Star Harvester

Hi Silver. Do you know if all the current Mobile Power Series (drop ins for lead acid replacement) come with onboard BMS compatible with a Voltex MKS Plus 24V 3kVA Inverter? The manual for the Axpert looks identical to this inverter so I think all from the same production line in China, different branding here.

Thanks for advice! Good to hear voltage between the W and E strings will be within 10-15%. Just one thing which has me confused. If I connect the external MPPT directly to the battery/DC bus, which is also connected to the inverter's battery connection, will this not mess with the inverter? The inverter also has to charge the battery from the grid and do battery equalization since it is lead acid batteries so I am not sure how it will behave if there is an MPPT connected to this same DC bus and they are different brands and not in communication with each other like a full Victron setup for instance. In the inverter settings I am thinking of setting the output source priority and charging source priority as shown in attached pictures. Solar as first priority charging source can also work possibly. I basically want to use solar power directly on loads and always keep the battery fully charged to provide back-up during rolling black-outs/loadshedding which happens frequently here. The batteries are not new, not LiFePO4 and borderline too small to carry connected loads through a rolling black-out slot so I do not want to cycle them too much. Better batteries are on my wish when the budget allows.

Thanks for the insights everyone. Please see attached my roof layout showing the chimney on the North facing roof. Just to make sure I understand correctly, you are recommending doing the following, 1 String - 2 Panels in series East facing 1 String - 2 Panels in series West facing These two strings in parrallel via a combiner box into the Inverter's built-in MPPT For the power output, current for the 2 strings in parrallel will sum i.e. Istring 1 + Istring 2 = ITotal but since the two strings are combined and then fed into only 1 MPPT will voltage in the power calculation be equal to the string with the lowest voltage in the array (due to shading)? The solar panel datasheet shows a reverse current Ir of 20 A, does this mean current up to 20A can flow from the string with higher voltage to the string with lower voltage? Do combiner boxes typically include diodes to prevent current from the high voltage string to low voltage string. Then the last 2 panels on their own in series fed into a separate MPPT connected straight to the batteries on the DC Bus which is also connected to the inverter's battery connection. Perhaps I can squeeze these 2 onto a North facing pitch

Hi JTK, thanks for the reply. I assume you recommend 2 E and 1 W for each string to ensure the Voltage is always below the inverter's max with a safety margin for colder temperatures? I have pretty much no experience with solar panels only inverters and batteries so please excuse the layman. But what exactly happens when for instance one panel facing West in a 3 panel string gets no sun (high pitch roof) and the other 2 facing East gets full morning sun, If they are in a series string am I right in saying the current for the whole string will be zero? While the 2E panels will have voltage and the 1W will have zero voltage? So pretty much the whole string generates zero power?

Hi All I have the following setup currently which functions merely as a lightweight utility back-up for essentials, Voltex MKS Plus 3KVA Inverter with single built-in MPPT charge controller 2 x 100ah Royale DC31 batteries in series for 24Vdc Lady luck recently blessed me with 6 x second hand IBC Monosol 370 OS9-HC panels for an absolute bargain (almost free) from a friend. The panels are only 1 year old and all tested and fully functional. Now I realize my existing system does not do these panels justice, especially the batteries which aren't even LiFePO4 but I am not in a position currently to spend big money and would really like to take on the challenge of integrating these panels into the existing system at absolute minimal cost. Every little bit helps and any saving on the Eskom bill is welcomed so I am not expecting the stars but hoping to fall on the moon. The Open circuit voltage of the panels is 40.9Vdc and Short Circuit Current of 11.52A so a series string will not work since the Inverters MPPT has an operating range of 30-115Vdc and rated current of 60A. Max solar voltage is 145Vdc but I think MPPT cut-off will occur at 115Vdc as per above. Inverter and Solar Panel specs shown on photos and datasheet below. My roof is also tricky with the only big North facing option having a chimney smack centre creating shading problems on some of the panels as the day progresses. Alternatively I'll have to do an East-West configuration with 2 parallel strings (not ideal with 23 deg pitch roof) What it boils down to is I will have to do some kind of 2 string (2 panel each - 2 panels to spare) parallel configuration. The question now becomes can this be done without purchasing 2 additional charge controllers (one for each string) and if I feed both strings in parallel into the inverter's built-in MPPT, via a combiner box, will the shading or East-West setup drag the performance all the way down making the exercise a waste of time or will there be enough performance making the effort worth it? If no way without separate charge controllers, how would I wire this into the existing setup and any recommendations on MPPT's to buy? Other costs I can think of is the Combiner Box, cables, 2M/2F photovoltaic connectors and tiled roof mounting brackets/rails. Any advice on best place to buy? Any thoughts are much appreciated! 2005700074_IBC MonoSol 370 OS9-HC_Data sheet global_EN.pdf

Wrong section sorry, moved to general discussion

I have experienced the same phenomenon with inverter fans running non-stop and charging process never stopping. I have an MKS 3K 24V Plus with 2 x 100ah Royale DC31 batteries running without solar merely as utility backup. The batteries as confirmed with supplier are flooded type. On my display it keeps showing the last bar (in battery charge level) flashing and the charging never completes. Even after 10 hours +. My bulk, float and abs voltage are set correctly on defaults yet the inverter takes the battery voltage up to 29.2 which exceeds all of these parameters, verified with a multimeter. My guess is that this has something to do with battery equalization seeing as the battery type 05 setting is on FLD. I changed this to AGM and the inverter stopped continuously charging and blowing the fan. Everything seems to be ok now but I don't know if this is ideal since one would think that flooded batteries should be charged on the FLD 05 setting not AGM. I don't know if battery equalization should really take this long and whether the voltage should go this high. And even if it does and after one cycle it will only do this again after 30 days as per setting 37, I am not willing to take the risk of a bug causing this frequently when I am not around. Frequently charging the batteries to 29.2V+ for prolonged periods makes me a bit nervous. So for now I am just leaving it on AGM battery type setting even if it is not ideal for long term health of flooded batteries. Any comments are most welcome.