Charger Controllers

The purpose of a charge controller is to prevent the batteries from being overcharged or completely discharged. This is the key to battery longevity; do not overcharge, unless during equalization, or completely discharge the battery. Charge controllers monitor the current going to the batteries and when the batteries are charged, the controller will limit the current being sent to the battery bank. Also, it is good to choose a good controller which will provide a float current to keep the batteries fully charged.

Choosing the Proper Controller

For the most part, all controllers are rated by their ability to handle certain amounts of current. The ideal is to choose a controller that is rated to take 1.25 times the current that your solar array, or renewable energy system, produces. This provides a safeguard in case of slight fluctuations. Also, you have to take into consideration the possibility that you may expand your solar array in the future. Here are some of the important features you need to look for when purchasing a quality controller:

* Lightning protection
* Periodic equalization cycles
* Built in charge current and battery voltage metering
* Low battery disconnect to prevent complete battery discharge
* Overload protection
* Float charge capabilities; this allow batteries to remain fully charged
* Temperature compensation features

Battery Protection in Cold Environments

In various parts of the world, cold weather is a way of life for many PV users. In Canada , it is very important to choose a charge controller that can automatically start charging when the batteries reach a certain state of discharge. This is critical, because the state of charge directly influences at what temperature a battery can freeze. If a battery becomes too cold or freezes, permanent damage can occur and greatly reduce the longevity of your battery bank.

Maximum Power Point Tracking (MPPT)

This is another excellent feature for anyone who needs a controller; especially those who live in an area where you receive major climate changes. For example, those who live in Canada receive a warm, sun filled summer, but also experience a winter season where there is snow, cold weather, and the sun tracks a lot closer to the horizon. The innovation with this feature is that it can take a certain amount of voltage and convert it into current! This feature has greater importance with solar arrays that experience lower production during winter months than summer and for solar arrays that need to operate in cold temperatures. As the temperatures drop, a solar panel generates a higher voltage due to increased efficiency. The last sentence is of importance, because in a climate such a Alberta , Canada , where temperatures are cold, MPPT can help compensate for the low path of the Sun through the sky.

The old cliché, “you get what you pay for”, can be applied here. This technology is more expensive but it is superior.