The short answer to this question is Yes, you can charge a 12v battery with an 18v solar panel.
But connecting a different volt solar panel directly to a 12v battery can damage the battery permanently
18v solar panel will produce 22-25 volts under ideal direct sunlight conditions (open circuit voltage).
Which you can see on the backside of your solar panel. So now it’s not even 18V but 24-25v so how can you charge your 12v battery with this 24v output from the solar panel
How To Connect Different Volt Solar Panel To 12v Battery?
12v batteries are rated to be charged at 12v or a maximum of 14 volts depending on the type of battery and its state of charge.
A fully drained battery will accept higher voltage but as the battery will get charged the input voltage limit will decrease
so if you’ll connect a 12v or 24v solar panel directly with the battery it may damage the battery permanently
And keep that in mind that this kind of damage will not be covered in the warranty
so here are some devices which you can use to charge different sizes of solar panels with a 12v battery
1- Use a charge controller
The solar charge controller is a device that regulates the voltage coming from the solar panels according to battery voltage.
For example, in this case, if you have an 18v solar panel with a 12v battery so a charge controller will drop the 18 volts coming from the solar panel to 12 volts to charge the battery
That’s the basic job of a charge controller or solar regulator in simple words, but there are two types of charge controllers available PWM and MPPT charge controller which one is better?
PWM charge controller:
in simple words, a PWM charge controller will drop down the higher voltage coming from the solar panels to match the voltage of the battery but the amps will stay the same which makes them less efficient and will cause a loss of power. here’s how
Total power is measured in watts so to calculate watt multiply volts with amps (Watts = volts * amps)
And we know that an 18V 100W solar panel will produce 25v (open circuit voltage) under ideal sunlight conditions so to calculate amps (Amps = watts/volts) 100/25 = 4.1 Amps
you’ll receive 4.1 amps from an 18v 100w solar panel under standard test conditions.
So in this case the PWM charge controller will drop down the voltage to 12v but the amps will stay the same (4.1) so 4. 1* 12 = 50 watts
Woah, where did the rest of the 50 watts gone? we’ll you lost them because of PWM charge controller. So here’s the MPPT charge controller comes into action
The MPPT charge controller
has a built-in computer brain in it which will adjust the voltage output from solar panels according to battery voltage but also will increase the amps accordingly which makes them 30% more efficient than the PWM Charge controller
So if you’re using an 18v or 24v or even 48v solar panel to charge your 12v battery I would recommend using an MPPT charge controller
With a 12v solar panel to charge a 12v battery, you can go for a PWM charge controller but still, there will be some power losses
2- Use Converter (DC-DC)
A DC-DC converter is a device like a cheaper version of a charge controller. This converter will also decrease the high voltage coming from the solar panels down to 12v to charge a 12v battery.
But like PWM charge controllers they’ll cause a power loss. the difference will matter a lot if you’re using a large-size solar panel
But you can have this device for a small solar panel like 20W or 50W. you’ll still face some power loss but this will not be much.
Video – Charging 12v battery with 24v solar panel
Can I Connect Different volt Solar Panel Directly To Battery?
if you’re using a 5W solar panel then yes you can connect different voltage solar panels directly to the battery.
But, for more than a 5w solar panel you have to use a charge controller which will regulate the voltage coming from the solar panel in order to charge the battery.
Otherwise, connecting a solar panel that is higher than 5W directly with the battery can damage the battery permanently
Related Post: Maximum Charging Current & Voltage For 12v Battery
Related Post: How Long To Charge 12v Battery With Solar panel?
With the help of a charge controller or DC-DC converter you can use an 18v or 24v solar panel to charge a 12v battery, MPPT charge controller will be more efficient in this case
I hope this short post was helpful to you if you have any queries contact us thank you!