A windturbinecontroller for charging batteries needs to have 3 main functions:

- 3 phase rectifier: to convert the 3-phase AC into DC for the battery, a diode bridge is needed:

- charge controller: the battery needs to be charged at the correct voltage (13,5V-14,5V)

- discharge controller: deep discharge damages the battery, so it has to be switched off at the appropriate level (around 12,6V unloaded at room temperature).

- dump load: when the battery is full, the rest of the power needs to be diverted to prevent overcharging the battery. The most common application is to dump it into resistors. Just disconnecting with a switch is not enough as it would make the windturbine runaway with a too high RPM, leading to self-destruction.

We designed our own controller to provide these functions, on the very handy website of schematics.com. (We are not affiliated)

Although this controller worked fine, it set's you back 25EUR in parts, labour not included. That is if you don't make any mistake..  Therefore the cheap (Asian) controllers we mentioned in our previous post are also worthwile looking into. There are a lot of deviations of the same controller to be found on marketplaces like Alibaba, Amazon, Ebay,.. Often relabeled with a fancy brandname and then sold for twice or even quadruple the original price.

We ended up buying this one for only 10,89EUR on Amazon.de: "Zerodis Wind Charge Controller Wind Regulator Charge controller with self and hand brake function Waterproof 400W (12V)". With the use of the Google Translate app and some basic reasoning we were able to understand the labeling and how the controller works:

It works fine and even has a button to manually control the braking (=dump load) for maintenance.

Another controller that came in was the "Zerodis 12V / 24V 300W wind turbine generator lader controller". It's named Zerodis, but actually it was just  the cheapest rebrand we could find, underneath it's all Chinese. It came in for 28EUR, and there is clearly a quality difference: the cables are thicker, and the heatsink of the dump load is also way bigger dimensioned.

It works just fine (for now?) and runs cooler than the other controller thanks to the bigger heatsink.

Unfortunately, none of these commercial controllers have a function that protects the battery agains overdischarge. Therefore we added an additional unit, bought seperately for around 10EUR on Amazon:

It does the job but relates battery charge only to the battery voltage. This means that if you connect a high power load, the voltage also drops, triggering a false 'empty battery' alarm. There are more intelligent discharge controllers on the market or to be made, that also measure the current that the load is drawing, but these cost a multitude of the price.

This is how it looks like al wired together. (The 3-phase current from the windturbine comes in through the thick black cable)