Paulvdm

Hi I arrived home Yesterday at around 4pm just to find that my inverters 2 x MKSII 5-48 running in parallel had shut down at approximately 10am with buzzers beeping continuously and Red alarm LED burning. The error message number displayed was "72" (Not indicated in the user manual) and the current onboard inverter firmware is version 71.50. Can someone please shed some light on what this error message number means thanks Paul

Thanks B i will look into a firmware update

Hi Jaco and Wilfred Thanks for your input to my question. I wanted to monitor the situation again during this weekend but due to overcast weather and more load on my system I did not have any hi voltage or overcharging occurring again so i will just have to wait till i get a nice full sunny day again. Wilfred interesting point you make about the 40A charging current possibly becoming 80A as the inverters are running in parallel, I will look into that. Jaco the answer to your question on communication between Inverters and batteries is simply No there is no direct communication between battery and inverter so the battery BMS does it's own thing. With a very small load especially at night sometimes up to 3 of the 4 batteries go to sleep and turn themselves off and as you know as soon as a fair load gets drawn from the inverters the batteries switch themselves back on again. I think a possible solution to my problem will be to reduce the charging current to the batteries so that they don't charge so fast and create a more substantial load on the inverters output. My problem generally occurs when the PV's are receiving midday direct overhead sun.

Hi I have installed 2 Axpert MKSII 5-48 inverters and have set them up to run in parallel. Each inverter has a single string of 6x 330W Canadian solar PV panels (CS6U-P) connected in series with a VOC of 45.6V per PV panel so a total of 12 panels. Further to this I have a battery bank of 4x Narada 48NPFC50 Lithium ion polymer 50Ah units also connected in parallel as battery backup for night time use so a total of 200Ah. I generally do not have the utility connected to the system so the system runs off the grid. The problem I have comes from the charging of the batteries which takes place during the day via the inverters. The charging voltage is set up at 51.6V the float charging voltage is set up at 51.5V the charging current is set to 40A the low DC cut-off voltage is set to 44V. Due to the fact that my day time load on the system is very small the batteries charge at a rapid rate typically fully charged within about 2 hours of full sun on the Panels and this is where the problem begins to emanate so even though the inverters are set up to a charge voltage of 51.6V and float of 51.5V the charge voltage runs up erratically to anywhere between 60 and 69V in so causing the inverters to get hot as they are trying I think to dissipate watts from this extra high charge voltage. I cannot think that this is a healthy situation for the batteries either. Surely the inverters should not allow this set charge voltage to run away to such a high voltage just because there is a small daytime load on the inverters, if I increase the load on the system during this anomaly say boil the kettle (3000W) then the problem disappears and the battery charge voltage reverts to its set level of 51.6V. Can someone possibly shed some light on this issue. Thanks Paul