For an off-grid system, a solar battery is a very important device as it stores and delivers energy when needed. When it comes to charging it, we must select the right panel size so that your battery can charge fast without getting damaged from overload. Today, let us learn what size solar panel to charge 12V battery and how long it will take.
What Size Solar Panel to Charge 12V Battery?
For a 12V lithium-ion battery, a 150-watt solar panel can charge the device (100 Ah capacity) in 10 hours. But if you use lead acid battery, it will take a 100-watt panel.
To find the right panel wattage to charge a 12V battery, you must answer these two questions:
- What is your battery capacity in amperage?
- How quickly do you want to charge it?
If we talk about the general principle, the size of solar panels should be such that it provides 1.5 to 2 times the battery’s capacity in watts.
Now to precisely calculate, we will follow these steps:
Step 1: We will first need to find the wattage by multiplying the amps and voltage. (Amp/hr x Voltage) = Watts
Step 2: We will divide watts by the recharge time in peak sun hours. Watts/recharge time in peak sun hours = Size of solar panel needed
Though it looks simple, the question about the size of the panel depends on:
- Hours of sunshine over the area: Areas with more hours of sunshine would provide more time for the battery to charge. So, the panel with a lower capacity may also work unlike for the areas with less sunshine.
- Intensity of sun: A bright sunny place will generate more energy and it will take only a few small size panels.
- Types of solar panel: You can use mono-crystalline solar panels as they are more efficient than poly-crystalline ones.
- Battery capacity in amps: It represents the amps it can supply in an hour. So, if a battery has higher amperage it can store more and thus would require more power to charge.
How long does it take a 100W Solar Panel to Charge 12V Battery?
It is quite a wide range between 22.8 minutes to 76.8 hours. But to ascertain the exact time we need to look upon majorly two major factors – battery capacity and peak sun hours. In the case of a higher capacity battery with greater peak sun hours, the time consumed to charge fully would be less and vice versa.
For the precise calculation, here are the steps:
Step 1: First, we need to convert the battery capacity from Ah into watts. For this we can use the basic formula i.e. amperage x voltage = watts. Here let us take the example of a 12V battery with 50 amp, it requires 50 x 12 = 600W
Step 2: Then we need to ascertain the output per hour by the solar panel on an average. For a 100-watt panel with 5 peak sun hours and 25% average loss of energy ( or 0.75 ), we can calculate watt per hour as 100W x 5h x 0.75 = 375W/day which is equal to 31.25 watt/h.
Step 3: Now finally, for charging time you will have to divide the battery capacity in watts by electricity production in watts/hr. Here we can say that for a 12V 50amp battery to be charged with a 100-watt solar panel.
Required time = 600 Watt / 31.25wh = 19.2 hrs.
Also, check out How to Connect 18V Solar Panel to Charge 12V Battery
How to Charge 12V Battery with Solar Panel
Here are the charging steps for a 12 V battery.
Step 1: You can connect the panel to the controller using the proper cables. Attach the positive cable to the positive panel adapter cable and vice-versa. Then plug the positive solar input cable into the positive solar PV terminal, tighten it and connect the negative in the same manner.
Step 2: Now, connect the charge controller to the battery with appropriate wires. For this, you need to connect the positive battery with the positive terminal and the negative with the negative one by attaching the stripped end. The bare wire end has to be inserted in the charge controller port. Ensure to tighten them with a screwdriver.
Step 3: Once the connection is established position the solar panel in a position to face directly to the sun such that it receives maximum sunlight. Allow it to charge fully.
Cross-reference: How to Wire Solar Panel to 12V DC Load and Battery?
What Size Solar Panel to Charge 24V Battery?
You can use a 190 watt panel and charge a 100 Ah battery in 10 hours.
If interested, take a look at What Size Solar Panel to Charge a 50Ah Battery?
Can You Charge 48V Battery with 12V Solar Panel?
Yes, you can but the small size panel produces much less energy. This may take a long time to charge the battery and can damage it to some extent. Here, you can use two or more panels in series to charge the battery.
What Size Solar Panel to Charge 48V Battery?
You can use a 380 watt panel and charge the same battery in 10 hours.
Now you know what size solar panel is needed to charge a 12V battery and its process. We also discussed factors like battery capacity, peak sun hours, and the type of solar panel that affect its size selection. This guide will hopefully help you to effectively charge your battery without the risk of damaging it.
Recommended: How to Convert 24V Solar Panel to 12V Battery
