man0war69 Posted September 30 Share Posted September 30 Hi there. I currently have my geyser running off Eskom and the rest of my house running off two growatt 5kva parrallel connected invertrs with 2 strings of 5x550w pannels. Each string goes to one of the two growatts. I just installed 2x7.68kwh lithium batteries and now have my old OPzS battery bank free. I have a spare 5kva Axpert Hybrid inverter, and of course now have a 48v 10kwh lead acid battery bank free to use. I wnt to connect my geyser (1.5kwh element) directly to my Axpert inverter powered by the lead acid batteries. Then use the Growatt parallel inverters as my "utility" input and set my charge times from utility on the axpert to only charge during certain hours of the day so that i can indirectly use the pannels connected to my growatts to charge my lead acid batteries during the day when there is suficient sunlight. Thtis way i do not need to buy any pannels to directly connect to my axpert for geyser and use the existing panels kind of in a dual sence. Attached is a diagram of what i want to do. Please give me your opinions on whether this will work or not. Quote Link to comment Share on other sites More sharing options...
Sidewinder Posted October 7 Share Posted October 7 @man0war69, My initial reaction is that you may have too few PV to sustain both system's batteries cycles on a daily basis, never mind a few consecutive cloudy days. It may just work out well enough, but if family is involved, I would just include a changeover switch between Eskom & Axpert, and an Axpert bypass switch as well. That way, if anything fails on your premises, you can bypass the failures. Just doesn't work well when LS happens again. It goes without saying, the Geyser should be on a timer, but the 5kW from the LA batteries could be just enough for 2 heating cycles (of which one is early morning). The final answer lies in what your daily/nightly draw from the Lithium bank + LA bank. e.g. 50% daily draw on Lithium = 15kWh * 0.5 = 7.5kWh + 2 cycles of 2h on LA = 4h * 1.5kw = 6kwh (LA batteries only use 50% in any case, else they get damaged, so already over limit!) = 13.5 kWh, Now add in your house consumption per day say ave. 10kwh. In Summer (Oct - March), one could have 8h of good sunshine (7:30 - 3:30). So the required PV to replenish the batteries & supply the load = 24kWh/8h = 4kW. You have 2 x 5 x 550W = 5500W maximum. At 85% efficiency, that will give you +-4675W peak. Which is barely enough to cover everything, never mind a few hours a cloud etc. If you use much less that in the calcs above, you might have some margin. You might need to adjust settings of the geyser timer to find a good middle way. Good Luck. Quote Link to comment Share on other sites More sharing options...
man0war69 Posted October 7 Author Share Posted October 7 thank you for your reply. Changeover switch from inverter to eskom for the geyser invert is a great idea which i have not included. I do have a changeover switch on the growatt parallel inverter setup. Also have a timer on the geyser currently as which i'll set to only charge the geyser batteries during optimum sun times. Yes i realize that with the additional load of the geyser inverter drawing indirectly from the panles i may need to add some more panels on. I have added another lithium 150ah battery to my growatts so now have 3 x 150ah batteries to leave some wiggle room. They get fully charged by around 10:30 AM on a nice sunny day and around 12:00 on a cloudy day. Adding the extra load of chrging the additional batteries for the geyser may require additional pannels. I will try out with a simple 15amp charge first and see how that does to charge up my geyser batteries and increase charge current as required. I am planning on adding another 6 panels (3 x 550w to each of the two strings) before winter comes around. Problem i forsee with winter is less and weaker sun hours per day and more power used. Quote Link to comment Share on other sites More sharing options...
Sidewinder Posted October 7 Share Posted October 7 Summer vs Winter is something you need to evaluate before adding more panels. Winter = more consistent, but slightly less production. Summer, higher production, but frequent lower days, especially in Jan. That's if you are in Gauteng. WC is much worse in Winter. Some graphs to illustrate Quote Link to comment Share on other sites More sharing options...
GMAC Posted October 7 Share Posted October 7 Why not just buy an geysertech Pi2R micro geyser solar unit and install 3+ panels to it . Quote Link to comment Share on other sites More sharing options...
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