Step 8: Build the charge controller

Picture of Build the charge controller
Now That I had all the mechanical parts sorted out, it was time to turn toward the electronic end of the project. A wind power system consists of the wind turbine, one or more batteries to store power produced by the turbine, a blocking diode to prevent power from the batteries being wasted spinning the motor/generator, a secondary load to dump power from the turbine into when the batteries are fully charged, and a charge controller to run everything.

There are lots of controllers for solar and wind power systems. Anyplace that sells alternative energy stuff will have them. There are also always lots of them for sale on Ebay . I decided to try building my own though. So it was back to Googling for information on wind turbine charge controllers. I found a lot of information, including some complete schematics, which was quite nice, and made building my own unit very easy. I based my unit on the schematic of the one found on this web site:


That web site goes into a lot of detail about the controller, so I'm only going to talk about it in fairly general terms here. Again, while I followed their general recipe, I did do some things differently. Being an avid electronics tinkerer from an early age, I have a huge stock of electronic components already on hand, so I had to buy very little to complete the controller. I substituted different components for some parts and reworked the circuit a little just so I could use parts I already had on hand. That way I had to buy almost nothing to build the controller. The only part I had to buy was the relay. I built my prototype charge controller by bolting all the pieces to a piece of plywood, as seen in the first photo below. I would rebuild it in a weatherproof enclosure later.

Whether you build your own, or buy one, you will need some sort of controller for your wind turbine. The general principal behind the controller is that it monitors the voltage of the battery(s) in your system and either sends power from the turbine into the batteries to recharge them, or dumps the power from the turbine into a secondary load if the batteries are fully charged (to prevent over-charging and destroying the batteries). The schematic and write-up on the above web page does a good job of explaining it. Much more information on building the charge controller, including larger and easier to read schematics, can be found on my web site at http://www.mdpub.com/Wind_Turbine/index.html

In operation, the wind turbine is connected to the controller. Lines then run from the controller to the battery. All loads are taken directly from the battery. If the battery voltage drops below 11.9 volts, the controller switches the turbine power to charging the battery. If the battery voltage rises to 14 volts, the controller switches to dumping the turbine power into the dummy load. There are trimpots to adjust the voltage levels at which the controller toggles back and forth between the two states. I chose 11.9V for the discharge point and 14V for the fully charged point based on advice from lots of different web sites on the subject of properly charging lead acid batteries. The sites all recommended slightly different voltages. I sort of averaged them and came up with my numbers. When the battery voltage is between 11.9V and 14.8V, the system can be switched between either charging or dumping. A pair of push buttons allow me to switch between states anytime, for testing purposes. Normally the system runs automatically. When charging the battery, the yellow LED is lit. When the battery is charged and power is being dumped to the the dummy load, the green LED is lit. This gives me some minimal feedback on what is going on with the system. I also use my multimeter to measure both battery voltage, and turbine output voltage. I will probably eventually add either panel meters, or automotive-style voltage and charge/discharge meters to the system. I'll do that once I have it in some sort of enclosure.

I used my variable voltage bench power supply to simulate a battery in various states of charge and discharge to test and tune the controller. I could set the voltage of the power supply to 11.9V and set the trimpot for the low voltage trip point. Then I could crank the voltage up to 14V and set the trimpot for the high voltage trimpot. I had to get it set before I took it into the field because I'd have no way to tune it up out there.

I have found out the hard way that it is important with this controller design to connect the battery first, then connect the wind turbine and/or solar panels. If you connect the wind turbine first, the wild voltage swings coming from the turbine won't be smoothed out by the load of the battery, the controller will behave erratically, the relay will click away wildly, and voltage spikes could destroy the ICs. So always connect to the battery(s) first, then connect the wind turbine. Also, make sure you disconnect the wind turbine first when taking the system apart. Disconnect the battery(s) last.
AnAnalyst2 years ago
While your charge controller will charge batteries, it has no topping charge circuitry. Because of that, your batteries will not last as long as they could. Given that they are a major expense, it may be worth while to buy a commercial one or add the necessary circuity.
acicalla3 years ago
I have a question regarding the 99v ametek motor and charge controllers. So far I have only been able to find charge controllers that accept 12, 24 and 48v dc as input from either a wind turbine or solar panel. So what if anything needs to be done to step down the voltage from 99v to 48v dc to the charge controller? Or do I even need to change anything? Can I just wire the 99v ametek dc output to the 48v charge controller?
Unless you gear it up, your 99v Ametek will only be producing 30v MAX at wind turbine speeds. A 12v charge controller will handle this easily.,
TheGreatS3 years ago
Here is an easy yes or no question. Will the char controller work for any motor of any voltage rating? Mine is a 120 volt DC motor salvaged from a blender (If that helps any).
LIS101143443 years ago
hi i can get hold of a pillar drill easily, it is rated 1420 rpm and 240 volts,
so 1420 divided by 240 =5.92 rpm - per volt
would this be a good motor/generator for a wind turbine?
LIS101143443 years ago
hi just wondering, if a motor is producing a DC current to charge a battery then is there any need for a rectifier/bridge rectifier to stop the charge from the battery reverting to powering the motor?
mdavis19 (author)  LIS101143443 years ago

If you look closely at the captions in the photo of the charge controller, there is a blocking diode to prevent the battery from back-feeding the motor. There are also rectifier diodes in the schematic of the charge controller.
pantaz3 years ago
The charge controller has been redesigned by the original designer. Reduced part count, and easier to find components! 


 He also has kits and assembled units available (see link on his website). 
I have a 1000 watt generator and the engine leaks oil when it is started or running. I was thinking of removing the generator portion and using it with some sort of a turbine setup.

I have not thoroughly inspected the current setup on this generator and do not know if it is a DC or AC generator although it has ports for accessing DC along with the AC outlets.

How hard would it be to utilize everything already included in the parts on this generator?
Dear Friend I read your article and imediatly went to my old motors box. I knew I had a couple of those AMETEK motors, they came from I don't know what I save from the trash I saw on the street, I hooked up a 12volt led bulb to it and just with a hand spin with the shaft , it almost burned the bulb, so I decided to do your project, I will post pictures as soon as I have something done
Great Project
Diogo Monteiro
From: Sassoeiros, Portugal
Q1 should be substituted with a 2N7000. An IRF540 is total overkill for switching a relay coil. The IRF540 is powerful enough that it might be used instead of a relay. Check the milliamp draw of the relay coil and use an appropriate transistor.  You could save like $5 that way.
Could this controller design be modified for 48v systems?
cherwa5 years ago
you are using a  lm 7808 to get 8 volts to power a 4001 quad nor gate. i dont own CMOS, but i do have TTL chips.
would it be alright if i used a 5V voltage regulator and a TTL 7404 quad nor gate?
If i can does anyone know what the LM1458 CMOS chip is in TTL?
Can Some one find a list of the parts needed for the charge controller? That would be AMAZING!
razzor1116 years ago
where can I get plans to build a inverter and how do I keep the voltage down to 14.5 VDC my generator will put out 35VDC at low RPM
cowen razzor1115 years ago
Voltage regulator

There was a project in Poplular science or something like that back in the 90s called

Tin Lizzy

It was a crude inverter.  The plans use a few resistors, a transistor, and the basics of stepping up power from 12 V DC to AC using transformers.

I built that and worked great in my car before the transisor versions.  I am loking for the plans again.  The parts were all from Radio Shack and if you touched out puts would give you a nasty shock.

Wattage was low as I remember.

I would like to see a build on here using transformers instead of transistors.  Any one?

One Idea I have used was an OLD APC battery backup wire the battery leads to your supply.  these are from 12 V, 24 V or 48 V models so look at how the batteries are setup and what the voltage of those packs are.
xetero5 years ago
can I use washing machine motor or ceiling fan or electric fan motor?
ccarl5 years ago
 can anybody help me here is my email add: ccarl@eudoramail.com
ccarl5 years ago
 pls help me with my first wind generator ..i just want to ask if i can use the 12v car regulator to charge my battery my motor is 24v ametek .
Andruha11236 years ago
why would u dump electricity? just connect a bulb and have a light or something.
over charging batteries ruins them, although there could be a better use for the excess.
wildman296 years ago
what about an automotive alternator it can put out up to 100 amp's on the average vechicle . might simplify charge controlling. you would just have to convert voltage . note the alt needs voltage to entice its charge circuit . im gonna build one of these i'll let ya's know how it goes !!
Have you tried using your alternator already? i also heard about their current output. But when i opened the hood in my car, the alternator has to go fast to output that kind of current and voltage.
snake2106036 years ago
hi,i want to know something,what does the charge and dump button do?
snake2106036 years ago
hi friend,your design and idea is very interesting.in fact i am building a wind generator too with gearing system due to the high rpm of the motor.i needed a charge controller,so i tried to build it from your schematic but i am having great difficulty in mounting the electronic components.can you please help me out.thanks
tubajoey16 years ago
about how long did it take you to complete this step? i am going to try to make a wind turbine, based on your instructions, and hopefully be able to run everything in my room. thanks