How charge controllers work

All about Charge Controllers

The Charge Controller is a simple but very important appliance in your Solar System. It sits between the Solar Panel and the Battery. It has 3 basic functions but lots of other technical stuff is going on as well…

Monitor and control the Battery voltage
When the battery has its voltage reduces from its use it allows the Solar Panels to charge the Battery back to the required voltage.
Also when the Battery is at fully charged it stops any further charging. If you continued to charge the Battery it would eventually get hot and may set on fire or even explode.

Stops reverse current at night
At night without a Charge Controller is is possible current will flow back to the Solar Panel and effectively attempt to charge the Solar Panel with voltage.

12V DC Power      
You will see that many Charge Controllers have a DC power output. This is purely an extra power supply and the Charge Controller can handle both the DC power supply and charging the Battery. This is unlike a Wind Turbine Charging System where something needs to consume the electricity created and not used. 

There are two types of Charge Controller and you will read a lot about how one is the better that the other but both have there place and use in a PV Solar System.

PWM Explained
PWM stands for Pulse Width Modulation. PWM is often used as one method of float charging. It sends out a series of short charging pulses to the battery in a very rapid “on-off” switch style. The controller constantly checks the state of the battery to determine how fast to send pulses, and how long and wide the pulses should be.
When a Battery is fully charged it may just “tick” every few seconds and send a short pulse to the battery. Where a Battery is very low or even fully discharged it may almost be constant. This is known as full on.
PWM are best for low power systems. Eos Solar Solutions offer a range of PWM Charge Controllers.
One small downside of a PWM Charge Controller is that it can also create interference in radios and TV’s due to the sharp pulses that it generates. But the location of the Charge Controller to these products will eliminate this.

MPPT Explained
MPPT stands for Maximum Power Point Tracker and it is a high-frequency DC to DC converter.  It takes the DC input from the solar panels, changes it to high-frequency AC, and then converts it back down to a different DC voltage and current to exactly match that of the Solar Panel to the Battery.
MPPT’s operate at very high audio frequencies, usually in the 20-80 kHz range. The advantage of high-frequency circuits is that they can be designed with very high-efficiency transformers and small components. The design of high-frequency circuits can be very technical because of the problems with portions of the circuit “broadcasting” just like a radio transmitter causing radio and TV interference. Noise isolation and suppression becomes very important. But this can be engineered  out. 
MPPT Charge Controllers are good where the Solar Panel is a long way from the Charge Controller. This is because of the losses in voltage over the long length of wire. The MPPT Charge Controller can compensate for this.

EOS Solar Solutions offer a range of both PWM and MPPT Charge Controllers