Kickstarter – Technology Working Group – Design of a simple diversion charge controller

Why use a charge controller ?

In a classic installation of small wind turbine, the charge controller is directly connected to the electrodes of the batteries which constitute the DC-bus and it has two roles :

•  Ensure the best use of the battery by being as close as possible to the constant current constant voltage (CC/CV) charge method (more information in the regulator manual).
• Protect the wind turbine by making sure it will never freewheel and therefore spin at high speeds which could damage the machine. This is why a dump load is used rather than simply opening the circuit (this method is used when using solar panels).

So, the controller “watches” the battery voltage until it reaches a certain voltage (called topping or absorption voltage). When it happens, the regulator starts sending some current to the dump load. As the battery is increasingly being charged, the current in the resistor increase, and so the current sent to the battery decrease. This way, its voltage remains constant.

You want to participate ? Here are different approach on how to improve the existing regulator :

• Further testing of the existing prototype : It would be nice to test the existing prototype in a large setting of different installations and particularly to measure the ability of the prototype to dissipate heat. If you installed a prototype and had a problem with it, please report it on the forum.
• Equalization : The existing prototype doesn’t take into account the equalization of the batteries. The equalization consists into forcing the battery voltage to a high level during a few hours once every months. This concerns the open lead acid batteries and helps to expand their lifetime. It could be interesting to add this feature to the existing regulator.
• Deep discharge protection : It could be interesting to find a solution to avoid deep discharge of the battery bank by disconnecting the load if the state of charge is too low. Any good idea for this is welcome !
• Temperature correction : For installations where the temperature varies a lot, it is interesting to be able to change the setting of the topping voltage
• Translation of the manual : You want to translate the manual into your language ? Please feel free to do it and post the translated text on the forum.
• Design of a prototype for 12 V installation : A circuit has been designed for 12 Volts installation (Circuit available here). It could be good to design a PCB for it, test it and improve it.
• Numeric design : The creation of a numeric design for a new charge controller could be interesting to add more features to it, although it might be less robust. If you are interesting into designing such a controller, you can download a first attempt at designing one here.

If you have any question, remarks about the design, if you want to report a malfunction or share your improvements on the device, please consult the forum or contact the coordinator.

Regulator for grid tied system

Hugh Piggott original generators are designed in 12 V, 24 V and 48 V for battery systems and until 350 V for grid connection. But recently inverters for grid connection with DC voltage range of 60 V to 80 V made possible the use of the 48 V generator for grid connected systems, achieving the lowest cost for systems up to 700 W. During normal operation, grid-tied inverters are able to control the DC bus voltage and be programed to extract the optimal current, tracking the maximum power point of the turbine. Although, it can loose it’s synchronization due to voltage dips, abnormal grid frequency or disconnection of the grid. During these situations the wind turbine turns freely, in high speeds that can damage the turbine, and generates high voltages that can be harmful for the inverter. Dump load controllers are designed in order to ensure a safe operation of the wind turbine and prevent the over voltages in the inverter. By connecting a Dump Load on the DC side, the turbine’s speed is limited as well as it’s generated voltage.

It is possible to find many commercial dump load controllers in the range of 350 V, but there is a lack in the range of 80 V. That’s why a regulator for the installation of this kind of installation has been designed.

You can download the Kicad files of the circuit and an explicative document on this regulator.

If you want to help on the design of this regulator, have a question or a remark please contact the coordinator