Hi Guys,

I upgraded to a Sunsynk 8kw inverter about two months ago. I did it in stages to see how the performance would change having gone from a Mustek 5kw.

All North Facing. - Jhb - Full Sun

I kept the old panels. Initially placing them on separate strings.

12x330w Panels - Initially it was 6\6 on each string. (3900w Total)

Overall I gained Roughly 20% + efficiency.

My next step was to expand my array.

I moved the old panels onto a single string and they are currently in a 8series and 4 parallel config.

My thought process for both sets of panels was Voltage. I was recommended to get as close to 375v and not go over 390v.

So old panels spec is

Mustek Solar Panels (Mono)- CNBM 6P-330

47 V

9.38A

So 47*8 = 376

I placed the rest in parallel.

I was not worried about clipping on Amps as my thought was get to your optimal power early as possible and like wise in bad weather \ cloudy it will help.

The 2nd String I purchased JA Solar Deep Blue 4 Bi-Facials

JAM66D45-600/LB

VOC 47.7 V

Vmp 39.44

Isc 15.95 A

Imp 15.21

8 in Total , Additional 4800W

47.7 * 8 = 381.6V

These I put in a 7/1 layout series parallel. I both strings I was aiming for Voltage for better low light response etc thus the different splits.

Yes the system is working better. It's been just about two months now however I am not convinced I have chosen the correct layout.

Unfortunately, weather has been poor but we did have one or two weeks of good weather as well.

I have not had the chance to properly load the system yet by turning lots of things on in the middle of a clear day.

Max I have seen was only been 6000w and rarely Normally 5000ish.

I do understand if the load is not high enough it won't ask the panels to do more. But even so.

I have restricted my 4x 5kw Lithium's to only charge at 60amps in total. E.g. Longer slower Charge.

It is only making pear power roughly 12:00/13:00ish. Takes a long time to get there and then drops away again.

I hardly ever see my amps get very high which I was expecting.

Yesterday in Sunshine in Jhb I got the below

Volts seems to hover around 150V to 200V - Was also expecting more ?

Amps climbed to 16.5 then dropped off again.

In my head. I was going to instead of having a "hill" shape PV charge it would become more like a table mountain.

Get there earlier, stay there longer if required.

It is better. But possibly on 20% better.

I do see that each strings amps generally seem to be fairly close generally.

I can see in early morning or late night the string with the Bi-Facials does do quite a bit better.

Have I set them up incorrectly in the series parallel part ?

Is the Sunsynk not happy with different types of panels on each string ?

Or am I just expecting too much ? I don't feel I was.

One Last note. This was not the installers wrong choice if that's what it is.

It's what I asked for.

Any help would be appreciated.

@Dry_Reef This is the confusing part for me please clarify. "I moved the old panels onto a single string and they are currently in a 8series and 4 parallel config." You have 12 x 330w panels on original array and now you have 8 in series(8s1p) how did you wire the remaining 4? Hopefully not in parallel to the 8s?

Hi @Dry_Reef You are putting panel strings of unequal length in parallel to each other. Don't do that, keep the parallel strings of the same length. Also, your terminology is a bit non-standard, so what you're doing is a bit unclear. In any case, rather do the following: ...

For MPPT1: - Use the old 12x330w panels in a configuration of 6s2p, that means create two strings, each of 6 panels in length, put those two strings in parallel to each other, and then feed that combined set of strings to the 1st PV input. Point all these panels in one direction on the roof, eg. all North or all East, etc.

For MPPT2: - Use the 8 new panels in a single series string, and connect all 8 panels in series into your 2nd PV input. Do NOT put any of these panels in parallel to each other. Point all these panels in one direction.

For PV1 you can expect an open circuit Voltage of 6x47.0Voc, which equals 286,2Voc, but while it is operating, you're more likely to see 6 x 37.5Vmp, which equals 225Vmp and then up to 2 x 8.89A current at full power, or up to around 17.5A current.

For PV2 (edit: previously read PV1; Typo.) you can expect an open circuit Voltage of 8x47.7V, which equals 381.6V , but while it is operating you'd see 8x39.44 Vmp, which equals 315.5V, and then up to 15.21A current.

This is your best configuration. I understand you're trying to chase an optimum Voltage, but the setup here will also work fine, all within normal range, and without clipping of any current, and without any over-Voltage.

It's okay to increase the charge rate of the battery bank. Check the battery spec sheet for the ideal recommendation, but instead of 60A you can typically set the inverter to charge 120A at least, and still be treating your batteries well, considering you've got 4x5kWh batteries.

I hope this makes sense. If there's any doubt, please double-check it with someone like @TaliaB

Edited April 11, 20251 yr by GreenFields

6 minutes ago, GreenFields said:

Hi @Dry_Reef You are putting panels of unequal length in parallel to each other. Don't do that, keep the parallel strings of the same length. Also, your terminology is a bit non-standard, so what you're doing is a bit unclear. In any case, rather do the following: ...

For MPPT1: - Use the old 12x330w panels in a configuration of 6s2p, that means create two strings, each of 6 panels in length, put those two strings in parallel to each other, and then feed that combined set of strings to the 1st PV input. Point all these panels in one direction on the roof, eg. all North or all East, etc.

For MPPT2: - Use the 8 new panels in a single series string, and connect all 8 panels in series into your 2nd PV input. Do NOT put any of these panels in parallel to each other. Point all these panels in one direction.

For PV1 you can expect an open circuit Voltage of 6x47.0Voc, which equals 286,2Voc, but while it is operating, you're more likely to see 6 x 37.5Vmp, which equals 225Vmp and then up to 2 x 8.89A current at full power, or up to around 17.5A current.

For PV1 you can expect an open circuit Voltage of 8x47.7V, which equals 381.6V , but while it is operating you'd see 8x39.44 Vmp, which equals 315.5V, and then up to 15.21A current.

This is your best configuration. I understand you're trying to chase an optimum Voltage, but the setup here will also work fine, all within normal range, and without clipping of any current, and without any over-Voltage.

It's okay to increase the charge rate of the battery bank. Check the battery spec sheet for the ideal recommendation, but instead of 60A you can typically set the inverter to charge 120A at least, and still be treating your batteries well, considering you've got 4x5kWh batteries.

I hope this makes sense. If there's any doubt, please double-check it with someone like @TaliaB

Thank you. That makes sense.

Sorry about the terminology. :)

I'll try that. Have a feeling it means my new panels will boost in productivity all being in series.

I was worried about over powering on the volts.

I'll try get it changed up in the next week or two.

Is there any truth that the inverter will try split the load to the smallest string ?

52 minutes ago, Dry_Reef said:

Is there any truth that the inverter will try split the load to the smallest string ?

In your case you will use Mptt 1 and Mppt 2 so no the inverter will use all pv input power from both Scc's and convert it to ac output. The 60 A charge limit is one of the factors that is limiting your pv generation. I agree with @GreenFields at least 120A as you have 20kwh(416ah) battery capacity charging at 0.3C = 416 x 0.3=125A that is totally a safe zone for your lifep04 battery pack. Each battery will receive ~31A charging current.

@Dry_Reef ,

Not sure if I understand your "These I put in a 7/1 layout series parallel." statement correctly.

Sounds like 7 x 600's in series in parallel with 1 x 600's.

That is not a good match at all, as parallel strings must always match in Voltage.

Would be nice to use the 330's in a string parallel with some 660's, but chances of matching the voltage of the 2 strings to within a few Volts are going to be tough.

Here's what I think.

If your roof layout allows it, an option is to try 4 string of 3 x 300's + 2 x 600's. Then all string voltages with match 100%. You will loose the extra Amps on the 600's, so also not ideal.

Only problem you might have is a visual problem. I'm sure the 600's are a bit (+-10cm) longer and wider that your original 330's.

Best bet would be to run 2 strings of 6 x 300's (6S2P) on one MPPT, and the put 8 x 600's (8SP1) on the second MPPT. Going 8SP1 will result in Voc = 47.7 x 8 = 381 V, without Temp Co-eff changes. You are still 69V below MPPT Vmax, so plenty of headroom for very cold winter mornings. I run a 2 x 8P2S x 365's on my 8.8, and Amps rarely go over 17A (& 350V) - per MPPT. (18.5A with cloud edge effect). Well below the 22A current limit. Spec on these 365's are Isc = 9A.

Note to self: As my 8.8 is one of the early models with 18A max. MPPT's, I have upgraded the FW a year ago or so for the 22A capability, but have no means of getting to test if the HW can indeed run to 22A.

I've seen 451V on 10 x 550's, but that's on a Deye 12kW 3PH, which has got higher voltage MPPT's than the 8.8