7Ah Sealed Lead Acid Battery
For example if you want to glow a 20Watt LED then this battery will serves the purpose really well.Before go further, studying the articles related to battery basics, rechargeable batteries and non- rechargeable batteries would be fruitful. Here we will design a 7 Ah charger for this battery.
How to Charge a Battery
How much source voltage should be greater than the battery voltage to charge?
It’s not a single value that you can rely on. But an average value at which you can surely charge your battery without hesitation is 20% more voltage than the battery voltage.
To charge a 12 volt battery the charging source should be 14.4 volts. Now the question is that how to attain this volts. I will answer this question later.
When Should you Stop Charging?
During building a charger, the most important question comes in mind that when should I cut off the charging source. This is the very critical point during making automatic chargers because mostly batteries do not bear overcharging and their life drastically decreases due to overcharging. Before I answer this question first understand anot should be charge at C/10 current no matter how big the battery is.
For example in 100Ah battery, if the battery is fully discharged then it will take 10Amps from the 14.4 volts source and if the battery is fully charged then it will not draw any current from the source and at 50% charging it will draw 5amps from source.
Step by step details to build automatic charger for 7Ah 12 volt seal lead-acid battery through micro-controller
Note: In this article I will give detail description about how to make the charger and how to find out that your charger is working okay or not but if you want to implement any indicators then its your own choice.
By providing constant voltage we will able to make our required charger. We will build a closed loop system in which our charger sense the requirement and act accordingly. We have to provide 7Ah/10 = 0.7 A current to charge the battery. I will use constant voltage technique to apply the required current. ATmega8 micro-controller which is from the family of Atmel AVR micro-controllers is used here to apply 14.4 constant volts.