I am having difficulty in understanding one control box which is used to charge the battery using solar and wind energy as well as power the load at the same time. I have attached the picture below enter image description here

I understand the part of the wind turbine but what I don't understand is the part where it shows the positive terminal of solar panel, battery and load should be connected together. How can this work? since the battery is charging (connected to solar panel) as well as discharging (connected to load) at the same time?

In my mind I was thinking the controller would be more like this the following, enter image description here, here you have separate connection point for each components which make sense to me but in my previous picture I don't understand. Can any one answer this for me.

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    \$\begingroup\$ Quite possibly the controller is switching using the negative. This might also avoid any arcing as well. \$\endgroup\$ – Tim Spriggs Mar 30 '16 at 14:24

Very crudely it will look like this:


simulate this circuit – Schematic created using CircuitLab

How it works

  • D1 to 6 rectify the three-phase current from the turbine to feed the "DC bus". If the turbine is running or voltage output from it is low D1 to D6 will be reverse biased and the battery can't discharge through the turbine windings.
  • The panel also feeds power into the DC bus. I've shown D7 to prevent discharging the battery through the panel. In practice it will be more complicated than that if the system optimises the power transfer from the panel.
  • SW1 and 2 can be switched by the controller to regulate voltage or power to the load and the battery charging current. Again, this is highly simplified but you would expect the controller to prioritise the load if input power is low and charge the battery when possible. When input power is lower than the load the battery will supply power. When battery voltage drops to a preset low limit the load should be automatically disconnected.

The same design could be achieved using your terminal arrangement and connecting all the '+' terminals internally. They saved two terminals doing it this way!

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  • \$\begingroup\$ Thanks a lot this is quite clear but I still have one question. What happens to the power generated from the solar and wind when battery is powering the load? Can the battery be charged when it is being used to power the load? \$\endgroup\$ – Electronic Curious Mar 31 '16 at 18:24
  • \$\begingroup\$ Think of the battery as a reservoir, the wind and solar as pipes filling it and the load as a drain on the reservoir. The reservoir level will rise if the the inputs exceed the outputs. The reservoir level will fall if output exceeds inputs. To answer your question: when the wind and / or solar input rises above that of the battery they will power the load and charge the battery. As their output falls the battery charge will cease. When it falls below battery voltage then the battery takes over the load. \$\endgroup\$ – Transistor Mar 31 '16 at 18:56
  • \$\begingroup\$ I understood so now I am thinking of something. If I have a very big battery capacity (lets say >600Ah, 12V) and if it connected to the controller (same as in my first picture) then is it possible to connect a load which draws a big amount of current (lets say 20A at 12V)? Does this output depends on what kind of controller you use? or can I just connect any load as long as its within the battery range? I assume it does right? since controller is switching between the battery and the load so it should be able to handle the output power. \$\endgroup\$ – Electronic Curious Apr 1 '16 at 7:28
  • \$\begingroup\$ Yes, the controller must have a maximum current that it can handle. Check the manual. \$\endgroup\$ – Transistor Apr 1 '16 at 8:31
  • \$\begingroup\$ I checked the manual and it says it can deliver max 10A at 24V but I need 25A of current to power my load at 12V. I cannot connect my load directly to the load connection point, so is there a way how i can power my load with also charging the battery with solar and wind energy. Is it an idea to connect something (some kind of storage, UPS) in between load and the battery to power the load? \$\endgroup\$ – Electronic Curious Apr 4 '16 at 7:32

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