If you’re planning to set up a solar panel system to charge a 12-volt battery, you’ll need an charge controller to regulate the charging process. One of the first questions you will face is whether to choose a PWM or MPPT controller. Once you’ve decided on that, the second question is what size controller you should choose (referred to in ‘Amps’).Â
Correctly calculating the size of an MPPT charge controller is essential to ensure that it can handle the current generated by your solar panel array and efficiently charge your battery.
Maximizing Efficiency: Why dividing by 14.4v is Key in MPPT Controller Sizing
While it’s common practice to divide the solar panel wattage by the battery voltage to determine the minimum size of your charge controller, this is slightly misleading. Many blog posts will tell you to divide your solar panels wattage by your battery’s voltage.
For example, let’s say you have a 200-watt solar panel array and a 12-volt battery bank. Using the formula above, the minimum size of the MPPT charge controller would be:
When calculating the size of an MPPT charge controller for a 12-volt battery, it’s crucial to use a charging voltage of 14.4 volts NOT 12 volts. The reason for this is that a 12-volt battery needs a charging voltage that is higher than its nominal voltage to fully charge it.
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What does that mean in non-chinese?
Think of current flow like water flowing in a river. Just like water flows from a higher altitude to a lower altitude, electricity flows from a higher voltage to a lower voltage. It’s like water flowing downhill – the higher the altitude, the more potential energy the water has, and the faster and stronger it flows. Similarly, the higher the voltage in an electrical circuit, the more potential energy the electricity has, and the faster and stronger it flows through the circuit.
So, just as water flows from high to low, electricity flows from high voltage to low voltage in a circuit. This is why it’s important to have the right voltage in a circuit, so that the electricity can flow to the device or equipment you need to power.
A fully charged 12-volt lead-acid battery typically has a voltage of around 12.6 volts, and the charging voltage needs to be higher than this to overcome the internal resistance and ensure a full charge. The recommended charging voltage for a 12v lead-acid, therefore, is typically around 14.4 volts, and this is the voltage that should be used when calculating the size of an MPPT charge controller for a 12-volt battery.
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Correctly calculating the size of an MPPT controller
To calculate the minimum size of an MPPT charge controller for a 12-volt battery, you should use the following formula:
Minimum MPPT Charge Controller Size (in amps)Â =Â
(Maximum Solar Panel Wattage) / (Charging Voltage of the Battery)
For example, let’s say you have a 200-watt solar panel array and a 12-volt battery bank. Using the formula above, the minimum size of the MPPT charge controller would be:
Minimum MPPT Charge Controller Size (in amps) =Â
(200 watts) / (14.4 volts) = 13.89 amps
In this case, you would need a charge controller with a minimum rating of 13.89 amps to effectively charge the 12-volt battery bank using the 200-watt solar panel array. That’s better for you as you don’t need to fork out for such a large controller!
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If you are thinking of getting an MPPT controller, check out Voltanic controllers below. They are some of the best priced highest quality controllers available on the market today.
2 replies to “Avoiding Common Mistakes: Why Dividing by 14.4V is Key in MPPT Controller Sizing”
Jeff
Hello,
I have a battery bank of 24v @ 500 Amps ( I have Hybrid T-gel deep cycle batteries). I basically run on 300 Amps so that I don’t drain the batteries. What do you recommend what the mppt controller amperage should be, as well as pv wattage.
I was planning to use PowMr Mppt 60A with 2 – 550w panels.what do you think?
Hello Jeff,
Yes that sounds like it will work. 2x 550w panels will give you 1100 watts of power. Your battery is 24v so you divide the watts by the voltage of your battery (1100/28.8) giving you 38.19 amps. Meaning your 60A MPPT will handle that. Hope that helps 🙂
Cheers
Avoiding Common Mistakes: Why Dividing by 14.4V is Key in MPPT Controller Sizing
If you’re planning to set up a solar panel system to charge a 12-volt battery, you’ll need an charge controller to regulate the charging process. One of the first questions you will face is whether to choose a PWM or MPPT controller. Once you’ve decided on that, the second question is what size controller you should choose (referred to in ‘Amps’).Â
Correctly calculating the size of an MPPT charge controller is essential to ensure that it can handle the current generated by your solar panel array and efficiently charge your battery.
Maximizing Efficiency:
Why dividing by 14.4v is Key in MPPT Controller Sizing
While it’s common practice to divide the solar panel wattage by the battery voltage to determine the minimum size of your charge controller, this is slightly misleading. Many blog posts will tell you to divide your solar panels wattage by your battery’s voltage.
For example, let’s say you have a 200-watt solar panel array and a 12-volt battery bank. Using the formula above, the minimum size of the MPPT charge controller would be:
MPPT Controller Size (in amps) = (200 watts) / (12 volts) = 16.67 amps
This is wrong!
When calculating the size of an MPPT charge controller for a 12-volt battery, it’s crucial to use a charging voltage of 14.4 volts NOT 12 volts. The reason for this is that a 12-volt battery needs a charging voltage that is higher than its nominal voltage to fully charge it.
Â
Â
What does that mean in non-chinese?
Think of current flow like water flowing in a river. Just like water flows from a higher altitude to a lower altitude, electricity flows from a higher voltage to a lower voltage. It’s like water flowing downhill – the higher the altitude, the more potential energy the water has, and the faster and stronger it flows. Similarly, the higher the voltage in an electrical circuit, the more potential energy the electricity has, and the faster and stronger it flows through the circuit.
So, just as water flows from high to low, electricity flows from high voltage to low voltage in a circuit. This is why it’s important to have the right voltage in a circuit, so that the electricity can flow to the device or equipment you need to power.
A fully charged 12-volt lead-acid battery typically has a voltage of around 12.6 volts, and the charging voltage needs to be higher than this to overcome the internal resistance and ensure a full charge. The recommended charging voltage for a 12v lead-acid, therefore, is typically around 14.4 volts, and this is the voltage that should be used when calculating the size of an MPPT charge controller for a 12-volt battery.
Â
Â
Â
Correctly calculating the size of an MPPT controller
To calculate the minimum size of an MPPT charge controller for a 12-volt battery, you should use the following formula:
Minimum MPPT Charge Controller Size (in amps)Â =Â
(Maximum Solar Panel Wattage) / (Charging Voltage of the Battery)
For example, let’s say you have a 200-watt solar panel array and a 12-volt battery bank. Using the formula above, the minimum size of the MPPT charge controller would be:
Minimum MPPT Charge Controller Size (in amps) =Â
(200 watts) / (14.4 volts) = 13.89 amps
In this case, you would need a charge controller with a minimum rating of 13.89 amps to effectively charge the 12-volt battery bank using the 200-watt solar panel array. That’s better for you as you don’t need to fork out for such a large controller!
Â
Â
If you are thinking of getting an MPPT controller, check out Voltanic controllers below. They are some of the best priced highest quality controllers available on the market today.
2 replies to “Avoiding Common Mistakes: Why Dividing by 14.4V is Key in MPPT Controller Sizing”
Jeff
Hello,
I have a battery bank of 24v @ 500 Amps ( I have Hybrid T-gel deep cycle batteries). I basically run on 300 Amps so that I don’t drain the batteries. What do you recommend what the mppt controller amperage should be, as well as pv wattage.
I was planning to use PowMr Mppt 60A with 2 – 550w panels.what do you think?
Thanks,
Jeff Dorfman
jason
Hello Jeff,
Yes that sounds like it will work. 2x 550w panels will give you 1100 watts of power. Your battery is 24v so you divide the watts by the voltage of your battery (1100/28.8) giving you 38.19 amps. Meaning your 60A MPPT will handle that. Hope that helps 🙂
Cheers