Deye 8K inverter 2 strings per mppt

[Hbbyd]

Hello guys, I have a quick question. In the case of the Deye 8KW hybrid inverter(SUN-8K-SG01LP1). It has two mppts and each can accept two strings of solar panels(attached spec sheet). Basically it accepts 26A per each mppt thus only 13A per string as stated by engineer from Deye. Is it possible to use 17A panels (Trina 660w) with condition that I only use one string per mppt. Are the mppt strings just connected in parallel or does each has its own current limiter to 13A.
Thanks for the help!

 

[BentleyJ]

If each MPPT charge controller is capable of accepting 26A, then current equal or less than that amount should be acceptable regardless of the panel configuration. Since 17A + 17A is less than 26A + 26A you are well within acceptable current limits.

 

[Hbbyd]

The thing is, as mentioned, I am scared that each string is limited to half of the 26A. Can you confirm that it works?

 

[Supervstech]

Your data sheet shows 26+26 for the 8k, so it should handle 17+17 without issue.
Bump the voltage up by stringing more panels in series and giterdone!

 

[BentleyJ]

It depends on the voltage. Overall the 8K is limited to 10400 Watts of DC input power. You can typically over panel a bit depending on your location and typical weather conditions. Lets just keep it simple. 10400 Watts / 34A = 305V. So you need to keep the number of panels connected in series in each string low enough that the wattage is not exceeded.

 

[Hbbyd]

It depends on the voltage. Overall the 8K is limited to 10400 Watts of DC input power. You can typically over panel a bit depending on your location and typical weather conditions. Lets just keep it simple. 10400 Watts / 34A = 305V. So you need to keep the number of panels connected in series in each string low enough that the wattage is not exceeded.

I won’t be exceeding this voltage any time soon Funny enough, I just posted another thread asking about the efficiency of the inverter at lower voltages.
Thread 'Deye 8KW Inverter efficiency'
https://diysolarforum.com/threads/deye-8kw-inverter-efficiency.44651/

 

[kolek]

It depends on the voltage. Overall the 8K is limited to 10400 Watts of DC input power. You can typically over panel a bit depending on your location and typical weather conditions. Lets just keep it simple. 10400 Watts / 34A = 305V. So you need to keep the number of panels connected in series in each string low enough that the wattage is not exceeded.

I own this same inverter, the maximum PV input voltage is 500V, please don't get confused and think it's 305V. In theory, you should be able to overpanel meaning provided you don't exceed the VoC or the rated amperage up to the ISC which is:

Max. PV ISC (A)​

44A + 44A​

That means a total of 22A per string x 4 strings total (2 per MPPT). Above that level you will experience amperage clipping.
I'm actually in the process of trying to verify how much overpanelling is possible with the Deye 8K.

EDIT:
I'm finding that different inverters from Deye may have different specs even though they have the same model number, so verify your labels, not the specs it says online for this inverter.

 

[natehawkv8]

I own this same inverter, the maximum PV input voltage is 500V, please don't get confused and think it's 305V. In theory, you should be able to overpanel meaning provided you don't exceed the VoC or the rated amperage up to the ISC which is:

Max. PV ISC (A)​

44A + 44A​

That means a total of 22A per string x 4 strings total (2 per MPPT). Above that level you will experience amperage clipping.
I'm actually in the process of trying to verify how much overpanelling is possible with the Deye 8K.

EDIT:
I'm finding that different inverters from Deye may have different specs even though they have the same model number, so verify your labels, not the specs it says online for this inverter.

@kolek Any idea the max wattage you could get using only one of the MPPTs (one pair of PV wires to Deye) in the 8K?

 

[kolek]

@kolek Any idea the max wattage you could get using only one of the MPPTs (one pair of PV wires to Deye) in the 8K?

Mine says on the label stuck to the side of the machine "do not exceed 3250 watts per string." So I'm not planning to exceed that.

 

[Montypaks]

I have a question regarding this. Mine is a Deye 5kw inverter. It's got 6500W max solar DC input, with 2 mppts... 500v 13a max rating per mppt.
I'm not sure if that equates to 3250w per mppt. Didn't find this info in the manual.

I plan on oversizing my panels to further reduce grid reliance on cloudy days.

I currently have 16x 300w panels.
Can I parallel two strings (2 strings of 8x 300w panels-7a each) making it 300v 14a into mppt1 (500v 13a max rated)

And on mppt, I'll have a single string of 10x 460w panels (new) making it 420v 11a into mppt2.


I've seen several folks mention that the only downside to oversizing panels is the cost. The inverter will only ever just pull what it needs (rather than the panels pushing into the inverter)

Is this advisable? Am I about to make a huge mistake?

Cheers

 

[RCinFLA]

Although each MPPT input can accept up to 13A + 13A amps there is a limit on what the total SCC can handle (10.4 kW). The two MPPT controllers are combined on the SCC HV DC output so the output stage has this power limit based on SCC heat generated.

The Deye and SolArk's have an intermediate power converter between SCC output and inverter's two 250 vdc HV DC buses to provide two isolated 250 vdc outputs to share the PV power between the two series connected 120vac inverters. This intermediate converter has a maximum power limit.

The variables that limit the maximum PV input current are what the Vmp voltage of the array is and how much power is on each of the two separate MPPT inputs combined.

If you have a PV array that has a maximum Imp current above 13A, the SCC will limit the current to 13A. The SCC may limit the current below the 13 amps maximum depending on how high the Vmp is, and if the other MPPT controller is also accepting power such that the sum combined power exceeds 10.4 kW.

There is a spec for maximum Isc of 17A which may mean there is limit on a startup surge that is safe for the SCC so you want to not exceed a 17A array maximum Isc current.

The SCC input may get exposed to maximum Isc of array while it is doing MPPT search. Typical MPPT search startup procedure is to measure Voc then start an upward MPPT peaking search from about 0.6 x measured Voc voltage. When it goes to 0.6 x Voc initially, it can get close to Isc input current of the PV array connected to that port. In order to perform the MPPT search, the SCC cannot limit input current during the actual MPPT search time.

Typical Vmp of a silicon PV panel is about 0.80 to 0.85 x Voc. Typical Imp is about 0.92 to 0.96 x Isc.