The solar charge controller is an essential device in our solar system, especially when making use of battery backup. For us to have good charging power for our solar batteries, a charge controller must be used to regulate and deliver safe charging.
The question of what size of charge controller for 500W solar panel always arises. This is more reason we take out time to explain in detail the correct size of the charge controller for solar panels.
A 30A charge controller will best fit in for 500 watts of solar panels. This is calculated by dividing the power of the panel by the battery voltage to give us the possible current the panels can deliver. i.e. 500W/24V = 20.8A. Then add an additional 25% Amps to the calculated Amps to give us 26A. So we then round it up to 30A as it is the possible amps you can get in the market after 20A.
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How do we calculate charge controller size for solar panels?
For the fact that this article is specivically made a charge controller for a 500W panel, we will be using a 500-watt panel as a case study.
The solar charge controller for solar panels is calculated like this. The power of the panels which is measured in watts is divided by the battery voltage that is measured in Volt. Then add an additional 20-25% to the result to get the right size of the charge controller.
Let’s do it together for a 500W solar panel.
500w / 24V = 21A
Add 25% of 21A to have 26A
The common solar charge controller in the market are 10A, 20A, 30A, 40A, 50A, 60A, 80A and 100A.
So from the above chart, 20A is smaller than our calculated Amps and so we can’t choose anything below 20A. So 30A and above will serve the system. But the best fit-in for the system is the 30A controller.
When you have a 500W solar panel with a 12V battery or you configure some set of panels to give you 500W by 12V. The same procedure should be applied just that you will be dividing the watts by 12V instead of 24V.
In that case you will have 500W / 12V = 41.6A.
So if we add a 25% of 41.6 it will sum up to 52A
Then we round it up from 52A to 60A. So a 60A/12V charge controller will be the best fit for it.
Now that you know the size of the charge controller to use for a 500w solar panel. The next step is to decide the type of charge controller you will go for. Should you go for PWM or MPPT? Ok, let’s check it out and see the best one to go for.
What type of charge controller for 500W panel?
The solar charge controller is of two types, the PWM and MPPT. After calculating how many amps charge controller to use for your 500W solar panel, the next thing is to consider whether to go for PWM or MPPT.
The MPPT charge controller is the best option to use for a 500W solar panel as it is more reliable and efficient compared to PWM. The MPPT is about 30% more efficient than PWM. The two controllers are ok, but the PWM is recommended to be used for smaller panels.
Difference between PWM and MPPT controller.
lets for instance we are have a 100-watt panel and a 12-volt battery with a PWM charge controller. This is how the controller will react to the system.
The PWM controller in this case will charge the battery at the maximum battery charging volts 14.4V. A 12V battery charges at 13V, so to find out how much power from the panel that is charging the battery multiply Volts by amps. Assuming the panel lmp is 5.7A
13V x 5.7A = 74.1 watts
so from our mathematical expressions above we can see that out of the possible 100 Watts from the panel only 74.1 Watts will charge the battery. Even though, solar panels rarely generate up to their maximum power but lets assume it generate 90 watts, per hour. It is only 74.1 watts that’s charges the battery wasting about 16Watts per hour. Meaning if we use the solar panels for 5 hours, about 80W of power is wasted.
Now if 5 x 100watts solar panels are connected to a PWM charge controller. It only 370w per hour that will be charging the batteries, wasting about 500watts per hour.
If we should go for MPPT charge controller, using the same spec, the system will be well optimised and more power will go into the battery for charging.
With PWM, no matter how many volts the panels produce, is only 13V that will go into the battery for charging while the rest becomes waste. But if it should be MPPT controller, 13V will go into the battery and the rest will be converted into amps.
If a panel generate 18V and was connected to MMPT that charges at 13V.
18 / 13 = 1.38
then multiply the lmp by 1.38
5.7 x 1.38 = 7.8
Then we have 7.8 amps which when multiply by battery volt will give us the watts.
13V x 7.8A = 101.4Watts
Due the 101.4 watts is higher than the solar panel max output but since panels are not 100% efficient, the output will be lesser than 100W.
So the illustrations above is just to show how the MPPT controller is the best choice. For a smaller panels PWM will serve as the loss can be negligible but for 500W panels MPPT should be use to improve the system.
How many batteries a solar controller handle
Each system requires one charge controller that is well rated to withstand the power. But in a situation where multiple solar panels are involved, multiple controllers can be used. In terms of the 500watts panel, one charge controller (30A) is ok.
NB: the panel’s watts are divided by the battery to give us the right amps of controller. This is not only limited to 12V, and 24V single batteries. we can connect one or two batteries in series/parallel to increase amps or volts depending on what we want.
Is it must to use a charge controller for a 500W panel?
Yes, is a must as the charge controller saves your system of so many things and the same time improves the system.
below are some reasons why a charge controller Is a must used for solar installation work.
- Automatic low voltage Disconnect: The controller manages the system charging by making sure low voltage which might cause to damage the battery doesn’t go into the system.
- protection against overload: Due to the fact that the panels keep on charging the batteries as long as there is sunlight. There are no off or on buttons to turn the system on. The charge controller manags and limits the charging current to avoid damage to the system.
- Reverse current: It blocks reverse current from damaging the system.