FBJ Posted June 3, 2022 Share Posted June 3, 2022 Hi. I'm looking for users who are exporting to grid and have batteries with their solar PV and Sunsynk hybrid inverter. I'd like to compare how it prioritises power flow. I'm curious to see if the inability to programme the following merit order under any combination of parameters is affected by battery types: Load; then Battery; then Export Please can you advise what battery you're using and share your System1 and System2 settings page and your System Flow Chart in a scenario where your battery is not yet full and you have excess solar. If you find you are exporting and charging at the same time, then please also provide the System Flow Chart when you've turned off export. Many thanks! My example is attached. I have a BSL 5.12kWh battery: Quote Link to comment Share on other sites More sharing options...
P1000 Posted June 3, 2022 Share Posted June 3, 2022 I'm guessing the clue is in the 54.59V. The battery asks for 54.5V, so it seems that it is "overcharging" the battery when you don't export. That might not be the whole story, though. Why do you want to charge your battery so fast? Quote Link to comment Share on other sites More sharing options...
FBJ Posted June 3, 2022 Author Share Posted June 3, 2022 5 minutes ago, P1000 said: I'm guessing the clue is in the 54.59V. The battery asks for 54.5V, so it seems that it is "overcharging" the battery when you don't export. That might not be the whole story, though. Why do you want to charge your battery so fast? Hi. Thanks - maybe I should check the battery voltage settings. Why I want to charge battery like that is because of the relative value of the kWh (in Cape Town municipality): 1) Load: R2.40/kWh for every load unit saved 2) Battery: R2.10/kWh for load served by battery after battery efficiency 3) Export: R1.01/kWh for export Quote Link to comment Share on other sites More sharing options...
P1000 Posted June 3, 2022 Share Posted June 3, 2022 11 minutes ago, FBJ said: Hi. Thanks - maybe I should check the battery voltage settings. Why I want to charge battery like that is because of the relative value of the kWh (in Cape Town municipality): 1) Load: R2.40/kWh for every load unit saved 2) Battery: R2.10/kWh for load served by battery after battery efficiency 3) Export: R1.01/kWh for export You need to also subtract your battery cost per kWh - purchase price/(expected cycles * kWh per cycle). I would bet that exporting makes more sense financially if you factor that in. Quote Link to comment Share on other sites More sharing options...
FBJ Posted June 3, 2022 Author Share Posted June 3, 2022 (edited) 51 minutes ago, P1000 said: You need to also subtract your battery cost per kWh - purchase price/(expected cycles * kWh per cycle). I would bet that exporting makes more sense financially if you factor that in. Fair point, @P1000 - that would subtract some R1.09/kWh at stated lifetime cycles (which makes it exactly match the export value! ;-). However, the value is back-ended in the extension of life so when valuing it today, with some discounting for time, it makes more sense for me to sweat the battery asset now and make it earn its payback asap. In any case, do you happen to have sight of any Sunsynk battery and export behaviour per chance? And/or advice on the correct battery voltage settings in the inverter for a BSL 5.12? (I currently have float voltage 54.8V, absorption voltage 55.0V). Many thanks. Edited June 3, 2022 by FBJ Quote Link to comment Share on other sites More sharing options...
P1000 Posted June 3, 2022 Share Posted June 3, 2022 If the battery is connected with the comms cable, the BMS will override the settings. FBJ 1 Quote Link to comment Share on other sites More sharing options...
Pumba Posted June 3, 2022 Share Posted June 3, 2022 In CT over a year you have to be a net user of the municipal kWhrs so I see no point in exporting to the grid. WannabeSolarSparky 1 Quote Link to comment Share on other sites More sharing options...
GreenFields Posted June 3, 2022 Share Posted June 3, 2022 4 hours ago, Pumba said: In CT over a year you have to be a net user of the municipal kWhrs so I see no point in exporting to the grid. Not sure I follow. Anywhere in the country you are not allowed to be a seller of electricity on the grid, that is Eskom's legal right. If you trade energy with the municipality, then on balance you have to be a net purchaser. CT calculates this over a 1-year period, Nelson Mandela Bay does it over 1 month, and other municipalities could do it over different periods, I don't know. For argument's sake, rather than buy 10,000kWh in a year, maybe your grid-tied solar reduces your net purchase to just 1kWh, and you'd still be a net user. Only, if you end up exporting more than you import, you'd just never be paid out for it. The economics of using the grid as a "battery" might mean that you never get back as much as you put in, but that then has to be weighed against the cost of buying an actual battery. Quote Link to comment Share on other sites More sharing options...
FBJ Posted June 3, 2022 Author Share Posted June 3, 2022 1 hour ago, GreenFields said: Not sure I follow. Anywhere in the country you are not allowed to be a seller of electricity on the grid, that is Eskom's legal right. If you trade energy with the municipality, then on balance you have to be a net purchaser. CT calculates this over a 1-year period, Nelson Mandela Bay does it over 1 month, and other municipalities could do it over different periods, I don't know. For argument's sake, rather than buy 10,000kWh in a year, maybe your grid-tied solar reduces your net purchase to just 1kWh, and you'd still be a net user. Only, if you end up exporting more than you import, you'd just never be paid out for it. The economics of using the grid as a "battery" might mean that you never get back as much as you put in, but that then has to be weighed against the cost of buying an actual battery. The benefit is you get to make something off the PV power you can generate when you would otherwise have simply curtailed when your battery is full and you have surplus. See green area in bottom vs top of attached chart. Yes, the value will stack up differently for different setups. Quote Link to comment Share on other sites More sharing options...
Scorp007 Posted June 5, 2022 Share Posted June 5, 2022 On 2022/06/03 at 8:50 PM, FBJ said: The benefit is you get to make something off the PV power you can generate when you would otherwise have simply curtailed when your battery is full and you have surplus. See green area in bottom vs top of attached chart. Yes, the value will stack up differently for different setups. A great way of showing the waste of PV. If only we were not hit by an Admin fee which is not easy to overcome. Further even at a 50c per unit income for exporting to pay back the cost of a bi-directional meter can take many many years. Self consumption remains the name of the game and moving daily loads to the day time. Pumba and jasweb 1 1 Quote Link to comment Share on other sites More sharing options...
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