Solar charge controllers come in several sizes and capacities (watts). For instance, you may have the smaller 10 watt solar panel available on your RV or laying around.
What can such a low power solar panel be used for? Can it overcharge a battery? Does it need a charge controller?
Read on to find out if you need a charge controller for the smaller 10 watt solar panel and what it is best suited for.
Does a 10 watt Solar Panel Need a Charge Controller?
With the larger capacity automotive batteries, a 10 watt solar panel may not need a controller given its low output current of about 0.83 amps at peak sunshine.
The solar panel helps offset the current draw from the onboard car electrical systems when the car alternator/engine is not running. That said, some 10 watt solar panels come with inbuilt charge controllers.
Can a 10-Watt Solar Panel Overcharge the Battery?
The output voltage of some solar panels may be unregulated which increase the risk of overcharging the battery if the solar panel does not have an inbuilt charge controller or is not connected to a charge controller.
Use a solar panel with a charge controller, to avoid the risk of overcharging.
You can use a 5 amp charge controller or larger to regulate the charging voltage from the panel.
How Many Amps from the Solar Panel?
The estimated output current from a 10 watt solar panel at 12V is about 0.83 amps.
Typical current from the panel at 18V may be only 0.5 amps under peak sunshine. Actual output current may be lower if the panels receive less sunshine.
How Long to Charge a 12V Battery?
Do not count on a 10 watt solar panel to charge a drained battery, its output current is very low and it would take several hundred hours to fully charge it.
The solar panel is best suited to maintaining an already fully charged car battery.
What to Use it for?
10-watt solar panels are usually used as trickle chargers or battery maintainers to keep a 12V car, boat, truck battery topped up when it is going to be parked for several days or weeks.
Without one, the car battery loses charge overtime to self discharge and the parasitic draw from the connected accessories such as sensors, alarms or other.
To keep the battery topped up, make sure the solar panel is facing the sun. Connect the solar panel alligator clips to connect to the car battery posts or the cigarette lighter plug (if available) into a cigarette lighter socket.
Make sure to connect the positive solar panel battery clip to the positive battery post and the negative solar panel battery clip to the negative battery post to charge the battery.
Connecting a 10 watt solar panel directly to a 12V battery risks overcharging it.
Use one with an inbuilt charge controller or use an external 5 amp charger or larger.