Off-Grid CyboInverter Q&A  
  An on-grid solar system is simple. Its goal is to send power to the grid. An off-grid solar system is much more complex since the applications can be so different. In this section, we describe several "simple-to-adopt" applications, which can help users and installers design and install off-grid solar systems.  
1 How do I design an off-grid solar power system in general? Is it dependent on the AC loads? Yes. It depends on the AC loads, as well as the wattage required, daily usage, and days of autonomy, etc.

Due to the complexity and requirement variations, CyboEnergy has published a Solar Power Microgrid Design Guide, which can be downloaded from the homepage of our website at:

Please refer to the Microgrid Design Guide to better understand your solar application and general design rules.
2 Should I design multiple off-grid AC circuits based on the loads? Yes. This is very important. In general, it is important to have multiple off-grid AC circuits:
  1. Have an off-grid AC circuit to run small and sensitive loads such as lights, fans, TV, radio, CD player, computer, cel phone charger, etc. These devices require pure sinewave AC.
  2. Have a separate off-grid AC circuit to run the heavier and problematic loads such as old-fashion refrigerators, which require a lot of surge power to start the compressor.
For the same reason, like in our homes, there is a branch circuit for the refrigerator, a branch circuit for the washer and dryer, a branch circuit for the electric stove, and many branch circuits for the other loads that do not require a lot of power.

In a U.S. single family home, there are many 20A branch circuits with 240V in the electric service panel. The power of a 20A circuit is limited at about 4KW. Then, each AC outlet has only 120V AC. So, each AC outlet can provide about 2KW.

In conclusion, you should offer 1KW or 2KW off-grid circuits to make things simple for most applications.
3 How do I design a microgrid for rural schools? I'm using loads like: lights, fans, computers, etc. The design rule described in Q&A 2 applies to this case well. For instance, the school needs a total 10KW power. It is a good idea to have 10 x 1KW off-grid circuits. Each 1KW circuit can power lights and computers for multiple class rooms, depending on the total power required.
4 How do I design a microgrid for rural hospitals and clinics? I'm using loads like lights, fans, small medical equipment and a fridge to save vaccines. The design rule described in Q&A 2 is applicable to this case.
  1. Have an off-grid AC circuit to run small and sensitive loads such as lights, fans, TV, small medical equipment, PC, cel phone charger, etc. These devices require pure sinewave AC.
  2. Have a separate off-grid AC circuit to run the refrigerator which may require a lot of surge power to start the compressor. Batteries are needed to supply DC power to the CyboInverter in order to keep the refrigerator running 24/7.
5 Our application site can install 10KW solar power. Can off-grid CyboInverters be used for this application? Yes. Based on the rules described above, please design multiple off-grid circuits to provide proper amount of power to run the loads. For instance, we may have 10 x 1.2KW off-grid systems, or 5 x 2.4KW off-grid systems, or a combination of the two.
6 Why can't you offer a 10KW off-grid solar power circuit? Unless you have a load that needs this much power, it is a good idea to separate the 10KW system into several smaller 1.2KW or 2.4KW off-grid systems. On the other hand, a CyboInverter Multi-Pack with one Master Unit and several Slave Units can support a larger off-grid circuit. For instance, a 7.2KW off-grid AC circuit can be built with 1 CyboInverter Master unit and 5 Slave units. (1.2KW x 6 = 7.2KW).

For more information on CyboInverter Multi-Packs, download the spec sheet here.
7 How long does it take to fully charge three deep cycle batteries? How long does a fully charged battery provide power, especially at night and during rainy weather? The size of a battery is based on Amp Hour (AH). Think of battery as a pool of water. Current is like water flow. AH is running water for a period of time in hours.

As an example, when 3 x 12V 50AH batteries are connected in series, it becomes a 36V 50AH battery set. It can deliver 250W DC power for about 7 hours.

Calculation: 250W DC power from the 36V battery set runs at about 250W / 36V = 7A. So, 50AH / 7A = 7 hours.

The 4A version of CyboCharger can charge batteries at 4A. So, to fully charge a 50AH battery, it requires about 12 hours.
8 What are the key advantages and benefits of using off-grid CyboInverters compared to traditional off-grid solar systems? The key unique advantages of off-grid CyboInverters include the following:
  1. Most off-grid inverters on the market need to have batteries as DC inputs. The off-grid CyboInverter can take DC power from solar panels directly, therefore, does not require batteries to run. This is well suited for PV solar heating, solar cooking, solar EV charging, and applications that do not need power in the evening.
  2. An off-grid CyboInverter has 4 input channels, each of which can be connected to a solar panel or battery. It can automatically detect if the connected DC source is a solar panel or a battery. If it is a battery, the CyboInverter will enable battery low voltage disconnect (LVD) function to protect the battery from over-discharging.
  3. If there is sufficient DC power from the solar panels, the CyboInverter will not draw power from the connected battery set thereby saving the battery life.
  4. Due to the flexibility of the multiple input channel design of the CyboInverter, the battery size can be reduced and the battery life extended.

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