Jakeser Posted February 12, 2019 Share Posted February 12, 2019 Hi All I've received very valuable input from members here before so this is obviously my first stop for advise now that I'm looking to expand. I have a 3.6kw Infini hybrid grid-tied inverter with a string of eleven 245 w panels (bought the system secondhand). I have a single Pylontech US2000B Plus connected. The string is north facing but gets shade in the afternoon so I thought it would be clever to add another string to the second floor roof facing west, and connecting the two in-series string in parallel (and adding another pylontech to last longer outages). It seems this will not work as the lowest voltage (the shaded string then) dictates maximum output voltage. So I read a multi string inverter may be a solution, but seems costly. Is there any workable option that won't cost an arm and a leg? Thanks Jaco Quote Link to comment Share on other sites More sharing options...
DeepBass9 Posted February 12, 2019 Share Posted February 12, 2019 Just get a stand alone Mppt for the other string. They are quite cheap and turn up second hand from time to time. Quote Link to comment Share on other sites More sharing options...
SOLARWIND Posted February 12, 2019 Share Posted February 12, 2019 I was using an IMEON 3.6 with 2 strings on one MPPT. The one string consisted of 9 x 310 Wp in series This array was North-facing. The other string had 9 x 170 Wp modules, also connected in series and this was West-facing. The trick here was simple diode-isolation between the two strings and it worked like a charm, seeing that the two arrays never peaked at the same time, so the slight difference in voltage did not matter. The negatives where tied together and connected together and to the negative terminal on the PV input of the inverter. The two positives I connected to two diodes (positives to anode of each diode and the two diodes where on a heat-sink with their cathodes (K) common to the heat-sink itself). This common point was taken to the positive input on the inverter. That's it! I don't think a heat-sink was necessary and smaller diodes with sufficient voltage and current ratings will probably do, but hey! I had this piece of hardware lying around, so I used it! A good source of such two diodes is found inside some switched-mode power supplies, where two diodes are already combined in one package with three leads. (A-K-A) (They are used as rectifiers where the transformer has a centre-tap). Most of them are Schottky diodes with a very low forward volt-drop. Quote Link to comment Share on other sites More sharing options...
Jakeser Posted August 11, 2019 Author Share Posted August 11, 2019 Thanks guys... thought no one replied as I didn’t get email and had not logged in due to this... both options seem workable although the diode seems a cheaper option? Quote Link to comment Share on other sites More sharing options...
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