# Small Wind turbine with MPPT and Battery Charging

#### jacko91

Joined Mar 12, 2020
1
Good day,

I am starting to put together a wind turbine project (roughly 50W, so very small).
I still have some generall hardware design questions:
Different Setups:
1) Easiest Setup:

Let's say there is an diode between Rectifier and Battery to prevent current flow from battery toward the turbine. My understanding is that the turbine will start turning and generating voltage. As soon as the turbine exceeds 12V, current starts to flow from the Generator to the battery. If the turbine would be without any load, the voltage would increase with more wind. But as the battery is connected increasing current will prevent the turbine from turning fast, right? So as long as the turbine is spinning fast enough the battery will be loaded till it will be destroyed, right? (I know that this setup is not a good one, just for understanding everything)

2) DC/DC converter:

I have seen setups where there is an additional DC/DC converter. I guess the idea is that the converter converts the voltage to the desired loading voltage of the battery. And depending if it is boost or buck or both it can already start loading the battery if the generator produces less than 12V. I am still having trouble to grasp the behaviour of the generator voltage if it exceeds 12V. As far as I am concerned, it should behave the same as setup 1) if 12V are exceeded, right?

3) MPPT:

A MPPT (maximum power point tracking) is used to adjust the generators voltage to the maximum power outcome from the turbine. Here is still my biggest questionsmark. Lets say the buck/boost converter is driven via pwm from a microcontroller with some mppt logic inside. To my understanding the pwm will be adjusted inorder to optimize U*I (voltage*current) coming from the rectifier. Adjusting pwm will effect the output voltage of the converter and thus the inputcurrent and inputvoltage of the converter, right? But how will adding a battery effect all this. If the mppt adjusts the output voltage to 20V for example to optimize the generator output, then putting a 12V battery on 20V is not a good idea, right?

Hope this is all not too confusing.

Thanks for your time and patience.

Greetings

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#### nsaspook

Joined Aug 27, 2009
8,278
Obviously the MPPT function will be deactivated when it's required to protect the battery from over-voltages from the required voltage limit to correctly recharge the battery. If the battery can accept MPPT generated charging current (Bulk) at a source voltage less than the voltage limit, the converter will remain in MPPT mode. As the MPPT charging voltage in the voltage*current product exceeds the set battery voltage limit (Absorption) the converter will drop out of MPPT.