to be not happening now.

Today, being not a great sunny day, the overall generation has been 5.4kWh. Main reason in going for such a large system was to get a decent generation, given that it was going to be a E-W orientation. But that does not seem to be happening with the current configuartion.

For reference, I have attached, my current layout, with my current observations of the 'problem' areas. Any suggestions you guys can provide are welcome.

Thanks, CT

Solarchaser

Hi CT there's a couple of things here. 
First the sph6000 has a max pv input of 8kw, you seem to be quite a bit more than that. 
You have 2 different inverters?
Or if not, how is the mppt set, is it part of one roof facing east, and the other east facing roof on one mppt string?

The slow switching just seems to be growatt, I doubt you will improve that.

I found the phone app not too bad tbh other than it never made any sense,  the numbers never added up together and it did what it wanted.

For a random users comparison my 6.6kw array made 8.1kwh today

cool_techie

Solarchaser said:

Hi CT there's a couple of things here. 
First the sph6000 has a max pv input of 8kw, you seem to be quite a bit more than that. 
You have 2 different inverters?
Or if not, how is the mppt set, is it part of one roof facing east, and the other east facing roof on one mppt string?

The slow switching just seems to be growatt, I doubt you will improve that.

I found the phone app not too bad tbh other than it never made any sense,  the numbers never added up together and it did what it wanted.

For a random users comparison my 6.6kw array made 8.1kwh today

Ah yes, you are right.

I have two inverters, the 2nd one being Growatt MIN 6000TL-X. This is for the two strings on the garage, comprising 20 panels.

The remaining 2 strings from the 13 panels on the house roof go to the SPH-6000. I have corrected my system to include the 2nd inverter.

You are right about the ShinePhone app, the numbers never add up. Guess this is due to the 5 min sampling of the system, which cannot be reduced.

Also, in my case, the app only shows Power generation from the strings connected to the SPH-6000. But the total figure in the circle shows the combined output from the system. Results being, i do not know at any instant, how much my system is generating as whole. I have tried reconfiguring the ShineWifi-X system to go through the ShineLan Box, but with no success so far. Picture below depicts.

Btw, did you contact Growatt directly and do they have any UK number/office at all? In my case, the installers have been no good on helping on such 'good to have' matters!


Thanks, CT

Solarchaser

Ahh yeah I understand. 
So that is weird, your total with 13 x 385 panels is just over 5kw, so you should be running an sph 3000 not a sph 6000, generally you overspec panels to inverter to get the best out of it.
The sph3000 can take 6600w of panels and gives the same charge and discharge rate, yes it will limit generation to 3kw in the height of summer, but generally you would get better generation when you need it, ie winter.

I complained initially through the seller,  but he passed me onto growatt.
martin@ginverter.com was the service manager 
scott.feng@ginverter.com was the UK engineer I think.

ben.h@growatt.com I think this guy made things happen,  but not sure.

Worth pinging them an email at least, make sure and include full model number and serial number, and expect stupid questions and dodgy answers.

Gotta be honest CT if it was me, I'd have took the west facing ones on the house and put them south facing, you have as much room with that dormer as you do with the west... or that's how it looks on the photo.

cool_techie

Solarchaser said:

Ahh yeah I understand. 
So that is weird, your total with 13 x 385 panels is just over 5kw, so you should be running an sph 3000 not a sph 6000, generally you overspec panels to inverter to get the best out of it.
The sph3000 can take 6600w of panels and gives the same charge and discharge rate, yes it will limit generation to 3kw in the height of summer, but generally you would get better generation when you need it, ie winter.

I complained initially through the seller,  but he passed me onto growatt.
martin@ginverter.com was the service manager 
scott.feng@ginverter.com was the UK engineer I think.

ben.h@growatt.com I think this guy made things happen,  but not sure.

Worth pinging them an email at least, make sure and include full model number and serial number, and expect stupid questions and dodgy answers.

Gotta be honest CT if it was me, I'd have took the west facing ones on the house and put them south facing, you have as much room with that dormer as you do with the west... or that's how it looks on the photo.

Hi Solarchaser,

Thanks for the response and the Growatt contacts. I may have to contact them directly, if the installer doesn't help.

The SPH-6000 hybrid inverter was what was sold to me on the contract and no other inverter. It was only on the day of the install, that i was told, there would be 2 inverters and that the inverter size was considered to make full use of my panels.

Did not get your point about - it will limit generation to 3kw in the height of summer, but generally you would get better generation when you need it, ie winter.

Regarding the panel layout, there were originally 3 panels planned to be installed on the South facing roof, but on the day of install, the installer reckoned, the panels would not fit on there. These are oversized panels. I reckon, 1 panel may fit on the south facing roof in landscape orientation.

FYI, below is the original design as planned.

Thanks, CT

Solarchaser

Ahh I see, yeah if they wouldn't fit, then they wouldn't fit.

What I was saying was in theory your sph6000 could generate 6kw, whereas a sph3000 would peat at 3kw, but if you overspec panels to inverter, (5kw of panels to a 3kw inverter)then in the winter when generation is lower, the smaller inverter will respond better to the lower voltage from the panels.

cool_techie

Solarchaser said:

Ahh I see, yeah if they wouldn't fit, then they wouldn't fit.

What I was saying was in theory your sph6000 could generate 6kw, whereas a sph3000 would peat at 3kw, but if you overspec panels to inverter, (5kw of panels to a 3kw inverter)then in the winter when generation is lower, the smaller inverter will respond better to the lower voltage from the panels.

Ah. Got it now. Thanks

cool_techie

Solarchaser said:

Ahh I see, yeah if they wouldn't fit, then they wouldn't fit.

What I was saying was in theory your sph6000 could generate 6kw, whereas a sph3000 would peat at 3kw, but if you overspec panels to inverter, (5kw of panels to a 3kw inverter)then in the winter when generation is lower, the smaller inverter will respond better to the lower voltage from the panels.

Hi Solarchaser,

I just had a brainwave (shoot me down, if its more like a brain-fade though!!).

How about retaining the current Growatt MIN 6000TL-X inverter on the wall, but buying a lower spec 3kw inverter compatible of working with the SPH-6000 inverter and then switching between the two, depending on Winter (3kW) or Summer (the 6kW one)?

I am thinking of buying an inverter from fleabay, getting an electrician/MCS installer to mount it next to the existing MIN 6000TL-X and connecting plug & play sockets to both OR a diverter switch between them, so switching between the two can be relatively easy!

Would that even work or be approved by the 'authorities', since it may cause variations to the Total output of the system?

Will also need to find an efficient 3kW inverter, capable of working in tandem with the SPH-6000 hybrid inverter and capable of charging the ML33RTA batteries! My entire system is built of Growatt components and as you said earlier, they are slow to react. Hence will be looking to a better efficient model, if this is a workable solution.

Thanks, CT

Solarchaser

I think your 6000tl is fine, it's dealing with the right amount of panels on the garage imo.

I'd say the problem is the sph6000 should be a sph3000 or 3600, but I've had a look at spec sheets which say that all the sph range work on the same voltage range and same startup voltage.... which if true is really weird, but cool for you.


It makes you wonder why they would ever sell any other model except the sph6000... and maybe that's why you have that.

I doubt that you would see a benefit from attaching another inverter to be honest, or at least not one that would justify the outlay of a spark and the inverter.

In terms of the variation in output though, I dont see that causing a problem if you were to go that route.

On a brighter note, if you can hold off until April time you will generally start to see the panels produce more like what you would expect, we are just coming out of winter, and solar is always much poorer then.