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I have 20 X 275 watt Trina panels wired in 4 strings of 5 panels. 2 parallel circuits running to 5kVA EasySolar with 250/100MPPT. When first connected PV volts approx 170V. Now getting PV volts exceeding 250V when battery at 100%.
Open circuit voltage of panels is 38.7V, so 5 panels in series should be 193.5V. How am I getting up to 257V?
@JohnC John, we have checked the volts from the panels, and both were 141V, but PV voltage on EasySolar reading 203, and fluctuating. With one PV isolating switch on and the other off, I'm getting 141V on the line side and 90V on the load side of the isolated string ( backfeed from MPPT). There shouldn't be voltage backfeeding from the MPPT back out to the panels?
The voltage now fluctuates from 200 to 245V constantly, which prevents proper charging of the batteries.
This is the 2nd MPPT that we have had problems with. This one has lasted 12 months. Different fault than previous.
System is on Aore Island, Espiritu Santo, Vanuatu, so getting replacements isn't easy.
I'm going to reduce the strings from 5 panels to 4 panels to see if we can keep the voltage below 250V, and at least keep the batteries charged, until I can get a replacement, and get there to install.
That isolated '90V' is strange. If it's measured with a multimeter, even stranger (impossible?). Sometimes a small residual V might show on the mppt pv input, but maybe only ~1V on a 48V system. I see that sometimes overnight.
If it's a reported V, maybe a 'zero-error', adding to the actual ~140V and causing your issue. A full power-down should confirm that.
There's a couple of Victron dealers listed in Port Vila (see Victron website). Maybe there's an 'outpost' of one of them up your way? you could ask.
Sorry, I've run out of ideas..
Hi. First place I'd look is to your panel wiring. Unless you installed it yourself, my guess is that the installer has seen the 3x wire pairs into the mppt, then decided that 3x strings would suit (him) better. So you may have 6x or even more panels in each string..
There's virtually no way that 257Voc could be reached normally, wired as you say.
It *will* damage the mppt, so best to isolate the pv until you can confirm all is set up correctly.
@JohnC Thanks John, The 4 strings are paralleled at the 2 isolating switches, with a single pair from each running back to the MPPT. The PV voltage has been between 155 & 170V up until approx a month ago. It has then started to increase slowly to alarm state 4 days ago. It's now alarming as soon as it gets daylight. I'm not on site, so a friend is going to check the voltage at the PV isolating switches to confirm the exact voltage coming from the panels. There is only one string energised at present. If they are 155 to 170V, then I believe the MPPT has a component failure causing this problem.
Mark - Electrician but solar novice
Yeh ok. If you're certain of the panel wiring, then you should see those lower V's. The mppt can't boost them, and if it's misreporting high V then it's likely faulty.
There's no adjustment to cure that, but you could try a change of firmware and/or a full power-down (from both sides - leave it for awhile) to see if that might 'unknot' it.
Failing that, a return to dealer..
