I have BlueSolar MPPT 150 / 75 solar charger hooked up to 3 in series 375 W solar panels and 48V LFP battery. Solar panels have 41,92Voc and 34,38 Vmp. Sun is low this time of year but the panels are vertical and I would have expect the voltage to read about 100V, but the MPPT controller showed max 54.3V which means that the MPPT is not able to charge batteries as it would require +5V PV voltage.
Has anyone had similar issue and if so, what was the cause? Or any ideas how to debug the system? Also is the hard limit of 150V in relation to Voc or Vmp? If it is for Vmp then adding one more panel in series might help if the problem is just that too little sun. Voc would go over the voltage limit (especially when weather gets cold…)
MPPT voltage limit should always be based on Voc corrected to the lowest temperature at your location.
Do an open circuit voltage test and short circuit current test on the string as a whole and each panel in case you have a failed panel which is dragging the voltage down. Also check for poor contacts in any fuses, isolators, terminals and connectors.
Thanks. I thought so and on re-read datasheet clearly said so. Problem seems to persist. I have (had) multiplus-II in the system as well. I thought It might have contributed to the problem with incompatible settings. So I went and disconnected the battery fuse when taking the system apart. At which point there was a distinct “bang” noise from the Multiplus as it went dead. Puzzled by this, I started debugging things and noticed that BlueSolar puts 115V to the battery terminals when the battery was disconnected. I suspect this might have something to do with the “bang”… I pray that I have not busted my Multiplus completely…
So follow up question: I am leaning to believe that the BlueSolar that I have is not working properly. Should the bluesolar expose panel voltage to battery terminals?!
I would hope not…
Also if someone has idea how to resurrect the Multiplus, that would be nice to know…
Panel voltage should not get through to battery terminal unless there has been a major internal failure.
I know it is after the event, but if disconnecting output from an MPPT you should always isolate the panels first, I am sure the manual makes this point.
Yes this was an expensive lesson… MPPT charger is definitely busted, same behaviour on 12V battery, so it definitely is not due to panel issue. I did not find mention of disconnecting solar panels before disconnecting battery from the manual, but it is probably mentioned there somewhere…
Have to see how to guard the system from this effect in the future. This would be same as if BMS would cut off battery due to over voltage or other reason. It would also leave the circuit open on battery side…
The 150voc (at min temps) is a hard limit. PV spds can help not saying they will totally save everything.
The mppts can handle batteries disconnecting under load if there is somewhere for production overshoot to go - so in your case a multiplus load or other load.