Please do not try to modify the PCB circuit unless you are a professional technician. And we are not responsible for such a result. The best working time: 9:00-17:00 (mainly for sunlight weather).Which is intended to extend the battery life and emergency charge usage. Please choose other higher current products if you want a faster charging speed. Please don't scratch the surface of the solar panel with a sharp object. Please make the solar panel exposed to direct sunlightto ensure the best charging speed while it is charging. Please don't place the charger in the rainny day, or it will lead to a short circuit. The 18V100W solar panel charger is built with an Anti-flow resistense preventerinsdie, it will not occur the backflow phenomenon. The main function of this product is to charge the 18V battery of car, moto and motorboat or most of the 12V lead-acid and lithium batteries. The trickle charging will be helpful for extending the battery life though its current is small. The charging method is not only energy saving, maintain battery life, but also can meet the needs of some small capacity car audios, which it's very suitable for outdoor work, travel or camping. 18V car, batteries and so on. The item "300W 18V Flexible Monocrystalline Solar Panel Power Charging RV Caravan Boat W" is in sale since Saturday, November 21, 2020. This item is in the category "Home & Garden\Home Improvement\Electrical Supplies\Alternative Energy Supplies\Solar Power Supplies\Solar Panels & Kits". The seller is "haver17" and is located in Shenzhen. This item can be shipped worldwide.