So my friend has been asking me about MPPT and charge controller about how the output of MPPT can charge battery?
So here’s our discussion:
M: Me
SC: Sekte Cinta (Yes, it’s my friend nickname)
SC: Hi, are MPPT an algorithm to control current rate for charging battery based on max power calculated from battery voltage and current charging?
SC: for MPPT, how can make constant current and raising voltage?
M: Noooooo! MPPT is an algorithm to acquire as much power from an electric energy source which the power rated unknown. (Seriously this sentence is so compact and easy to understand once you understand what is MPPT is. Please read this sentence again after you finish this article)
SC: I am so confuse as far as I know, PV is a current source, so how can we calculate the power using resistor? saya bingung euysolar panel kan sumber arus. ngitung powernya pake R apaan?
M: Yes PV is an current source. BUT it’s power output at a time is unknown.
Please understand this! because this is why MPPT even exist!
M: Then, How can we get as much as power from this unknown power supply?
SC: Yes yes yes how?
M: just trial and error using Resistor from the big Ohmic value to small Ohmic Value. every time we connect this resistor as a load, we also measure the voltage and current (actually if we are using the known Ohmic Value of resistor we don’t need to measuring the current, but for MPPT sake we need to measure it for a reason explained later)
M: as we acquire voltage and current for any given resistor we can calculate the power acquire and compare from one resistor the rest (graphically it will show similarity to quadratic graph). Then we can estimate how much current will draw the most power out of this unknown Power Supply.
M: This Method changing resistor is actually not practical. So we can use a Variable Resistor made from Transistor (Usually MOSFET but still depend on the requirement) controlled with PWM. Then as we can control this Transistor using PWM so we can control it by any microcontroller. Since now we can use a microcontroller, then people start develop lot of method to get as much power from PV. This method or algorithm to get and track the most power then called Maximum Power Point Tracker (MPPT).
M: Perhaps a question you not asking is “Why we need to track the Maximum Power Point?”
Well, it’s because apparently Maximum Power produced by PV are not constant and we all know it. So, when it’s a shiny day, PV produce high power and when it’s cloudy day, well you know. That’s why we need to track it because PV produce non constant power.
Now, do you understand this MPPT thingy?
SC: Yes! but I still confuse about battery charger controller thing.
M: Wait, wait. This Explanation is already too long, perhaps we should continue discuss it at another post (here it is), stay tune!
Next I will write about solar charge controler and variety of DC-DC Converter and how it’s can be modeled in math also simulated in GNU-Octave.