In my previous instructables I described the details of energy monitoring of a off grid solar system.I have also won the 123D circuits competition for that.You can see this ARDUINO ENERGY METER.
Finally I post my new version charge controller.The new version has automatic battery voltage selection for 6/12 v .Automatically charge set point according to the battery.No need to change any hardware as well as software for 6V or a 12 V system.Solar panel up to 100w/12v can be used.You can see it by clicking the following link.
In solar power system, charge controller is the heart of the system which was designed to protect the rechargeable battery .In this instructables I will explain the PWM charge controller.
In India most of the people are living in rural area where national grid transmission line is not reached till now.The existing electric grids are not capable of supplying the electricity need to those poor people.So renewable energy sources ( photo voltaic panels and wind-generators) are the best option I think. I know better about the pain of village life as I am also from that area.So I designed this DIY solar charge controller to help others as well as for my home.You can't believe, my home made solar lighting system helps a lot during the recent Cyclone Phailin.
Solar power have the advantage of being less maintenance and pollution free but their main drawbacks is high fabrication cost, low energy conversion efficiency. Since solar panels still have relatively low conversion efficiency, the overall system cost can be reduced using a efficient solar charge controller which can extract the maximum possible power from the panel .
What is a Charge Controller ?
A solar charge controller regulates the voltage and current coming from your solar panels which is placed between a solar panel and a battery .It is used to maintain the proper charging voltage on the batteries. As the input voltage from the solar panel rises, the charge controller regulates the charge to the batteries preventing any over charging.
Types of Charge controller :
The most basic charge controller(ON/OFF type) simply monitors the battery voltage and opens the circuit, stopping the charging, when the battery voltage rises to a certain level.
Among the 3 charge controllers MPPT have highest efficiency but it is costly and need complex circuits and algorithm.As a beginner hobbyist like me I think PWM charge controller is best for us which is treated as the first significant advance in solar battery charging.
What is PWM:
Pulse Width Modulation (PWM) is the most effective means to achieve constant voltage battery charging by adjusting the duty ratio of the switches ( MOSFET ). In PWM charge controller, the current from the solar panel tapers according to the battery’s condition and recharging needs. When a battery voltage reaches the regulation set point, the PWM algorithm slowly reduces the charging current to avoid heating and gassing of the battery, yet the charging continues to return the maximum amount of energy to the battery in the shortest time.
Advantages of PWM charge controller :
1. Higher charging efficiency
2. Longer battery life
3. Reduce battery over heating
4. Minimizes stress on the battery
5. Ability to desulfate a battery.
This charge controller can be used for :
1. Charging the batteries used in solar home system
2. Solar lantern in rural area
3. Cell phone charging
I think I have described a lot about the background of the charge controller.let starts to make the controller.
Like my earlier instructables I used ARDUINO as the micro controller which include on-chip PWM and ADC.