A solar trickle charger is a great way to keep your car battery charged and ready to go. However, you may be wondering if it is safe to leave the charger on all the time. The answer is yes, you can leave a solar trickle charger on all the time as long as it is getting enough sunlight to charge the battery. If you are concerned about overcharging the battery, there are some models that come with an automatic shut off feature that will turn the charger off when the battery is fully charged.