RolandS

Hello, currently I am also doing experiments with additional MPPT charge controller parallel to an Axpert Max Duplex 11K. Batterie is an LFP Pylontech Battery Stack (6xUS3000C). My PV generator basically exists of 5x3kWp string. MPPT1 of The Axpert max is connected with 3 strings in paralell (9kWp and MPPT2 is connected to 2 strings (6kWp). As each MPPT can only manage 5.5 kWp, the System will waste probably some earnings in summer, but in winter overloading will give an improvement. I have an additional PV Generator with different PV Modules (MPP Point around 25 V, 16 A each, 6 Modules, but five of them are oriented SW, one is oriented NW, and so does not get much sunlight, or at least less than the other five modules. All modules are vertical 90 degrees. O.c. Voltage of 5 Modules in a string is around 166 to 170 V in summer, plus 20 % if its really cold could be up to 204 V. MPP Voltage of 5 modules will only be around 125 Volts. That is too low for the Axpert Max, here MPP Range Minimum is 150 V. Integrating 4 of the modules in two of the existing strings is OK frommax. Voltage and is working, but maybe not agood idea, as module orientation is completely different: SW 90 degrees slope vs. SE 22 degres slope. No idea how good Axpert Max can handle that. I think at least not if only the 2 Modules get sun light. So currently I connected experimentally an additional EASun MPPT to the batterie stack, and connected 4 SW90 modules to it. It worked and will work at least if the additional MPPT is configured the right way and battery is not too full. (That will help a lot winter, even it will probably not work till battery is completely full.) There is a difference in Coulombs Setup and mine: He has Pb Batteries and no BKS Connected to his Axpert Max. So the inverter and mppt is able to control charging by only measuring voltage and current. In my case this is not possible, as my Pylontech Stack has and BMS and the Inverter communicates with the BMS. Here it gets max. allowed charge current and SOC. I wonder if the inverter can handle the situation that actual current to the battery is higher than the current coming out of the inverter. It will depend on the regulator algorithm. A normal PI(D) regulator would work, but if there is implemented a plausibility check between outgoing and bms measure current, maybe there will be situations this will fail. I will continue to do the final connections for only 4 Modules and the additional EASun MPPT. Than observe the earnings this winter, and beeing a little bit unhappy not to use at least the 5th 450 Wp PV Module Other possibilities would be: 1.) Connect all five 3 kWp strings to one MPPT of the Axper Max. (3 times overload, just limited by the firmware!) Connect 5 or even 6 of the SW/NW Modules to second string, but still be under 150 V Voltage n MMPT. 2.) Buy an new extra MPPT that can handle higher Voltages. But Victron is quite expensive and other higher Voltage MPPTs are very rare. There is one at Alibaba with 230 V max. DC Voltage. Does anyone has experience with that device ? Is there any experience in the forum with Axpert max, Li Ion Battery with BMS communication to the Axpert Max and an additional connected MPPT charge controller Gruß Roland

Hi ! I am operating an Voltronic Axpert MAX E 11 K Duplex Inverter, connected to 3 pieces of Pylontec US 3000 Batteries (10 kwh netto capacity). I charge the batteries on cloudy or snowy days with an Briggs & Stratton Promax 9000 generator (synchronos avr generator. 7 kva continous load). Charging is only possible if attach an electric heater in parallel, and start charging at lowest current (2 A, 50 V) and increase it step by step. I managed to raise charging power up to 4kW (80 A),but this was not stable for a longer time. 3kW was stable to charge several kwhs into the battery. It is a pity, as the Charger would be capable of charging with up to 150 A. For sure that is 7.5 kW, that's more than the generator can handle for longer time. But it seems to be, that you need twice the generator power, you intend to use for charging. I have to try if it helps to raise voltage and frequency of the generator a little bit. Maybe to set it to 52 Hz and 240V. Gruß Roland

Hi ! You can easily order aluminum profile 40x40x3 mm rectangular angel and cut it into aprox. 46 cm pieces and drill in two holes for fastening them by 2 screws each in the 19 " rack. That was the cheapest solution for me. Gruß Roland