Once your solar panels are up and running, the next obvious requirement is some sort of charge controller, since continuous overcharging will ruin the expensive battery bank.

Charge controllers intended for solar panels work by monitoring the battery voltage, and once it reaches full charge, the controller simply short the solar panel leads together. This doesn’t harm the solar panels but it does waste whatever power they are generating. The energy ends us up heating the transistors in the controller instead.



Simple Charge Controller Circuit

Charge controller

In a typical charge controller for a solar panel, the incoming battery voltage is divided in half by a pair of 3.3K resistors, so the trip points are adjusted to one-half the desired levels. Start at 14 volts for the trip points. The actual trip points will depend on your particular batteries, but a good starting point is 14.5 volts for full charge, and 11.8 volts for discharged. In this case, the trimpots should be adjusted to read 7.25 volts at TP-A and 5.9 volts at TP-B.

You will probably need to monitor your battery voltage through several charge cycles to determine the perfect trip points for your system.



Simple Wiring Diagram Showing the Charge Controller and Batteries.

Wiring diagram for charge controller and batteries

You can easily buy a charge controller or build your own custom made if you know how. Certainly the best option is buy an already built controller as this is a critical part of solar panel energy system.

In our next post we shall discuss the main points on building the battery bank. Until then…

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Whether you build your own, or buy one, you will need some sort of controller for your wind turbine.

There are lots of charge controllers manufactured for solar and wind power systems. Any company that sells alternative energy stuff will have them. There are also always lots of them for sale on Ebay.

What’s a Charge Controller?

Basically, the general principle behind a charge controller is that it monitors the voltage of the batteries in your renewable energy system. The controller either sends power from your homemade wind generator into the batteries to recharge them, or diverts power coming from the wind generator to another place. This only occurs if the batteries are fully charged (to prevent over-charging and destroying the batteries).

We are assuming you are using a 12 volt battery system for the purposes of this discussion.

When your homemade wind generator is in operation, the wind generator is connected to the controller. Wires then run from the controller to the battery.

When you use power to run some appliance, say your TV, the power is then taken directly from the battery. If the battery voltage drops below 11.8 volts (you can set this on the controller), the controller switches the generator power to charging the battery. If the battery voltage rises to 14.5 volts (again, you have to set this), the controller switches to dumping the generator power into the dump load.

Usually, a water heater, or some other small device is used as a dump load. There are switches to adjust the voltage levels at which the controller changes between the two states of charging. A 11.8 and 14.5 volts as cut-in and cut-out voltages are recommended after consultation with battery experts.

There are two LED lights on the charge controller. When charging the battery, one LED is lit. When the power is being dumped to the other load the other light will be lit.

Usually the system runs pretty automatically and the LED lights gives us easy feedback on whether our renewable energy system is performing properly, and what it is doing right then. When the wind is really blowing more current goes into the batteries, which means more load on the generator. The system pretty much governs itself.

In a storm the force of the winds wind can get pretty dangerous. Switching the controller to dump power into the other load does a good job of braking the homemade wind generator and slowing it down.

Warning: the whole blade and hub assembly can swing around and knock you on the head if you are not very careful and the wind changes direction while you are working on it.

Next post: Wiring The Wind Generator. Stay tuned