JohnSand

I'm back again with some feedback from alterations I've made. 1. Added a couple of heavy diodes in parallel (each with a few turns of series copper to equalise the current). 2. These are connected as a series blocking diode to the +ve output of the shadier PV string. 3. Result has been that so far that the inverter MPPT is starting up automatically in the morning. Almost always. I do see the odd glitch when from time to time the machine reverts to alarm ALA 33 and refuses to draw PV current. It is hard to see any triggering event correlating with this. 4. I'm sure I'm on the right track. Presently the setup is a SAGM (String And Chewing Gum) lashup but proves something positive is happening. 5. Next step will be to duplicate the diodes to the second PV string and see if this cures the issue completely. 6. Upon that glorious event I can go ahead and fix it up permanently NSAGM (Non String And Chewing Gum). -John

Thanks Coulomb, These are great suggestions. I have my own electronics workshop so there are no real physical challenges here but I hate taking action without knowing WHY it might fix things. I'll work thru these & post results later.

Coulomb, I think the current of ~50A has to be PV panel current. It is shown on the LCD along with Vpv of ~150V under the designation P3. It looks like this. Vpv 150V P3 I 49A or something like that so it refers to the PV output (I'm confident). Again, the usermanual is so poor it doesn't even describe the display features, had to figure them out like the rest by trial and error. I'm in the RSA, Free State and these are winter conditions at altitude ~1400m with very clear skies, also the panel pitch is 45deg and azimuth NNW. An excellent setting for the PV. These panels are Korean Bi-facial 72cell, 675W peak, Voc 55.67V, wired 3S2P. An instinct of mine -backed up by a couple of other cogniscenti- is to rewire to 2S3P, this will lower Vpv to max 110V. I'd happily do that straight away but it's a dog of a job & will require me to strip the panels off (45deg pitch!) then rewire and refit, so I'm looking for other easier experiments first. As for minimum MPPT voltage being possibly misrepresented, I do note that the MPPT works well in diminishing sunlight right down to 60+V drawing a few amps, 2-6A. Another observation is that startup is inhibited in full sunlight until BOTH strings are fully lit, if even a couple of cells at horizontal top edge of one panel are shaded the MPPT will not start up. Both strings have to be completely clear then startup is guaranteed. That confuses me because if one PV string is generating 150V but is unobstructed then how can the other string in parallel drag it down? There are bypass diodes in all panels (I suppose).

Just seen in the manual as well.. MPPT/PWM input voltage range 48V: MPPT60-200VDC (or PWM60-105VDC)

To add to the story, it is somewhat odd that I do have the MPPT drawing current while there is diffuse light, voltage maybe 140V, current 2, 4, 6 Amp. The shading later also only affects one of the two parallel strings of PV panels, the other is in full sunlight well before 10AM but the system is still un-re-settable till there is full on sun.

Thanks Greenfields! Actually my inverter is not the model you assumed but very close. It's given as VX-10048M-FS 48V 10000VA MPPT. 'Hybrid Solar Inverter' see pic below. The max Voc is definitely shown as 48v-MPPT200VDC in the user manual. So I'm well within their range, I daren't restring to above 200V.

Hi All, I too am having issues with a "Fivestar" inverter I've bought -did it online & the price was right so I knew I was taking a chance. Firstly & worstly is that the 'service' is non-existent. After repeated calls to the vendor all I am told is that their workshop will attend to the unit if I bring it to them for inspection. They're in Johannesburg, I'm in the FS. The fault is a very minor one which should easily be treatable over the phone, but, let's get on with it.... 1. Unit is 10kVA, 1ph. It is not expected to regenerate as grid-tie. 2. PV panels are 6off arranged 3S2P. Inverter spec allows Voc <= 200v. The panels provide Voc of <! 155V (measured and expected). 3. Almost always at first light in the morning the unit sees the PV voltage and is obviously trying to home in on a MPPT current draw. it does this while the panels are diffusely lit. 4. Once the sun gets going there is a region of shadow on the panels due to building structures, which diminishes to zero by 10AM (early July). During this shaded period the unit goes to an alarm state and refuses to draw any PV current, although the Voc is shown as 140-150V or so. Repeated efforts to reset the machine keep returning me to the Alarm, it is shown as ALA 33. ALA 33 is not given in the 'user manual' ...of course. 5. Once all shading is gone the PV MPPT can be reset by open circuiting the panels for +/- 20seconds then closing the isolator again. It's a guarantee the whole machine springs to life, draws 40 or 50Amp at 140V+. It will continue flawlessly till sundown. 6. Next morning I have to repeat the process to get anything from the PV. Is there anyone out there in PowerForumLand who can advise me? bestos, John

I want to ask a very similar question. I have a Fivestar 10kVA model VX-10048M-FS 48V 10000VA MPPT. So far I have most of it working but with the exception of the PV panels input, the display confirms 145Vdc is reaching it but it draws no current from the PVs and flashes an alarm ALA 33 which is not in my 'User Manual' ! I doubt it is difficult to sort this out but the frustration is the skimpy and incomplete documentation I have. Is there anyone out there with better info? I'm in the FS, Deneysville. -John