My Off-Grid Life Experiences

6 months ago, I installed an off-grid SPP in my own house. I am an electrical and electronic engineer who has already worked in the renewable energy sector for many years in areas such as design, project, field, maintenance and repair. For the first time, it was a good experience to finish the installation process from A to Z by myself.

I chose a 5kWh, 48V, LiFePO4 Battery because I foresee a modest electricity consumption. I expect a minimum of 6 years of life and performance from the Lithium Iron Phosphate battery. Although it is more expensive than other battery types, I chose this type of battery due to the difference in life. I expect an average DOD rate of 80%, an average operating temperature of 35 degrees Celsius in summer and 20 degrees Celsius in other months. Under these conditions, theoretically, a performance of more than 5 years can be expected.

6 months ago, I installed an off-grid SPP in my own house. I am an electrical and electronic engineer who has already worked in the renewable energy sector for many years in areas such as design, project, field, maintenance and repair. For the first time, it was a good experience to finish the installation process from A to Z by myself.

I chose a 5kWh, 48V, LiFePO4 Battery because I foresee a modest electricity consumption. I expect a minimum of 6 years of life and performance from the Lithium Iron Phosphate battery. Although it is more expensive than other battery types, I chose this type of battery due to the difference in life. I expect an average DOD rate of 80%, an average operating temperature of 35 degrees Celsius in summer and 20 degrees Celsius in other months. Under these conditions, theoretically, a performance of more than 5 years can be expected.

For this battery power, I preferred 5 pieces of 560W, Monocrystalline, Half Cut solar panels. Since it is a forest area, tree shadows fall on the panel at various times of the day and since it is also in the forest, I especially preferred half-cut in case of foreign objects on the panel. (Series with 5xx Wp may not be optimum for homes due to their size)

For the inverter, I preferred the Growatt New Energy 5000ES model, which I liked its features in off-grid. The reason why I especially preferred this series is its ability to work with both Lithium batteries and lead acid batteries. In addition, the ability to work with and without BMS, customization of working conditions, and the ability to work with the grid are the features I like the most.

The only problem I had after installation and testing was the communication between the battery and the inverter. I could not provide communication, but then I decided not to use the communication feature to turn it into an experimental environment. Growatt New Energy allowed to adjust the Charge Voltage, Float Voltage and Cut-off Voltage settings. For this reason, I experimented with these voltage values. BMS communication is still not active.

One of the problems I had during use was that the system was completely cut-off. By default, the battery voltage is 42V, so when the charge is over, the inverter continues to energize until the battery shuts itself off, the voltage drops to a critical level and the system completely shuts down. I had to connect an external power supply to wake it up again. Afterwards, when I set the min voltage to 47V, there was no problem because the inverter was shutting down the system before the battery turned itself off. So when the sun came out again, the charging process started.

Here I am surprised that Growatt does not wake up again without battery, even though there is sun. It does not turn itself on without seeing the battery. (Note: Off-Grid inverters, especially cheap models, usually fail if the panel is connected before the battery).

I have two risky months in terms of design, December and January. Since the insolation is very low in these months, and there may be times when the sun does not shine for days, energy security is at risk. I don't plan to upgrade to battery only for this situation. Instead, I plan to solve emergencies with a little more control and a small generator if necessary.

To improve battery performance, I set the charging current to 20A (1kW instantaneous). Therefore, although the panel power goes up to 2.8kW, the power transfer is limited to 1kW. Except for December-January, there is no fast charging request in a short time. Especially in this season, there is no change whether it fills the 5 kWh battery in 5 hours or 1 hour. (It can also meet AC energy needs while charging.)

However, I advise ordinary households who are not familiar with all these issues to use a minimum of 10 kWh battery. 5kWh battery may cause problems a few times a year, but if you are far from the subject, you may have serious problems...