MPPT voltage
Hi there
Hopefully someone can help me, I have had a couple of problems with our install ( 10 X 545w JA panels, 5kw Sunsynk hybrid inverter and 5.12kwh Sunsynk battery) since conception in April.
I have queried that the panels are in one MPPT, as the panel voltage added together comes to over 425v. The installer has said he has been in contact with Sunsynk, they have advised that is ok to use one MPPT as the PV voltage input is up to 500v.
Can anyone advise if this is correct please? I have contacted Sunsynk myself but they keep asking to speak with the installer.
Many thanks
108 Views
Hi Sobeekeeper
There are lots of SunSynk inverters and they all have different specs. On the side of your inverter will be a big silver sticker. There will be a line for PV Input Voltage and another for MPPT Input Range. Mine (on a 3.6kWh inverter) is
PV Input Voltage 350Vdc (125Vdc - 500 Vdc)
MPPT Input Range 150Vdc - 425 Vdc
My panels have an open circuit voltage of 46.55v at 20 degC Mine are also 545w JA Panels but I do not know exactly the model of yours so you should check for yourself and not take my word for it
This means I could not connect more that 11 panels at 20degC without risk of damaging the inverter as that would be more than 500v. In fact the number may be lower as the open circuit voltage rises as temperature drops. I would use a safety margin of 15% so I think the safe number I would be happy with would be actually 9 panels. If others used a smaller safety margin then the number would be higher. I have seen 0.3 volts per degree which would be 6 volts or 13% at 0 degC but that is still not 10.
However the MPPT only searches for voltages between 150v and 425v so on the sunniest days you would waste energy if you had more than 425v which also happens to be 9 panels at 20 degC. I assume the sunniest days are also the warmest and panels can get warmer than 20 degC on a sunny day so perhaps no energy would be wasted at all with 10 panels or perhaps it would be so little as to not matter.. If there was a very sunny cold day perhaps?
The sweet spot for my MPPT though is 350Vdc which is between 7 and 8 panels
If the specs of the MPPT on your inverter are not the same as mine your results would be different. However, if they were the same, in an ideal world I would have split your panels into two arrays of 5 with a Voc of 232 Vdc at 20 degC unless there were other factors, like wishing to use the other MPPT for something else, in which case I may have only bought 8 or 9 panels (but of course that would have reduced my output on some days by 10 or 20% so other would disagree especially as this is right on the margins and there could be safety margins built into the inverter that I have not taken into account).
Hope that helps.