mppt solar charge controller charging battery

Thread Starter

Ntombela@11620

Joined Sep 23, 2021
2
Greeting , please help me here. i am to design and build a power dc/dc converter , The converter will need to power a load (a LED floodlight) and charge a battery from a PV panel. it supposed to have the following specifications , Vinput =12V , Voutput=12V, power delivered to the load =15W.

now i have questions and need recommendations
1. How to keep the Vinput and Voutput at 12V , what do i use , what technique to use and how to intergrate it into the system?
2.where do i connect the load , before the battery or after the battery in this sequence
-PV CELL > CONVETER >BATTERY > LOAD or
- PV CELL> CONVETER >LOAD >BATTERY

3. which design software to use , most preferred

please assist me , also refer me to any site where i can see a similar done example

your input will be much appreciated
 

Ian0

Joined Aug 7, 2020
5,156
What sort of battery?
If it's lead acid, then it won't charge at Voutput =12V
What is the spec for the solar panel? Presumably the input to the converter is the output from the solar panel.
An MPPT charger doesn't have a fixed input voltage, it has to track the maximum power point (hence the acronym)
 

Thread Starter

Ntombela@11620

Joined Sep 23, 2021
2
What sort of battery?
If it's lead acid, then it won't charge at Voutput =12V
What is the spec for the solar panel? Presumably the input to the converter is the output from the solar panel.
An MPPT charger doesn't have a fixed input voltage, it has to track the maximum power point (hence the acronym)
battery is lead acid battery , and why wont it charge at 12V . which one i must use to charge 12V battery
specs of solar panel is 12V-24V at 20W.
 

Ian0

Joined Aug 7, 2020
5,156
A lead-acid battery must be charged at 2.45V/cell (12V battery has 6 cells) for boost charge, or 2.27V/cell for float charge.
See https://batteryuniversity.com/article/bu-403-charging-lead-acid
You need a datasheet for your solar panel, and it will have a set of curves like these (which are for a much larger panel):
solar.png
The aim of the MPPT is to regulate the panel voltage so that the it corresponds to the peak of the Power-Voltage curve (centre), bearing in mind that there is a large variation with temperature.
It is important that the peak of the power-voltage curve is ALWAYS at a higher voltage than the battery, even when the panel is hot. Otherwise you will need a much more complicated DC/DC converter.
Why do you need to power a floodlight from the solar panel? Won't the sunlight be bright enough?
 
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