60W MPPT Solar Charger for 14.4V LifePo4

CN3722 MPPT 14.4V LifePo4 60W Solar charger

Here is a simple circuit that I made to charge my 14.4V 4s LifePo4 battery with solar power. MPPT stands for Maximum Power Point Tracking. In a normal PWM solar charge controller, it is basically just a switch which turns on and off when the battery is full, the problem with this is the solar panel voltage drops near the battery voltage hence dropping the output power. With MPPT, it will allow the solar panel at maximum power with the maximum voltage.

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Using SNAT inverter Mode 1 for Solar

SNAT inverter has 3 modes, mode3 is basically used for solar power system and mode1 is used for UPS function. I have been using this inverter for more than a month on my home solar power setup and used it on mode3. But this mode 3 have some problems when using the inverters built-in ATS(Automatic Transfer Switch). This is the function where it automatically gets power to the grid when the battery gets very low.

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My Home Solar Power project

I have been experimenting on solar power for years but it is only recently I decided to go full speed and spent big. I want to share this project so anyone who want to DIY their home solar power project can follow.

Our country has the most expensive electricity rate in the whole south east asia so, investing in solar power is a no brainer. Sure it is a bit expensive but ROI is only around 3-4years if you do it yourself.

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Hybrid Solar Power for LED TV and Electric fan

Philippine electricity is the most expensive in south east asia and it is getting more and more expensive every month. With the solar panel getting more and more affordable, is it really worth it to invest into solar power system? How much can you save with your electricity bill with these solar power system? How much will it cost to build your own? Let’s find out!

Types of Solar power

There are basically 2 kinds of solar power system and they are 1. On-grid 2. Off-grid.

On-grid Solar Power system – basically a solar power that is tied to your existing AC power from meralco of whatever your electricity provider is. This is the simplest system since it is only tied to your existing electrical power system. It is sharing power to meralco if the power is not enough to power your house. For example if your devices or home appliance is consuming around 1000W of power in total and your solar power can only produce 600W of power, the other 400W will be supplied by Meralco. This will in turn lower your bill because you will only consume 400W instead of 1000W because your solar power will handle the rest. While if on the other scenario, if your solar power system is generating power more than you need, it will be feed the excess power to the grid and will be bought by Meralco. In this case you will be a power producer to the Meralco instead of a consumer. Meralco will pay you for the power you generated. Take note that the rate at which Meralco will pay for your generated power will be way lower than what you pay for meralco per KWhr you use. Take note also that you will need to apply for net metering so you can be able to selll your excess power to Meralco and the process is not easy. There are many documents and procedures to follow before you can qualify for net metering. If you have no net metering, you might be charged when you are producing more power than you need. This is because normal meters are not designed by bi-directional current flow. So be careful with this kind of solar power system.

image from: http://energyinformative.org

The main disadvantage of On-grid solar power system is that when there is brownout, you also experience it. This is because Electric systems on each house are connected in parallel and you solar power system will overload if it will try so power during brownouts.

Off-grid Solar Power System – by its name suggest, this is not connected to your existing electrical power system. And because it is independent by its nature, it needs a battery for powering at night when there is no sun. And batteries as all we know are not cheap! And most of all, you need to replace it very 2-3 years(depending on type of battery and usage). This makes this system more expensive as compared to On-grid systems. The main advantage of this is that you can build this system anywhere as long as there is sunshine. And the biggest advantage is that you will never experience brownout as long as your battery is in good shape.

Hybrid Solar Power – This kind of solar power is just my idea, I don’t know if someone already thought of it. But because this system is very simple, it is most likely that someone out there might already built this kind of system. Block diagram below:



I call it hybrid because the output is 12V instead of 220V compared to on-grid system and it uses your existing AC power when there is no sun to power your system. I made this system so I won’t be needing expensive battery compared to off-grid systems and won’t be supplying power to the grid compared to on-grid systems.

About the Circuit

The circuit is simple, you have 2 power sources that set at slightly different voltage. The solar panel is connected to a buck converter which reduces the voltage of the solar cell from 19V to 14V. An AC/DC switching power supply is set at around 12.7V to compensate for the diode voltage drop. The output voltage of the solar is set slightly higher so when there is enough solar power, it will pull the output voltage to around 13.3V(-0.7V diode drop), this will reverse bias the diode D2 and will act like an open circuit. If the power from the solar is not enough, both diode will conduct and the output voltage will be just around the voltage output of the AC/DC converter.

Boost converter is used to increase the voltage to 19.5V to power my 32 inch Sony LED TV. I am not sure if most of the LED TV uses 19.5V but if I remember it correctly, my LG LED TV also has 19.5V supply.

What You need

On this project, those materials can be bought from online shopping like lazada or shopee.

12V output AC/DC converter

To make it more reliable, use a type with output current double than what you require. This will reduce heat and will have longer life.

BUCK Converter with adjustable output voltage

Set the output voltage to 14V before installing this. Make sure also that it have higher output current capability than what you require.

Simple Current Sensor for Arduino and PIC

Last time I have posted a simple Current sensor for Arduino using only a resistor here in this post. But there are some problems on this kind of simple circuit and they are 1)  very lossy due to the big voltage drop on the resistor 2) if you decrease the voltage drop on the resistor, it will decrease the resolution 3) There is a significant voltage drop on the load at higher load current which is not good. The allegro current sensor ACS7xx series is a good alternative but it cost too much for my project so I search for another option.  Then I found this ZXCT1008 that is just right for my application.

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Simple Current Sensor for Arduino

There is actually a board that you can attach to arduino for measuring current but if you don’t need a very accurate measurement, you can use this very simple circuit. Usually a low resistance resistor is connected in series to the load. The voltage of the resistor is measured and divided to its resistance, the result will be current.

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